The session welcomes papers on:

1) Forecasting and simulating high impact weather events - research on improvement of high-resolution numerical model prediction of severe weather events (such as winter storms, tropical storms, and severe mesoscale convective storms) using data from various observational platforms, evaluation of the impact of new remote sensing data;

2) Development and improvement of model numerics - basic research on advanced numerical techniques for weather and climate models (such as cloud resolving global model and high-resolution regional models specialized for extreme weather events on sub-synoptic scales);

3) Development and improvement of model physics - progress in research on advanced model physics parametrization schemes (such as stochastic physics, air-wave-oceans coupling physics, turbulent diffusion and interaction with the surface, sub-grid condensation and convection, grid-resolved cloud and precipitation, land-surface parametrization, and radiation);

4) Model evaluation - verification of model components and operational NWP products against theories and observations, regional and global re-analysis of past observations, diagnosis of data assimilation systems;

5) Data assimilation systems - progress in the development of data assimilation systems for operational applications (such as reanalysis and climate services), research on advanced methods for data assimilation on various scales (such as treatment of model and observation errors in data assimilation, and observational network design and experiments);

6) Ensemble forecasts and predictability - strategies in ensemble construction, model resolution and forecast range-related issues, and applications to data assimilation;

7) Advances and challenges in high-resolution simulations and forecasting.

This session will focus on weather forecasting and aviation meteorology, particularly related to high impact weather conditions, as well as the ones that affect aviation operations.
Recent research and developments on forecasting techniques and in-situ observations, in particular those related to operations and impact scenarios will be considered for submission. In addition to nowcasting, meso-scale, ensemble prediction, and statistical post-processing models, applications of these to aviation operations will also be considered. Airports and flights are affected by the poor weather conditions including low visibilities, strong wind shear and turbulence, and heavy rain or snow. Extreme weather conditions impact sensor performance, and the ability of airborne systems to maintain flight operations are critical for flights, and specifically for UAVs. Poor weather and associated airport conditions create challenges to the aviation Industry and results in billion dollars of financial loss.
In situ and remote sensing observations of weather, prediction by NWP models and integrated systems, as well as artificial intelligence/machine learning and aviation weather decision support systems are becoming important for aviation operations and decision making. This session will bring researchers together to discuss NWP model development for high impact weather and its application to aviation meteorological issues to reduce risk and adverse weather conditions.

Key Words: NWPs, Aviation meteorology, in-situ observations, forecast technique, nowcasting, convection permitting modelling, ensemble prediction, integrated weather observing systems,

Weather and climate models used for weather forecasts, seasonal predictions and climate projections, are essential for decision making on timescales from hours to decades. However, information about future weather and climate relies on complex, though imperfect, numerical models of the Earth-system. Systematic biases and random errors have detrimental effects on predictive skill for dynamically driven fields on weather and seasonal time scales. Biases in climate models also contribute to the high levels of uncertainty in many aspects of climate change as the biases project strongly on future changes. A large source of uncertainty and error in model simulations is unresolved processes, represented through parameterization schemes. However, these errors typically materialize at large spatial scales. Our physical understanding of the mechanical and dynamical drivers of these large-scale biases is incomplete. Incomplete mechanistic understanding hinders marked improvements in models, including identification of the parameterizations most in need of improvement.

Understanding and reducing the errors in weather and climate models due to parameterizations and poorly represented mesoscale to regional scales processes is a necessary step towards improved weather and climate prediction. This session aims to bring together these two perspectives, and unite the weather and climate communities to address this common problem and accelerate progress in this area.

This session seeks submissions that aim to quantify, understand, and reduce sources of error and bias in weather and climate models. Themes covered in this session include:

- Theory and development of parameterization. Impact on errors in mean state, model variability and physical process representation;

- Improved physical understanding of the drivers of large-scale biases including the use of process studies, idealized modeling studies and studies with strong observational components;

- Growth and propagation of error and bias in models; model errors across temporal and spatial scales; dependency of errors on model resolution and the development of scale-aware parameterization schemes;

- Use of “emergent constraints” to relate present day model biases with the climate change signal;

- Understanding and representing random model error.

Invited presentations: Felix Pithan (AWI) and Bob Plant (University of Reading)

Lead Convenors: Hannah Christensen and Stefan Sobolowski
Co-convenors: Craig Bishop, Ariane Frassoni, Daniel Klocke, Erica Madonna, Isla Simpson, Keith Williams, Giuseppe Zappa

The quality of predictions of weather and climate depends on both resolution and complexity of the models that are used. However, resolution and complexity are limited by the computational performance that is available on today's supercomputers. While weather and climate models run on some of the fastest supercomputers of the world, models typically fail to run close to peak performance such that there is still room for a significant speed-up if efficiency is improved. The increase in parallelisation in high performance computing and the availability of various computing platforms is imposing significant challenges for the community to find the optimal hardware/model configuration and to achieve the best performance. On the other hand, the evaluation of high resolution simulations is often tedious due to large data volumes, limited statistic that is affordable and changed model behaviour that needs to be studied (e.g. if convection or eddies are resolved explicitly or if non-hydrostatic equations need to be used).
These challenges can only be addressed appropriately in a close collaboration between Computing and Earth System Scientists. This session aims to bring together scientists who run and evaluate atmosphere and ocean models with high resolution and complexity as well as scientists who enable these models to run as efficiently as possible on existing and future high performance computing architectures (regarding both model development and model optimisation). The session will also be an opportunity for scientists from the EU projects PRIMAVERA, ESCAPE and ESiWACE as well as HighResMIP from CMIP6 to meet and interact.

V. Balaji from Princeton University will be our keynote speaker invited by the ESiWACE EU Horizon2020 COE (grant number 675191).

From the perspective of Earth System predictions, the use of machine learning, and in particular deep learning, is still in its infancy. There are many possible ways how machine learning could improve model quality, generate significant speed-ups for simulations or help to extract information from numerous Earth System data, in particular satellite observations. However, it has yet to be shown that machine learning can hold what it is promising for the specific needs of the application of Earth System predictions. This session aims to provide an overview how machine learning can/will be used in the future and tries to summarise the state-of-the-art in an area of research that is developing at a breathtaking pace.

The WMO World Weather Research Programme (WWRP)–World Climate Research Programme (WCRP) Sub-seasonal to Seasonal (S2S) Prediction Project has the goal of improving forecast skill of the 2 week to 2 month lead time range and now provides research communities with unprecedented access to a comprehensive database of forecasts and hindcasts from a large number of forecasting centres from across the globe.

This session invites contributions that span all aspects of S2S meteorological, hydrological and oceanographic prediction, including impacts studies that may or may not make use of the S2S databases.

Specifically we welcome contributions that focus on phenomena such as

- The Madden Julian Oscillation (MJO)
- Tropical/extra-Tropical waves
- Stratospheric variability and stratosphere -troposphere coupling
- Predictability and skill of atmospheric or surface variables
- Transition of weather regimes
- Case studies of extreme weather events on the S2S scale

Contributions regarding impacts studies at the S2S time-range are also highly welcome, including the areas of water management (e.g floods, drought), health (vector-borne diseases, heat waves, air quality) and security (fires), agriculture and energy. These can include modelling studies of the impacts through to presentations of how S2S-derived information can be integrated into decision support systems at the local, regional and country level.

*********** UPDATE ********************

Solicited talks:

Dr Andrea Manrique-Suñén from Barcelona Supercomputer Centre (BSC) will talk about the S2S4E project which aims to bring sub-seasonal to seasonal climate predictions to the renewable energy sector. To illustrate the potential benefits of S2S predictions the S2S4E projects have analysed several case studies, i.e. periods pointed out by the energy companies as having an unusual climate behavior that affected the energy market. Two of these case studies show how the climate predictions of each event would have helped stakeholders to take precautionary actions several weeks ahead.

Dr Andrew Robertson from Columbia University will give a review of the status of the S2S project, and show some examples of the sub-seasonal forecast products which have been developed at IRI

Statistical post-processing techniques for weather, climate, and hydrological forecasts are powerful approaches to compensate for effects of errors in model structure or initial conditions, and to calibrate inaccurately dispersed ensembles. These techniques are now an integral part of many forecasting suites and are used in many end-user applications such as wind energy production or flood warning systems.

Many of these techniques are now flourishing in the statistical, meteorological, climatological, hydrological, and engineering communities. The methods range in complexity from simple bias correction up to very sophisticated distribution-adjusting techniques that take into account correlations among the prognostic variables.

In this session, we invite papers dealing with both theoretical developments in statistical post-processing and evaluation of their performances in different practical applications oriented toward environmental predictions.

Recent years have seen a substantial progress in the understanding of the nonlinear and stochastic processes responsible for important dynamical aspects of the complex Earth system. The Earth system is a complex system with a multitude of spatial and temporal scales which interact nonlinearly with each other. For understanding this complex system new methods from dynamical systems, complex systems theory, complex network theory, statistics and climate and Earth sciences are needed.

In this context the session is open to contributions on all aspects of the nonlinear and stochastic dynamics of the Earth system, including the atmosphere, the ocean and the climate system. Communications based on theoretical and modeling studies, as well as on experimental investigations are welcome. Studies that span the range of model hierarchy from idealized models to complex Earth System Models (ESM), data driven models, use observational data and also theoretical studies are particularly encouraged.

Invited speaker: Cecile Penland (NOAA)

Wind and solar power are the predominant new sources of electrical power in recent years. Solar power reached a milestone of providing 50% of demand in Germany during one hour in 2012, and wind power during one hour in 2015 exceeded 140% of demand in Denmark. By their very nature, wind and solar power, as well as hydro, tidal, wave and other renewable forms of generation are dependent on weather and climate. Modelling and measurement for resource assessment, site selection, long-term and short term variability analysis and operational forecasting for horizons ranging from minutes to decades are of paramount importance.

The success of wind power means that wind turbines are increasingly put in sites with complex terrain or forests, with towers extending beyond the strict logarithmic profile, and in offshore regions that are difficult to model and measure. Major challenges for solar power are notably accurate measurements and the short-term prediction of the spatiotemporal evolution of the effects of cloud field and aerosols.

For both solar and wind power, the integration of large amounts of renewable energy into the grid is another critical research problem due to the uncertainties linked to their forecast and to patterns of their spatio-temporal variabilities.
Of particular interest these days is the relatively new field of urban meteorology applied to the renewable energy sector. There are several “Smart Cities” and “Smart Grids” projects in Europe focusing on urban modelling and measurement development for forecasts or high resolution resource mapping.

We invite contributions on all following aspects of weather dependent renewable power generation:

• Wind conditions (both resources and loads) on short and long time scales for wind power development, especially in complex environments (e.g. mountains, forests, coastal or urban).
• Long term analysis of inter-annual variability of solar and wind resource
• Typical Meteorological Year and probability of exceedance for wind and solar power development,
• Wind and solar resource and atlases.
• Wake effect models and measurements, especially for large wind farms and offshore.
• Performance and uncertainties of forecasts of renewable power at different time horizons and in different external conditions.
• Forecast of extreme wind events and wind ramps.
• Local, regional and global impacts of renewable energy power plants or of large-scale integration.
• Dedicated wind measurement techniques (SODARS, LIDARS, UAVs etc.).
• Dedicated solar measurement techniques (pyranometric sensors, sun-photometer, ceilometer, fish-eye cameras, etc.) from ground-based and space-borne remote sensing.
• Tools for urban area renewable energy supply strategic planning and control.

Papers are solicited related to the understanding and prediction of weather, climate and geophysical extremes, from both an applied sciences and theoretical viewpoint.

In this session we propose to group together the traditional geophysical sciences and more mathematical/statistical approaches to the study of extremes. We aim to highlight the complementary nature of these two viewpoints, with the aim of gaining a deeper understanding of extreme events.

Potential topics of interest include but are not limited to the following:

· How extremes have varied or are likely to vary under climate change;
· How well climate models capture extreme events;
· Attribution of extreme events;
· Emergent constraints on extremes;
· Linking dynamical systems extremes to geophysical extremes;
· Geophysical flows as a dynamical system: classification of large-scale flows and metastable states;
· Advances in diagnosing local and mean properties of the climate system as a dynamical system (e.g. maximum entropy production principles);
· Extremes in dynamical systems;
· Dynamical systems metrics as indicators of climate change;
· Dynamical downscaling of weather and climate extremes.

Confirmed Invited Speakers are:
-David Barriopedro (Complutense University of Madrid, Spain)
-Pascale Braconnot (IPSL, France)
-Nikki Vercauteren (Freie Universitaet Berlin, Germany)

Today, it is almost certain that global climate change will affect the frequency and severity of extreme meteorological and hydrological events. It is necessary to develop models and methodologies for the better understanding, forecasting, hazard prevention of weather induced extreme events and assessment of disaster risk. This session considers extreme events that lead to disastrous hazards induced by severe weather and climate change. These can, e.g., be tropical or extratropical rain- and wind-storms, hail, tornadoes or lightning events, but also floods, long-lasting periods of drought, periods of extremely high or of extremely low temperatures, etc. Papers are sought which contribute to the understanding of their occurrence (conditions and meteorological development), to assessment of their risk and their future changes, to the ability of models to reproduce them and methods to forecast them or produce early warnings, to proactive planning focusing to damage prevention and damage reduction. Papers are also encouraged that look at complex extreme events produced by combinations of factors that are not extreme by themselves. The session serves as a forum for the interdisciplinary exchange of research approaches and results, involving meteorology, hydrology, hazard management and/or applications like insurance issues.

The polar climate system is strongly affected by interactions between the atmosphere and the cryosphere. Feedback mechanisms between snow, land ice, sea ice and the atmosphere, such as blowing snow, ice melt, polynya formation, and sea ice production play an important role. Atmosphere-ice interactions are also triggered by synoptic weather phenomena such as cold air outbreaks, katabatic winds, polar lows, atmospheric rivers, Foehn winds and heatwaves. However, our understanding of these processes is still incomplete, and to fully capture how atmosphere, land ice and sea ice are coupled on different spatial and temporal scales, remains a major challenge.
This session will provide a setting to foster discussion on the atmosphere-ice coupling in both the Northern and Southern Hemispheres. It will offer the opportunity to review newly acquired knowledge, identify gaps, and which instruments, tools, and studies can be designed to address these open questions.
We invite contributions on all observational and modelling aspects of Arctic and Antarctic meteorology and climatology that address atmospheric interactions with the cryosphere. This may include studies of atmospheric dynamics that influence sea-ice dynamics or ice-sheet mass balance, or investigations into the variability of the atmospheric circulation such as polar jets, the circumpolar trough, storm tracks and their link to changes in the cryosphere.

The North Atlantic exhibits a high level of natural variability from interannual to centennial time scales, making it difficult to extract trends from observational time series. Climate models, however, predict major changes in this region, which in turn will influence sea level and climate, especially in western Europe and North America. In the last years, several projects have been focused on the Atlantic circulation changes, for instance OVIDE, RACE, OSNAP, and ACSIS. Another important issue is the interaction between the atmosphere and the ocean as well as the cryosphere with the ocean, and how this affects the climate.
We welcome contributions from observers and modelers on the following topics:

-- climate relevant processes in the North Atlantic region in the atmosphere, ocean, and cryosphere
-- response of the atmosphere to changes in the North Atlantic
-- atmosphere - ocean coupling in the North Atlantic realm on time scales from years to centuries (observations, theory and coupled GCMs)
-- interpretation of observed variability in the atmosphere and the ocean in the North Atlantic sector
-- Comparison of observed and simulated climate variability in the North Atlantic sector and Europe
-- Dynamics of the Atlantic meridional overturning circulation
-- variability in the ocean and the atmosphere in the North Atlantic sector on a broad range of time scales
-- changes in adjacent seas related to changes in the North Atlantic
-- role of water mass transformation and circulation changes on anthropogenic carbon and other parameters
-- linkage between the observational records and proxies from the recent past

Invited Speakers: Professor Ric Williams, University of Liverpool, UK
Dr. Arnaud Czaja, Imperial College, London, UK

This session invites contributions on all aspects of dynamical meteorology, especially into the investigation of mid-latitude cyclone and storms on both hemispheres. The session focuses on predictability of mid-latitude, tropical and polar weather systems, including cyclones at different stages of their life cycles from the initial development, to the large-scale and synoptic-scale conditions. Factors influencing cyclone growth to a severe storm, up to their dissipation are investigated from dynamical as well as climatological perspectives. This session will focus on all aspects of cyclone activity (including their impacts) and mid-latitude dynamical meteorology, particularly inviting results from recent field campaigns.
One goal of the session is to bring researchers together from different areas of expertise and backgrounds: researchers from dynamic-climatological perspectives and end-users and practitioners from impact based research and applications (e.g. financial sector, insurance industry).

From interannual to multidecadal time scales, there is strong climate variability over both the tropical and extratropical regions of the globe. Several modes of both extratropical atmospheric circulation (NAM/AO, NPO, PNA, NAO, SAM/AAO, etc.) and sea surface temperature (AMO, PDO, North Pacific Gyre Oscillation (NPGO), North Atlantic tripole (NAT), etc.) have been proposed to explain the extratropical climate variability. These modes have profound impacts on the global and regional climates (i.e., temperature, precipitation, frequency of high-impact weather/climate events such as hurricane/typhoon, drought/flood and cold/heat waves, etc.). The associated dynamics and physical processes, such as the ocean-atmosphere interaction, coupled oceanic-atmospheric bridge, atmospheric internal dynamics and oceanic dynamics, are important for understanding the tropical-extratropical climate variability and thus have implications for the interannual to decadal predictability. However, the relevant dynamics and processes are not very well represented in current climate system models. Often this is due to a lack of observations of the processes being modelled. Contributions are welcome from, but not limited to, research on observational, theoretical and modeling studies on the following topics:
1. Physical processes and dynamics in the atmosphere/ocean and atmosphere-ocean coupling associated with the tropical-extratropical climate variability on time scales from years to multi-decades.
2. The impacts and teleconnections of the tropical-extratropical climate variability on a broad range of time scales and underlying physical mechanisms.
3. Comparison of observed and simulated tropical-extratropical climate variability and its climate impacts.
4. Predictability, prediction and projection of tropical-extratropical atmospheric and oceanic variability at various time scales.

This session aims to investigate the end-to-end process from remote teleconnections, either Arctic or Tropical, to how these affect the predictability of NH weather patterns and the influence of these patterns on the NH. The goal of the session is to bring together researchers who contribute to the inter-disciplinary science of remote teleconnections of NH Winter dynamics and their predictability.

Papers on the following topics are invited:
• Mid-high latitude response to remote teleconnections
• Processes affecting the predictability of the NH weather patterns
• Understanding the impact on NH weather patterns
• The effect of climate change on these processes

Geophysical Fluid Dynamics (GFD) deals with various aspects of the mathematical descriptions of rotating stratified fluids starting from the physical laws of hydro-thermo-dynamics. Physicists and Mathematicians originating from various disciplines developed physical and numerical models with increasing complexity, adding to our fundamental understanding of such flows and thereby unifying these fields. Today GFD is a truly interdisciplinary field of its own, which encompasses multiscale flows of planetary atmospheres and oceans, their weather and climate, and the motions of 'the solid Earth'.

In this session we invite contributions expanding our understanding of the complex behavior of geophysical flows and Turbulence, presenting novel techniques that either facilitate a deeper understanding or improve the efficiency of numerical procedures involved, and/or reviewing major advances in a particular aspect of geophysical fluid dynamics. In these contexts, the role of waves (non-linear, inertial, internal, vorticity or helicity waves), turbulence and transport are an important factor in the understanding of GFD flows.

The interdisciplinary character of dynamical and computational aspects of this session encourages an exchange of ideas and contributions across various fields, such as meteorology, oceanography, astrophysics, geological fluid dynamics, applied mathematics, and computational fluid dynamics with applications to ocean and atmosphere and their Biological influences.
The recent improvements in Remote Sensing of the Earth and other Planets also allows comparison with Laboratory and Numerical Experiments involving Stratification, Rotation, Magnetic Fields, body forces, etc... Other NP6.x sessions address complementary aspects affecting Geo-Astrophysical Turbulence.

Tides form a unique process in the Earth system because of their predictability, and because of their impact on many Earth system processes. This session is open to any aspect of tidal research, including the accuracy of present-day coastal, regional and global tide models, tidal dissipation, and the role of tides in geophysics, internal tides and their role in mixing the ocean and the impact on the global ocean circulation, secular and long-term changes in tides, insights on tidal variability from global geodetic observing techniques, and new techniques for measuring tides and analysing the data. We also welcome new findings on Earth and atmospheric tides, the role of tides in Earth’s ability to host and evolve life, tides in lakes, and planetary tides. The session is also intended to mark the 100th anniversary of the founding of the Liverpool Tidal Institute (LTI). The LTI for many years was the world centre for knowledge of the tides, with Joseph Proudman taking the lead in dynamical theories, and Arthur Doodson in the analysis of tidal information from around the world, and on tidal prediction. We therefore also welcome presentations on the history of tidal research.

The variability of the stratosphere plays a key role for many atmospheric phenomena. Examples include the dynamical two-way coupling between the stratosphere and troposphere during sudden stratospheric warming events, the transport of trace gases through the meridional circulation of the stratosphere, or the connection between the Quasi-Biennial Oscillation of the tropical stratosphere and the Madden-Julian Oscillation. This session is interested in all aspects of stratospheric circulation variability, including the mechanisms behind the vertical coupling between the stratosphere and troposphere in tropics and extratropics, the importance of stratospheric dynamics for explaining both short-term atmospheric weather and long-term climate variability, and the role of the stratospheric circulation for the chemical composition of the atmosphere. We welcome abstracts that study this problem from an observational, modelling, or theoretical viewpoint on all temporal and spatial scales.

In many respects internal gravity waves (IGWs) still pose major questions both to the atmospheric and ocean sciences, and to stellar physics. Important issues are IGW radiation from their various relevant sources, IGW reflection at boundaries, their propagation through and interaction with a larger-scale flow, wave-induced mean flow, wave-wave interactions in general, wave breaking and its implications for mixing, and the parameterization of these processes in models not explicitly resolving IGWs. Also the observational record, both on a global scale and with respect to local small-scale processes, is not yet sufficiently able to yield appropriate constraints. The session is intended to bring together experts from all fields of geophysical and astrophysical fluid dynamics working on related problems. Presentations on theoretical, modelling, experimental, and observational work with regard to all aspects of IGWs are most welcome.

Invited speakers: Early career scientist Claudia Stephan (MPI), and Louis Gostiaux (CNRS / École Centrale de Lyon).

The infrasound field, the science of low-frequency acoustic waves, has developed into a broad interdisciplinary field encompassing academic disciplines of geophysics and recent technical and scientific developments. The infrasound network of the International Monitoring Network (IMS) for nuclear test ban verification and regional cluster arrays deployed around the globe have demonstrated their capacity for detecting and locating most of the disturbances in the atmosphere. Infrasound is capable of traveling up to thermospheric altitudes and over enormous ranges, where its propagation is controlled by the wind and temperature structure. Recent studies point out new insights on quantitative relationships between observables and atmospheric characteristics, and therefore opening a new field for atmospheric remote sensing.

New studies using lidar, radar, microwave spectrometer and mesospheric airglow observations complemented by satellite measurements help to better determine the interaction between atmospheric layers from the ground to the mesosphere and the influence of atmospheric waves on the mean flow. It is expected that further developing multi-instruments platforms would improve gravity wave parameterizations and enlarge the science community interested by operational infrasound monitoring. The ARISE project, funded by the European Commission, coordinates such studies. It proposes to design a novel infrastructure that integrates different atmospheric observation networks to infer a new 3D image of the atmosphere from the ground to mesosphere. In a higher frequency range, this monitoring system also offers a unique opportunity to provide in near-real time continuous relevant information about natural hazards with high societal benefits, like large volcanic eruptions, surface earthquakes or meteorites.

We invite contributions on current studies on sensors, characterization of different sources and large scale atmospheric phenomena, characterization of phenomena which affect acoustic propagation, utilization of acoustic waves to probe the atmosphere, contribution of gravity and planetary waves to the atmospheric dynamics and the coupling of atmospheric layers. In the session, we will also consider the role that infrasound and acoustic-gravity waves play in the coupled Earth’s crust – ocean – atmosphere system and, in particular, in ionospheric manifestations of physical processes in the ocean and in the solid Earth.

This session deals with atmospheric convection, being dry, shallow, or deep convection. Contributions on these aspects resulting from the use of large-eddy simulations, convection-permitting simulations, coarser-resolution simulations using parameterised convection and observations are welcome. Particular topics of interest include:

-process studies on the lifecycle of convection
-factors controlling the organisation / self-aggregation of convection and its importance for climate
-interactions of convection with other physical processes, e.g. related to the land surface, radiation
-interactions of convection with the large-scale circulation
-bias in the representation of convection in numerical weather prediction and climate models
-development of cumulus parameterisation
-impact of convection on predictability
-chemistry and chemical transport in convection

This session explores advances and challenges in convection-permitting atmospheric modelling: using the newest generation of atmospheric models that allow for the explicit treatment of convective processes (grid spacing ≤ 4 km).

Convection-permitting models (CPMs) are a rapidly growing area of research and have been shown to improve both the diurnal convective cycle and the representation of convective precipitation, particularly extremes. Furthermore, CPMs often exhibit important differences in feedback mechanisms and climate change signals compared to models with parametrized deep convection. CPMs offer a promising tool to better understand fine-scale processes and provide critical information to stakeholders, especially in areas affected by convective extremes and mountainous regions, and have thus sparked wider interest in their applications and development. For example, the CORDEX Flagship Pilot Study (FPS) on convective phenomena over Europe and the Mediterranean.

The session brings together numerical modellers, the observational community, cloud physicists, forecasters and CORDEX-FPS participants, with the aim of advancing understanding of convection and high-resolution modelling in general (including convective storm life cycle and convective organization) with new modelling and statistical observation approaches. Contributions on new high-resolution/sub-daily observational datasets, and their application to CPM evaluation, are particularly welcome. This session calls for papers on state-of-the-art development and application of CPM activities, including examination of interactions between convection and other atmospheric phenomena (e.g. boundary layers, cloud physics, radiation), as well as CPM investigations of local- to regional-scale phenomena (e.g. land-use change, land-ocean contrasts, flow-orography interactions, urban-rural transitions, aerosol effects, etc.). We welcome studies of past, present or future climates, and CPM modelling across time scales. Particular attention is given to extremes.

Other topics include, but are not limited to:
-- Model setup and parametrization, including sensitivity to resolution and dynamics
-- Model evaluation and new evaluation metrics/methods
-- Ensemble-based approaches to quantify predictability/uncertainty at convective scale
-- Physical understanding of the added value compared to coarser models
-- Land-atmosphere coupling at convection-permitting scale
-- Application to climate studies
-- Tropical phenomena
-- Convection, energy balance and hydrological cycle
-- Lightning in CPMs
-- Teleconnection across scales
-- Novel high-resolution experiments

The session will include a solicited talk from Christoph Schär (ETH Zürich) on prospects and challenges in convection-resolving modelling. The session will be chaired by M Tölle and H Truhetz.

Lightning is the energetic manifestation of electrical breakdown, occurring after charge separation processes operating on micro and macro-scales, leading to strong electric fields within thunderstorms. Lightning is associated with severe weather, torrential rains and flash floods. It has significant effects on various atmospheric layers and drives the fair-weather electric field. It is a strong indicator of convective processes on regional and global scales, potentially associated with climate change. Thunderstorms and lightning are also associated to the production of energetic radiation up to tens of MeV on time scales from sub-millisecond (Terrestrial Gamma-ray Flashes) to tens of seconds (gamma-ray glows).

This session seeks contributions from research in atmospheric electricity on:

Atmospheric electricity in fair weather and the global electrical circuit
Atmospheric chemical effects of lightning and LtNOx
Middle atmospheric Transient Luminous Events
Energetic radiation from thunderstorms and lightning.
Remote sensing of lightning from space and by lightning detection networks
Results from the Atmosphere-Space Interaction Monitor (ASIM) mission.
Thunderstorms, flash floods and severe weather
Lightning and climate
Modeling of thunderstorms and lightning
Now-casting and forecasting of thunderstorms
New airborne and ground-based observation techniques

Extreme convective events are increasing in northern and eastern Europe in frequency and intensity causing many deaths, injuries and damage to property every year, and accounting for major economic damages related to natural disasters in several countries. Atlantic hurricanes become extra-tropical cyclones and, sometimes, reach northern Europe. Mediterranean hurricanes (Medicanes or tropical-like cyclones) are not that frequent as other convective systems or tropical cyclones, but these can still reach the intensity of tropical cyclones, causing severe damages in the Southern European region. Supercells and connected tornadoes are also becoming more frequent in central Europe.

In recent years, attention was paid to the detection and monitoring of volcanic ash clouds as their impact on the European air traffic control system was unprecedented. In 2010 the Eyjafjallajökull eruption caused the closure of the airspace of several countries generating the largest air traffic shutdown since the World War II. Volcanic clouds are very dangerous for the aviation operations as they can cause damage of the aircraft systems and engines not only close to active volcanoes but also at large distance from the eruption, and they affect economic, political and cultural activities. Europe is located between the chain of Icelandic and Italian/African volcanoes which are unpredictable, and could easily emanate the ash clouds throughout the skies of the continent.

The recent Anak Krakatau eruption (December 2018) highlighted the issue on different techniques to distinguish volcanic ash clouds than convective clouds and the unsolved problem to understand if the cloud top was tropospheric or stratospheric. Specific discussion on this topic will be very welcome to the session.

The extreme convective clouds and the volcanic ash clouds are types of “extreme clouds”. The “extreme clouds” detection and estimation of their physical parameters is a highly multidisciplinary and challenging topic since the same techniques and instruments can be used for meteorology, volcanic monitoring, atmospheric physics and climate purposes. But there is an urgent need to develop new techniques and instruments for monitoring, detecting and modeling “extreme clouds” to develop early warning systems and to support users, decision makers and policy makers. Given the large uncertainties that still remain in the field, enlarging and coordinating the research community for developing new techniques and improving our knowledge is required. Furthermore, there is a need for improved information exchange regarding the impact of the extreme clouds on daily operations between the producers and intended uses of the information.

The objective of the session is to connect different communities in touch with the “extreme clouds”, such as scientists working in remote sensing, modelers, meteorologists, physicists, aviation managers. Thus, allowing the researchers to understand the end-users’ needs and for the end-users to understand the research capabilities.

This session solicits the latest studies from the spectrum of:
- detection, monitoring and modeling of extreme clouds,
- understanding the impact of extreme clouds on climate changes,
- proposal of new products or services focused on the end-users prospective,
- discussion on Anak Krakatau eruption (December 2018)

By considering studies over this range of topics we aim to identify new methods, detail current challenges, understand common techniques/methods and identify common discussions within the communities of atmospheric physicists, meteorologists, modelers, air traffic managers, pilots sensors engineers and engines manufacturers. We particularly welcome and encourage contributions connecting different fields such as:
- forecasting tools to support air traffic management improving the limits of the present science and new products/tools providing better services to the end-users,
- extreme clouds remote sensing with novel techniques and new sensors,
- novel techniques to detect overshooting and their impact on climate.

The aim of the session is to promote discussions between scientists on future developments, in understanding, monitoring and forecasting the extreme clouds, studying their impact and to extend the discussion with the end-users for improving air safety. This session is thus open to contributions on all aspects of remote sensing, forecast, and tools/services development such as:

- Extreme clouds remote sensing
- Extreme clouds modeling
- Extreme clouds forecasting and nowcasting
- Extreme clouds structure
- Extreme clouds and climate change
- Overshooting and Ice clouds
- Air traffic management issues related to extreme clouds
- Airport issues

Precipitation, both liquid and solid, is a central element of the global water/energy cycle through its coupling with clouds, water vapor, atmospheric motions, ocean circulation, and land surface processes. Precipitation is also the primary source of freshwater, while it can have tremendous socio-economical impacts associated with extreme weather events such as hurricanes, floods, droughts, and landslides. Accurate and timely knowledge of precipitation characteristics at regional and global scales is essential for understanding how the Earth system operates under changing climatic conditions and for improved societal applications that range from numerical weather prediction to freshwater resource management. This session will host papers on all aspects of precipitation, especially contributions in the following four research areas: Precipitation Measurement: Precipitation measurements (amount, duration, intensity etc) by ground-based in situ sensors (e.g., rain gauges, disdrometers); estimation of accuracy of measurements, comparison of instrumentation. Precipitation Climatology: Regional and global climatology; areal distribution of measured precipitation; classification of precipitation patterns; spatial and temporal characteristics of precipitation; methodologies adopted and their uncertainties; comparative studies. Precipitation Remote Sensing: Remote sensing of precipitation (spaceborne, airborne, ground-based, underwater, or shipborne sensors); methodologies to estimate areal precipitation (interpolation, downscaling, combination of measurements and/or estimates of precipitation); methodologies used for the estimation (e.g., QPE), validation, and assessment of error and uncertainty of precipitation as estimated by remote sensors. A special focus will be on international contributions to the exploitation of the international Global Precipitation Measurement (GPM) mission that provides state-of-the-art precipitation estimates (including solid precipitation) from space with unprecedented accuracy, time-space coverage, and improved information for microphysics. Precipitation Modeling: Quantitative precipitation forecasts from numerical weather prediction models including ensemble forecast of precipitation and probabilistic approaches; verification of precipitation forecasts using different techniques (e.g., gridded and object oriented); precipitation nowcasting with assimilation of radar and satellite data; understanding precipitation processes including microphysics for model improvements.

The assessment of precipitation variability and uncertainty is crucial in a variety of applications, such as flood risk forecasting, water resource assessments, evaluation of the hydrological impacts of climate change, determination of design floods, and hydrological modelling in general. Within this framework, this session aims to gather contributions on research, advanced applications, and future needs in the understanding and modelling of precipitation variability, and its sources of uncertainty.
Specifically, contributions focusing on one or more of the following issues are particularly welcome:
- Novel studies aimed at the assessment and representation of different sources of uncertainty versus natural variability of precipitation.
- Methods to account for different accuracy in precipitation time series, e.g. due to change and improvement of observation networks.
- Uncertainty and variability in spatially and temporally heterogeneous multi-source precipitation products.
- Estimation of precipitation variability and uncertainty at ungauged sites.
- Precipitation data assimilation.
- Process conceptualization and modelling approaches at different spatial and temporal scales, including model parameter identification and calibration, and sensitivity analyses to parameterization and scales of process representation.
- Modelling approaches based on ensemble simulations and methods for synthetic representation of precipitation variability and uncertainty.
- Scaling and scale invariance properties of precipitation fields in space and/or in time.
- Physically and statistically based approaches to downscale information from meteorological and climate models to spatial and temporal scales useful for hydrological modelling and applications.

The global monsoon system and its regional monsoon components have profound impacts on society and are among the most complex phenomena involving coupled atmosphere-ocean-land interactions. Monsoons can cause severe floods and droughts in the tropics and some parts of the subtropics as well as undergoing climate variability on subseasonal, interannual and decadal to centennial (or longer) time scales. In addition to its profound local effects, monsoon variability is also associated with global-scale impacts since the energy released by monsoon systems can influence the global circulation. However, it is notoriously difficult to simulate and forecast the monsoons at all temporal scales, in numerical weather prediction (NWP), subseasonal-to-seasonal and interannual-to-decadal predictions, and centennial-to-longer timescale projections. A better understanding of monsoon physics and dynamics, with more accurate simulation, prediction and projection of monsoon systems is therefore of a great practical importance to the atmospheric sciences community and society.

The combination of modern- and palaeo-monsoon research can help us to better understand the fundamental nature of the monsoon and its variability. Comparisons of monsoon responses to large-scale forcings found in the palaeoclimate record can help us to understand how the monsoon will respond to changes in forcings in the future, potentially allowing us to constrain estimates of climate change. Similarly, the wealth of observations, reanalysis products and modelling work in the contemporary period can help us piece together data from point-proxy records of the past.

This session therefore invites presentations on all aspects of monsoon research in contemporary, future and palaeoclimate periods (observational, modeling, attribution, prediction and projection) from the natural and anthropogenic variability and predictability of the monsoon systems on multiple time scales, to the impact of monsoons on extreme weather and climate events (floods, droughts, tropical cyclones, heat waves, etc.), as well as the links between monsoons and global climate change and feedbacks with the biosphere.

ENSO is the dominant source of interannual climate variability in the tropics and across the globe. Understanding ENSO's dynamics, predicting El Niño and La Niña, and anticipating changes in ENSO's characteristics and impacts are thus of vital importance for society. This session invites contributions regarding the dynamics of ENSO, including multi-scale interactions; low frequency, decadal and paleo ENSO variability; ENSO theory; ENSO diversity; ENSO impacts on climate, society and ecosystems; ENSO teleconnections; seasonal forecasting of ENSO; and climate change projections of ENSO. Studies aimed at understanding ENSO in models of a range of complexity are especially welcomed, including analysis of CMIP model intercomparisons.

The seasonal reversal of monsoon winds and concurrent ocean currents, relatively deep thermocline along the equator due to the lack of steady easterlies, low-latitude connection to the neighboring Pacific and a lack of northward heat export due to the position of the Asian continent make the Indian Ocean unique among the other tropical ocean basins. These characteristics shape the Indian Ocean’s very dynamic intraseasonal, seasonal, and interannual variability, as well as its air-sea interactions. They also make the basin and its surrounding regions, which are home to a third of the global population, particularly vulnerable to anthropogenic climate change, and robust warming and trends in heat and freshwater fluxes have been observed in recent decades. Advances have recently been made in our understanding of the Indian Ocean’s circulation, interactions with adjacent ocean basins, and its role in regional and global climate. Nonetheless, significant gaps remain in understanding, observing, modeling, and predicting Indian Ocean variability and change across a range of timescales.

This session invites contributions based on observations, modelling, theory, and palaeo proxy reconstructions in the Indian Ocean that focus on understanding and predicting the links between Indian Ocean variability and monsoon systems on (intra)seasonal to interannual timescales, interactions and exchanges between the Indian Ocean and other ocean basins, decadal variability and its prediction, response to climate change, extreme events, as well as interactions between physical, biogeochemical, and ecological processes. Contributions are also sought that address research on the Indian Ocean grand challenges, as formulated by the Climate and Ocean: Variability, Predictability, and Change (CLIVAR), the Sustained Indian Ocean Biogeochemistry and Ecosystem Research (SIBER), and the International Indian Ocean Expedition 2 (IIOE-2) programs.

Observations and simulations of ocean circulation and marine atmosphere processes are rapidly growing for meso to basin scale, on diurnal to interannual scale. This session focuses on tropical and subtropical ocean dynamics as well as local interaction between the ocean and the overlying atmosphere from the equator to mid-latitudes. Relevant processes in the ocean include upper and deep ocean circulation variability, mild SST gradients to sharp fronts, eddies, filaments, tropical instability waves, warm pools, upper ocean various layers, cold tongues and eastern boundary upwelling. Regarding air-sea interactions, we seek studies that analyse the local to regional scales, and those discussing the conditions under which they may lead to a large-scale atmospheric response. Surface wind modulations, Madden-Julian Oscillation, cyclones, and convective systems, as well as scale interactions are welcome. In the extra-tropics, we seek also contributions on the role of extra-tropical fronts in regional and large-scale atmospheric circulation. We welcome contributions on how the air-sea interactions may shape modes of climate variability and determine regional climate sensitivity.

The understanding of tropical phenomena and their representation in numerical models still raise important scientific and technical questions, particularly in the coupling between the dynamics and diabatic processes. Among these phenomena, tropical cyclones (TC) are of critical interest because of their societal impacts and because of uncertainties in how their characteristics (cyclogenesis processes, occurrence, intensity, latitudinal extension, translation speed) will change in the framework of global climate change. The monitoring of TCs, their forecasts at short to medium ranges, and the prediction of TC activity at extended range (15-30 days) and seasonal range are also of great societal interest.

The aim of the session is to promote discussions between scientists focusing on the physics and dynamics of tropical phenomena. This session is thus open to contributions on all aspects of tropical meteorology between the convective and planetary scale, such as:

- Tropical cyclones,
- Convective organisation,
- Diurnal variations,
- Local circulations (i.e. island, see-breeze, etc.),
- Monsoon depressions,
- Equatorial waves and other synoptic waves (African easterly waves, etc.),
- The Madden-Julian oscillation,
- etc.

We especially encourage contributions of observational analyses and modelling studies of tropical cyclones and other synoptic-scale tropical disturbances including the physics and dynamics of their formation, structure, and intensity, and mechanisms of variability of these disturbances on intraseasonal to interannual and climate time scales.

Findings from recent field campaigns such as YMC and PISTON are also encouraged.

Clouds are a key component of the climate system, and the numerical models we use to predict future climate change do not reproduce them well. Our inability to simulate clouds stems from a poor process-level understanding, and there is a large community of scientists focusing on using high resolution models to understand clouds on a microphysical scale.

This session aims to showcase the latest advances in cloud modelling, providing a forum for discussions between scientists using various cloud process modelling techniques. Submissions using bin or bulk microphysics schemes, modelling clouds from stratocumulus to cumulonimbus, are encouraged.

In this session, we welcome submissions concerning:
Improved process understanding from high resolution modelling
New parameterisation developments (e.g. regarding INP/CCN, autoconversion or process rates)
Mixed-phase cloud modelling (e.g. phase partitioning, precipitation production)
Secondary ice production
New cloud models
Aerosol-cloud interactions from local aerosol sources
Importance of dynamical interactions (e.g. entrainment, large-scale meteorology)
Simulations of cloud phenomena requiring high resolution (e.g. cold-air outbreaks)

Submissions from Early Career Researchers are encouraged, and we will reserve oral presentation slots for such abstracts.

Clouds and aerosols play a key role in climate and weather-related processes over a wide range of spatial and temporal scales. An initial forcing due to changes in the aerosol concentration and composition may also be enhanced or dampened by feedback processes such as modified cloud dynamics, surface exchange or atmospheric circulation patterns. This session aims to link research activities in observations and modelling of radiative, dynamical and microphysical processes of clouds and aerosols and their interactions. Studies addressing several aspects of the aerosol-cloud-radiation-precipitation system are encouraged.

Topic covered in this session include:
- Cloud and aerosol macro- and microphysical properties, precipitation formation mechanisms
- The role of aerosols and clouds for the radiative energy budget
- Observational constraints on aerosol-cloud interactions
- Cloud-resolving modelling
- Parameterization of cloud and aerosol microphysics/dynamics/radiation
- Use of observational simulators to constrain aerosols and clouds in models
- Experimental cloud and aerosol studies
- Aerosol, cloud and radiation interactions and feedbacks in the climate system

Invited Speaker
Paquita Zuidema (RSMAS, University of Miami)
Leo Donner (NOAA GFDL)

The southeast Atlantic off the African south western coast is the location for interactions between aerosols, clouds, and radiation ultimately affecting climate. A wide-spread stratocumulus cloud deck is a permanent feature in this region shaping the regional radiation budget, the local water budget through the formation of coastal fog, and potentially the global climate. Aerosols from multiple sources, including biomass and fuel burning, mineral dust, and marine, emitted or transported below or above the cloud deck, can significantly change the microphysical and radiative properties of the clouds. Currently these processes are poorly understood, which is reflected in the diversity of model simulation results of radiative forcing. Studies that present new observations and modelling of the aforementioned properties, interactions and implications over the southeast Atlantic and adjacent continental regions are solicited

The session is addressed to experimentalists and modellers working on land surface fluxes from local to regional scales. The programme is open to a wide range of new studies in micrometeorology. The topics include the development of new devices, measurement techniques and experimental design methods, as well as novel findings on surface layer theory and parametrization at the local scale. The theoretical parts encompass soil-vegetation-atmosphere transport, internal boundary-layer theories and flux footprint analyses, etc.. Of special interest are comparisons of experimental data, parametrizations and models. This includes energy and trace gas fluxes (inert and reactive) as well as water, carbon dioxide and other GHG fluxes. Specific focus is given to outstanding problems in land surface boundary layer descriptions such as complex terrain, energy balance closure, stable stratification and night time fluxes, as well as to the dynamic interactions with atmosphere, plants (in canopy and above canopy) and soils including the scale problems in atmosphere and soil exchange processes.

Driven by atmospheric turbulence, and integrating surface processes to free atmospheric conditions, the Atmospheric Boundary Layer (ABL) plays a key role not only in weather and climate, but also in air quality and wind/solar energy. It is in this context that this session invites theoretical, numerical and observational studies ranging from fundamental aspects of atmospheric turbulence, to parameterizations of the boundary layer, and to renewable energy or air pollution applications. Below we propose a list of the topics included:

- Observational methods in the Atmospheric Boundary Layer
- Simulation and modelling of ABL: from turbulence to boundary layer schemes
- Stable Boundary Layers, gravity waves and intermittency
- Evening and morning transitions of the ABL
- Convective processes in the ABL
- Boundary Layer Clouds and turbulence-fog interactions
- Micro-Mesoscale interactions
- Micrometeorology in complex terrain
- Agricultural and Forest processes in the ABL
- Diffusion and transport of constituents in the ABL
- Turbulence and Air Quality applications
- Turbulence and Wind Energy applications

Solicited talk:

- "Revisiting Monin-Okukhov Similarity Theory",
by Jielun Sun, NorthWest Research Associates, Boulder, Colorado, USA.

Changes in the Arctic and Antarctic climate systems are strongly related to processes in the boundary layer and their feedbacks with the free troposphere. An adequate understanding and quantification of these processes is necessary to improve predictions of future changes in the polar regions and their teleconnections with mid-latitude weather and climate, including meridional transport of heat, moisture and air pollutants. Processes include atmosphere-ocean-ice (AOI) interactions, such as physical and chemical snow processes (e.g. snow photochemistry), exchange of chemical constituents, sources of aerosol, polynya formation processes, sea ice production and bottom water formation, and cloud formation, which represent key processes for the atmosphere, ocean and the cryosphere. AOI interactions are also triggered by and have feedbacks with synoptic systems and mesoscale weather phenomena such as cold air outbreaks, katabatic winds and polar lows. Associated processes also include the effect of warm air advection and clouds on the surface energy budget and related boundary layer exchanges. Of increasing interest is the study of extremes such as heat waves and storms, but also extreme meridional transport events that can disturb the physical and chemical state of the high latitudes and may have a large impact on ecosystem changes. In addition, Arctic boundary-layer processes play an important role for local Arctic air pollution and for the health and ecosystem impacts thereof. In addition, understanding natural processes including AOI interactions is essential to understand of the background atmosphere to quantify the anthropogenic impacts. Shallow inversions, mostly during winter-time, lead to high air pollutant concentrations. Even though severe air pollution episodes are frequently observed in the Arctic, knowledge on urban emission sources and atmospheric chemical processing of pollution, especially under cold and dark conditions, are poorly understood.

This session is intended to provide an interdisciplinary forum to bring together researchers working in the area of boundary layer processes and high-latitude weather and climate (including snow physics, air/snow chemistry, and oceanography). Cryosphere and atmospheric chemistry processes (the focus of the IGAC/SOLAS activity “CATCH” and the IGAC/IASC activity “PACES”) are highly relevant to this session. We invite contributions e.g. in the following areas:

1. Observations and research on the energy balance, physical and chemical exchange processes, and atmosphere-ocean-ice (AOI) interactions including particle sources.
2. Results from high-elevation sites where similar processes occur over snow and ice.
3. Field programs, laboratory studies and observational studies (including remote sensing).
4. Model studies and reanalyses.
5. Advances in observing technology.
6. External controls on the boundary layer such as clouds, aerosols, radiation.
7. Teleconnections between the polar regions and mid-latitudes resulting in effects related to atmosphere-ice-ocean interactions as well as insights provided by monitoring of water vapor isotopes that shed light on air mass origins.
8. High-latitude urban air quality studies.

Physical processes of Air-Sea Interaction and their representation

This session aims at fostering exchanges and discussions on the physical processes at work at the air-sea interface, their observation, and their representation in coupled numerical models.

Examples of such processes are sun-induced diurnal warming and rain-induced cool and fresh lenses, as well as gustiness associated with atmospheric boundary layer thermals or moist convection and cold pools induced by rain evaporation. Surface temperature and salinity fronts, oceanic meso- and sub-mesoscale dynamics are also of great interest.

This session is thus intended for (i) contributions presenting observational or theoretical aspects of the processes described above and their impact on energy and water exchanges at the interface, and (ii) contributions focusing on the mathematical and algorithmic methods used to represent these processes in coupled ocean-atmosphere models.

This session seeks observational studies based on recent campaigns such as (but not limited to) SPURS-2, YMC, or PISTON, or on satellite remote sensing. This session also aims to gather studies using numerical models of any level of complexity (from highly idealized to realistic) and any resolution from Large Eddy Simulation (LES) to global circulation models. Studies describing the impact of the air-sea interaction physical processes on the mean global or regional climates and variability representation are also welcome.

We invite presentations on ocean surface waves: their dynamics, modelling and applications. Wind-generated waves are a large topic of the physical oceanography in its own right, but it is also becoming clear that many large-scale geophysical processes are essentially coupled with the surface waves, and those include climate, weather, tropical cyclones, Marginal Ice Zone and other phenomena in the atmosphere and many issues of the upper-ocean mixing below the interface. This is a rapidly developing area of research and geophysical applications, and contributions on wave-coupled effects in the lower atmosphere and upper ocean are strongly encouraged.

The multitude of processes of various scales occurring simultaneously under strong winds in the air and sea boundary layers presents a true challenge for nonlinear science. We want to understand the physics of these processes, their specific role, their interactions and how they can be probed remotely, how these processes differ from their counterparts under moderate/weak winds. We welcome theoretical, experimental and numerical works on all aspects of processes in turbulent boundary layers above and below the ocean surface. Although we are particularly interested in the processes and phenomena occurring under strong wind conditions, the works concerned with similar processes under weaker winds which might provide an insight for rough seas are also welcomed. We are also very interested in works on remote sensing of these processes.
The areas of interest include the processes at and in the vicinity of the interface (nonlinear dynamics of surface water, wave-current-turbulence interactions, , including wave and current stability, wave breaking, generation and dynamics of spray and air bubbles, thermodynamics of the processes in the boundary layers, heat and gas exchange), all the processes above and below the air/water interface, as long as they are relevant for strong wind conditions (such as, e.g. inertial waves generated by changing winds). Relevant nonlinear biological phenomena are also welcomed.

The main aims of the session is to initiate discussion of the multitude of processes active under strong winds across the narrow specializations as a step towards creating an integrated picture. Theoretical, numerical, experimental and observational works are welcomed.

The energy of a closed system is steady. It is not lost but rather converted into other forms, such as when kinetic energy is transferred into thermal energy. However, this fundamental principle of natural science is often still a problem for climate research. For example, in case of the calculation of ocean currents and circulation, where small-scale vortices as well as diapycnal mixing and the deep convection processes they induce, need to be considered, to compute how heat content is redistributed along the entire water column and how such processes may change in the future. Similarly, in the atmosphere, the conversion of available potential energy into kinetic energy is the key driver of atmospheric dynamics at a variety of scales, from the zonal-mean general circulation to mesoscale convection. Local turbulent processes can drive larger movements and waves on a larger scale can disintegrate into small structures. All these processes are important for the Earth’s climate and determine its evolution in the future.

How exactly the energy transfers between waves, eddies, local turbulence and mixing in the ocean and the atmosphere works, often remains unclear. This session wants to discuss this by inviting contributions from oceanographers, meteorologists, climate modelers, and mathematicians. We are particularly interested in coupled atmosphere-ocean studies, we are also aiming at filling a knowledge gap on deep ocean processes, as well as novel subgrid-scale parameterizations, and studies of the energy budget of the complex Earth system, including the predictability of the global oceanic thermohaline circulation and thus climate variability.

Invited speakers:
Martin Wild, ETH, Zürich, Switzerland
Raffaele Ferrari, MIT, USA
Robert Weller, WHOI and OOI Research Infrastructures, USA

Aerosol particles are key components of the earth system important in radiative balance, human health, and other areas of key societal concern. Understanding their formation, evolution and impacts relies on developments from multiple disciplines covering both experimental laboratory work, field studies and numerical modelling. In this general session all topics of Aerosol Chemistry and Physics are covered. Contributions from aerosol laboratory, field, remote sensing and model studies are all highly encouraged.

As in previous years, this year the session will dedicate some of its time to focus on a hot topic which this year is aerosol volatility. Despite significant advances in experimental techniques, it is still thought that an incomplete understanding of factors that dictate gas-particle partitioning remains one of the major uncertainties in predicting atmospheric aerosol concentrations, composition, life-time and subsequent impacts. With this in mind, aside from general submissions on aerosol research, we encourage contributions from work within the broad focus of aerosol volatility. These might include work on:
• New process pathway identification
• Molecular scale investigations, from single component to complex mixtures
• Evidence from field studies
• New experimental capabilities
• New modelling capabilities
• Impact studies

Atmospheric aerosol-cloud-climate interactions (e.g. particle oxidation and photosensitization, secondary aerosol and biogenic particle formation, molecular composition-, phase-, acidity- and structure- changes, heterogeneous ice nucleation ...) are fundamental processes in the atmosphere. Despite the importance of these processes in energy transfer, cloud dynamics, precipitation formation, and hence in climate change, little is known about the molecular mechanism and the respective contribution of different structural and chemical surface properties of the atmospheric aerosols and ice nuclei controlling these processes in the atmosphere. For example, observation of atmospheric ice nucleation has bridged the scales from macroscopic to microscopic levels (satellites, balloons, mountain stations, flight campaigns, and laboratory measurements) and has delivered a wide variety of important results in cloud microphysics, particularly concerning the ice nucleation ability of atmospheric aerosol particles. However, fundamental understanding of the cloud dynamics and properties, which play the major role in the climate system, will require the understanding of water-aerosol Surface Interactions.

To advance our knowledge about atmospheric processes, this session aims to bring together experimental and theoretical approaches concerned with investigating water- and ice-solid interactions as well as ice nucleation processes on the molecular level. The goal is to fill the gap between the cloud and atmospheric properties and the aerosol-water surface interactions. We aim to gather contributions from laboratory and theoretical investigations that deal with the interaction of water and ice with atmospheric relevant mineral and biological surfaces.

- Invited speaker: Prof. Dr. Mischa Bonn, Max Planck Institute for Polymer Research, Mainz , Germany.
- Solicited talk: "Hydrogen Bonding at the Ice Surface"

- Most exciting for non-scientific public talk: "Elucidating how trace gases interact with ice surfaces", by Dr. Jenée D. Cyran

Public information:
In the “Atmospheric Surface Science” session we bridge experimental and theoretical findings to elucidate water-ice-aerosol interactions that occur in the atmosphere. The focus is on the molecular level processes. We discuss the origin of the interactions and their impact on our hydrosphere in general and climate in particular.

Ice particles in the atmosphere, both in cirrus and mixed-phase clouds, contribute to the largest uncertainty in interpretations of the Earth’s changing energy budget. Their large variability in number, size and shape makes it difficult to understand and parameterize their microphysical and hence radiative properties.

To advance our understanding of these clouds, this session aims to bring together two research areas, namely (1) 'Ice Clouds (IC)' and (2) 'Ice Nucleating Particles (INP)':

(1) 'Ice Clouds (IC)' are investigated with different approaches and methodologies: observations (ground based, airborne and spaceborne), modelling (process-based, regional and global) as well as radiative transfer and transport studies. We aim to gather contributions from all these aspects including dynamical influence on ice cloud formation, life cycle, coverage, microphysical and radiative properties, crystal shapes, sizes and variability of ice particles for mixed-phase as well as cirrus clouds.

(2) 'Ice Nucleating Particles (INP)' are examined in the laboratory on a fundamental level, trying to understand the nucleation processes. For characterizing INP in the atmosphere, their temperature dependent number concentrations are determined by ground based and aircraft measurements, and also remote sensing.

This session is intended to promote the exchange of knowledge between the different communities, and welcomes contributions from all topics mentioned above.

Just before the EGU, from 3rd to 6th April 2019, the Viennese colleagues Bernadett Weinzierl, Anne Kasper-Giebl and Hinrich Grothe will organize the 12th International Conference on Carbonaceous Particles in the Atmosphere (ICCPA) 2019, where ice nucleation will also be a highlighted topic: www.iccpa.net

Atmosphere and Cryosphere are closely linked and need to be investigated as an interdisciplinary subject. Most of the cryospheric areas have undergone severe changes in last decades while such areas have been more fragile and less adaptable to global climate changes. This AS-CR session invites model- and observational-based investigations on any aspects of linkages between atmospheric processes and snow and ice on local, regional and global scales. Emphasis is given on the Arctic, high latitudes and altitudes, mountains, sea ice, Antarctic regions. In particular, we encourage studies that address aerosols (such as Black Carbon, Organic Carbon, dust, volcanic ash, diatoms, bioaerosols, bacteria, etc.) and changes in the cryosphere, e.g., effects on snow/ice melt and albedo. The session also focus on dust transport, aeolian deposition, and volcanic dust, including health, environmental or climate impacts at high latitudes, high altitudes and cold Polar Regions. We emphasize contributions on biological and ecological sciences including dust-organisms interactions, cryoconites, bio-albedo, eco-physiological, biogeochemical and genomic studies. Related topics are light absorbing impurities, cold deserts, dust storms, long-range transport, glaciers darkening, polar ecology, and more. The scientific understanding of the AS-CR interaction needs to be addressed better and linked to the global climate predictions scenarios.

Aeolian processes operate at a myriad of spatial and temporal scales both on Earth and other planetary bodies. Process and form are linked by feedback mechanisms that drive the evolution of forms and at the larger scale the landscape itself. This session brings together research traversing the spectrum of scale, from long term landscape dating and evolution modelling to small-scale process studies. It will be of interest to researchers that study wind-blown sediment (both sand and dust sized particles) and associated bedforms in a range of environments, from coastal and semi-arid regions, to hyper arid deserts and other planets. Contributions that use novel instrumentation in field or laboratory studies, remote sensing at the landscape scale, innovative numerical modelling or theoretical approaches, are encouraged, particularly those which attempt to elucidate feedback between surface properties and sediment transport.

This session is co-sponsored by the International Society for Aeolian Research (ISAR; http://www.aeolianresearch.com/). The best student presentation (oral or poster) in this session will receive two-year ISAR membership and a book prize.

This session is the result of a merger of two sessions:
Session CL4.28/AS3.6/GM10.2/SSP3.25
"Aeolian dust: initiator, player, and recorder of environmental change", and
Session AS3.7
"Atmospheric Desert Dust characterisation through Remote Sensing observations".

Together, these two sessions cover a huge range of scientific disciplines that study mineral-dust generation, transport, and deposition, as well as the many roles that mineral dust plays in environmental change.

The merger has resulted in a very nice set of interesting dusty abstracts covering huge ranges of spatial and temporal scales and with contributions from many scientific disciplines including atmospheric science, remote sensing, (palaeo)climate science, geomorphology and sedimentology but also human health and environmental science. We look forward to an inspiring and challenging PICO session and we invite you to participate!

Public information:
We have three PICO blocks and two invited speakers (in between the 2-minute madness and PICOs):
1) Vassilis Amiridis (10.45 - 11.00) - Dust remote sensing advances in the framework of ACTRIS
2) Carlos Pérez García-Pando (14.00 - 14.15) - FRontiers in dust minerAloGical coMposition and its Effects upoN climaTe (FRAGMENT)

Remote sensing of clouds and aerosols is of central importance for studying climate system processes and changes. Reliable information is required on climate-relevant parameters such as aerosol and cloud optical thickness, layer height, particle size, liquid or ice water path and vertical particulate matter columns. A number of challenges and unsolved problems remain in algorithms and their application. This includes remote sensing of clouds and aerosols with respect to 3D effects, remote sensing of polluted and mixed clouds, combination of ground-based and satellite-based systems, and the creation of long-term uniform global records. This session is aimed at the discussion of current developments, challenges and opportunities in aerosol and cloud remote sensing using active and passive remote sensing systems.

Invited speaker 2019: Otto Hasekamp, SRON - Netherlands Institute for Space Research

Over the last years, a growing number of Multi-AXis (MAX) and other scattered light DOAS instruments is operated world wide.
By probing the troposphere in different viewing angles and from different platforms, vertical profile information on aerosols and tropospheric trace gases, in particular NO2, can be derived.
Thereby, scattered light DOAS instruments provide an essential link between in-situ measurements of trace gas concentrations and column-integrated measurements from satellite, and thus play a key role in satellite validation.
This session is open for contributions about
- MAX-DOAS and other scattered light DOAS instrumentation and operation on various platforms (ground-based, mobile, aircraft)
- trace gas retrievals
- inversion algorithms
- identification and treatment of clouds
- comparisons to in-situ or satellite measurements and models
- scientific results.
Results from intercomparison campaigns like CINDI-2 (2016 in Cabauw) are particularly welcome.

The Sentinel-5 Precursor mission, launched on Oct. 13 2017, is the first atmospheric Sentinel and will support Copernicus services in particular for atmospheric applications, including activities such as air quality, ozone and climate monitoring. The instrument TROPOMI (Tropospheric Monitoring Instrument) is the single payload of the Sentinel-5 Precursor satellite and was co-funded by ESA and The Netherlands. Sentinel-5 Precursor will ensure on the one hand continuity of atmospheric satellite data provision from the ESA ERS (GOME), ENVISAT (SCIAMACHY), and the USA EOS-AURA (OMI) missions in the various application and scientific domains and prepares on the other hand for the future atmospheric Sentinel-4 and Sentinel-5 instruments hosted on EUMETSAT platforms. Key features of the TROPOMI instrument are to have global coverage within one day and providing a spatial resolution of 7x3.5 km.
The Sentinel-5 Precursor mission has successfully finalised its Commissioning Phase on April 24 2018. During Commissioning Phase only pre-operational sample data products have been provided to selected Cal/Val experts. The staggered data release to the public has started on July 11 including Level 1B, Ozone, Nitrogen Dioxide, Carbon Monoxide and Cloud & Aerosol information. It is planned that during the ramp-up phase, which has a duration of 8 months all products will be provided to the public (by end Dec. 2018). All data will be provided to the public through the Copernicus Open Data Access Hub at https://scihub.copernicus.eu/. This session will include contributions about the Sentinel-5 Precursor mission status, calibration/validation results, and the demonstration of first applications using TROPOMI products.

Over the last years, more and more satellite data on tropospheric composition have become available and are now being used in numerous applications. In this session, we aim at bringing together reports on new or improved data products and their validation as well as studies using satellite data for applications in tropospheric chemistry, emission inversions and air quality. This includes both studies on trace gases and on aerosols.

We welcome presentations based on studies analysing current and future satellite missions, in particular Sentinel 5P, inter-comparisons of different remote sensing measurements dedicated to tropospheric chemistry sounding and/or analyses with ground-based measurements and chemical transport models.

The Middle East is home to about 350 million people. It is endowed with about half the proven oil and gas reserves on the planet, and also has rich solar resources. The Middle East also has exceptional environmental qualities, with extensive deserts, and is among the most water-scarce regions on Earth. It is subject to dust storms and heat extremes, and in some parts photochemical air pollution is unparalleled (Alizadeh-Choobari et al., 2014). Model simulations show that climate change in the Middle East is associated with particularly rapid warming in summer, and that effectively the hot desert climate is intensifying (Lelieveld et al., 2016). When the surface temperature increases over dry desert soils, relative humidity decreases, which promotes dust mobilization (Klingmuller et al., 2016). Although the Middle East is a global change hot spot, it receives relatively little attention, e.g., in reports of the Intergovernmental Panel on Climate Change (IPCC,2013). One reason is that observational data are insufficient, unavailable or of limited quality.
AQABA was a comprehensive ship borne measurement and modeling campaign of reactive gases and particles, to study the pronounced regional contrasts that occur in atmospheric pollutant and dust concentrations. It took place in summer 2017 covering a track from Toulon, France to Kuwait through the Mediterranean and around the Arabian Peninsula and back.
The session invites all relevant contributions from the region and results from the AQABA campaign will be presented.

The aim of this general session is to bring together the scientific community within air pollution modelling. The focus is ongoing research, new results and current problems related to the field of modelling the atmospheric transport and transformation on global, regional and local scales.

All presentations covering the research area of air pollution modelling are welcome, including recent model developments, applications and evaluations, physical and chemical parameterisations, process understanding, model testing, evaluation and uncertainty estimates, emissions, numerical methods, model systems and integration, forecasting, event-studies, scenarios, ensembles, assessment, etc.

This is a general open session on all aspects of gas phase chemistry. The focus of this year will be on processes affecting the oxidation capacity of the atmosphere, particularly perturbations to HOx and NOx levels in the troposphere. Field measurements, laboratory and theoretical studies which do not fit into one of the other special sessions are welcome.

Air pollution is of great concern by the public and government in Asia, specifically in India and China, due to the risk to human health. To elucidate the formation mechanisms of air pollution in Asia, numerous field studies and modelling studies have been conducted in different Asian countries in the recent years, accompanied by mandatory emission restriction strategies that have been put into action.
This session aims for presentations about recent results from field studies, and also air quality monitoring activities in Asia linked to photochemistry, aerosols, emissions of air pollutants and tropospheric chemical composition.
All stages of data analysis are welcome in this session, including presentations of early field data, modelling studies, and results on the global impact of air pollution in Asia.

Cities are hotspots for the emissions of air pollutants and greenhouse gases from traffic, industries, household heating and energy production. Air pollution impacts are episodic and often co-occur with heat waves and allergenic pollen release. Greenhouse gases are often co-emitted with air pollutants. Urban air quality and the effect of policy measures are a challenge to monitor with traditional fixed stations or with models, because of the extreme variability in the cities’ geometry and emission patterns.
This session intends to bring together researchers of urban air quality and greenhouse gases and will accept submissions of topics related to urban air quality, heat stress, and air pollution impacts including health. The presentations focus on new developments in the field of ground and satellite observations, process modelling, data merging and downscaling related to urban air quality. Topics include sensor networks, personal monitoring, observations from space and UAV’s, high spatial and temporal resolution model approaches, downscaling, source apportionment, optical properties, atmospheric processes, mechanisms for air quality deterioration, community and personal exposure quantification and air pollution effects. Air pollution species may include anthropogenic and biogenic ones, including greenhouse gases and allergenic pollen, their isotopes and concentration ratios.

The session focuses on the variability of the tropospheric and stratospheric chemical composition on diurnal, seasonal and longer timescales and looks at the processes driving this variability. Special emphasis is put on the scientific value of high-quality long-term measurement data sets and supporting model simulations. Both approaches contribute to improved understanding of the mechanisms that control the variability of atmospheric chemical composition (including multiple gaseous species). Presentations related to the projections of the atmospheric composition are welcome in this session as well.
Researchers are invited to present novel scientific results from mid- and long-term observational time series from various programmes and networks such as the Global Atmosphere Watch (GAW) Programme, European Monitoring and Evaluation Programme (EMEP), Network for the Detection of Atmospheric Composition Change (NDACC), Southern Hemisphere Additional Ozonesondes (SHADOZ), Advanced Global Atmospheric Gases Experiment (AGAGE), National Oceanic and Atmospheric Administration (NOAA), regular airborne (e.g. CARIBIC, IAGOS, CONTRAIL) and other campaigns as well as satellite data and model simulations. Data relevant to tropospheric and stratospheric composition, in particular related to ozone depletion, climate change and air quality as well as firn data on past atmospheric composition are welcome. We welcome contributions from multi-year modeling studies and inter-comparison exercises which address past and future tropospheric or stratospheric composition changes, carried out in the framework of international projects and initiatives. The session will be dedicated in particular to the celebration of the 30th anniversary of the GAW Programme.

Measurements of gaseous compounds and particles in the atmosphere play a critical role in our understanding of air quality, human and ecosystem health and the mechanisms governing the Earth's climate. Monitoring long term spatial and temporal changes in amount fractions of regulated air pollutants, greenhouse gases, precursors to secondary pollutants (e.g. ozone and particulate matter) and particle number and size distributions are essential to establish the scientific links and feedbacks between atmospheric composition, air quality and climate and to ensure legislative compliance. Ambient amount fractions and stable isotope ratios of many trace gases as well as particle number concentrations and size distributions are routinely observed within networks of monitoring sites and on mobile measurement platforms around the globe. Ensuring the quality and comparability of all these datasets is critical to improve reliability and reduce uncertainty in our understanding of the Earths system. This session invites contributions that seek to address the fundamental metrology needed to underpin long term ambient monitoring of trace gases and particles ensuring coherent and comparable measurements.

Significant uncertainties exist in our understanding of the CO2 and CH4 fluxes between land or ocean and atmosphere on regional and global scales. Remotely-sensed CO2 and CH4 observations provide a significant potential for improving our understanding of the natural carbon cycle and for the monitoring of anthropogenic emissions. Over the last few years, remote sensing technologies for measuring CO2 and CH4 from space, aircraft, and from the ground made great advances and new passive and active instruments from different platforms became available offering unprecedented accuracy and coverage.

This session is open to contributions related to all aspects of remote sensing of the greenhouse gases CO2 and CH4 from current, upcoming and planned satellite missions (e.g., OCO-2, TanSat, Sentinel 5P), as well as ground-based (e.g., TCCON), aircraft, other remote sensing instruments. This includes, e.g., advances in retrieval techniques, instrumentational concepts, and validation activities, but we specifically encourage contributions that focus on the interpretation of observations in respect to natural fluxes or anthropogenic emissions.

Accurate and precise atmospheric measurements of greenhouse gas (GHG) concentrations reveal the rapid and unceasing rise of global GHG concentrations due to human activity. The resulting increases in global temperatures, sea-level, glacial retreat, and other negative impacts are clear. In response to this evidence, nations, states, and cities, private enterprises and individuals have been accelerating GHG reduction efforts while meeting the needs of global development. The urgency, complexity and economic implications of GHG reductions demand strategic investment in science-based information for planning and tracking emission reduction policies and actions. In response, the World Meteorological Organization (WMO) Global Atmosphere Watch Program (GAW) and its partners have initiated the development of an Integrated Global Greenhouse Gas Information System (IG3IS). IG3IS combines atmospheric GHG concentration measurements and human-activity data in an inverse modeling framework to help decision-makers take better-informed action to reduce emissions of greenhouse gases and pollutants that reduce air quality. This service is based on existing and successful measurement and analysis methods and use-cases for which the scientific and technical skill is proven or emerging.
This session intends to gather presentations from researchers and decision-makers (user-community) on the development, implementation and use of atmospheric measurement-based “top-down” and data-driven “bottom-up” GHG emission inventory estimates, and the combination of both approaches, explicit in space and time, to deliver actionable emissions information at scales where human activity occurs and emission reduction is most effective. This session is part of the EGU General Assembly 2019 30th anniversary celebration of the WMO’s Global Atmosphere Watch Program and its commitment to science-based services.

Anthropogenic methane emissions are responsible for roughly one quarter of net radiative forcing from GHGs. Its short atmospheric lifetime makes its mitigation an impactful way to reduce the near-term rate of warming. Atmospheric observations can provide valuable information to (1) reduce uncertainty on magnitude of emissions (2) attribute emissions to specific sources and (3) identify mitigation opportunities.
This session solicits research that focuses on methane emissions from human activities (e.g., fossil fuel infrastructure, rice production, ruminants, landfills and waste sector). We encourage submissions that highlight how atmospheric observations -at different scales- better constrain the magnitude of different emission sources and provide information that can guide relevant stakeholders to reduce emissions.

Public information:
Anthropogenic methane emissions are responsible for roughly one quarter of net radiative forcing from GHGs. We will present research that focuses on methane emissions from human activities (e.g., fossil fuel infrastructure, rice production, ruminants, landfills and waste sector).

Understanding atmospheric transport of trace species and aerosols is a topic that critically depends on bringing modeling and observational efforts together. The purpose of this session is to enable such connections, with a secondary focus on Lagrangian modeling of the atmosphere.

Vertical and long-range transport of trace species and aerosols are key factors controlling their concentrations and variability. Various surface emissions have a strong direct influence on the upper troposphere via several vertical transport processes, especially cumulus convection and lifting associated with frontal systems (warm and cold conveyor belts). Downward transport occurs via accompanying subsidence, while precipitation scavenging is one of the key sinks for many gases and aerosols. Long-range and intercontinental transport result in measurable enhancements of gas and aerosol concentrations in populated and agricultural regions due to industrial and biomass burning emissions thousands of kilometers upstream. Even many "remote" marine regions are far from being free from the direct influence of relatively short-lived anthropogenically produced gases and aerosols produced over far away continents. Additional processes such as stratosphere-troposphere exchange and lightning can also influence the chemical composition of downwind locations. Numerous methods have been applied to study transport-related issues, including targeted and long-term in-situ measurements as well as remote sensing (ground-based and satellite) and models (cloud-scale to global).

Lagrangian models are a very important research tool in this context, yet numerous scientific issues remain. We therefore invite studies contributing to advancing Lagrangian models, including the improvement of parameterizations of atmospheric processes, the quantitative assessment of uncertainties, improving model performance, and the proper coupling of Lagrangian models to Eulerian Numerical Weather Prediction and General Circulation models. In addition we invite contributions from applied Lagrangian research, involving observational data. We specially encourage those studies which synergistically combine various types of models and observations.

Reactive halogen species can have an important influence on the chemistry of the troposphere. For instance chlorine atoms react faster with most hydrocarbons than OH does and inorganic bromine and iodine can catalytically destroy tropospheric ozone and oxidise mercury. These reactions have been shown to be important in environments as different as the polar troposphere during the springtime ozone depletion events, the boundary layer over salt lakes, and volcanic plumes. There is strong evidence that halogens play a spatially even wider role in the marine boundary layer and free troposphere for ozone destruction, changes in the ratios of OH/HO2 and NO/NO2, destruction of methane, in the oxidation of mercury and in the formation of secondary aerosol. There are indications that both, oceanic sources as well as the chemistry of halogens and volatile organic compounds (VOCs) and oxygenated VOCs (OVOCs) in the tropics are linked with potential implications not only for the photochemistry but also the formation of secondary organic aerosol (SOA). It has been shown how the variability in iodine´s distribution in the ocean can have an impact on iodine production and ozone loss in both the ocean surface and throughout the troposphere. Marine emissions of active halogens have been linked to further potential impacts on oxidants loading in coastal cities. Finally, bromine and iodine are also being proposed as proxies of past sea ice variability.

We invite contributions in the following areas dealing with tropospheric halogens on local, regional, and global scales:

- Model studies: Investigations of the chemical mechanisms leading to release, transformation and removal of reactive halogen species in the troposphere. Studies of consequences of the presence of reactive halogen species in the troposphere.

- Laboratory studies: Determination of gas- and aqueous-phase rate constants, study of complex reaction systems involving halogens, Henry's law and uptake coefficients, UV/VIS spectra, and other properties of reactive halogen species. Biogeochemical controls on iodide formation and loss in the ocean to improve the current parameterizations for iodine emission.

- Field experiments and satellite studies: Measurements of inorganic (X, XO, HOX, XONO2, ..., X = Cl, Br, I) and organic (CH3Br, CHBr3, CH3I, RX, ...) reactive halogen species and their fluxes in the troposphere with in situ and remote sensing techniques.

- Measurements and model studies of the abundance of (reactive) halogen species in volcanic plumes and transformation processes and mechanisms.

- All aspects of tropical tropospheric halogens and links to (O)VOCs: their chemistry, sources and sinks, and their impact on local, regional, and global scales.

The session will cover all aspects of polar stratospheric ozone, other species in the polar regions as well as all aspects of polar stratospheric clouds. Special emphasis is given to results from recent polar campaigns, including observational and model studies.

We encourage contributions on chemistry, microphysics, radiation, dynamics, small and large scale transport phenomena, mesoscale processes and polar-midlatitudinal exchange. In particular, we encourage contributions on ClOx/BrOx chemistry, chlorine activation, NAT nucleation mechanisms and on transport and mixing of processed air to lower latitudes.

We welcome contributions on polar aspects of ozone/climate interactions, including empirical analyses and coupled chemistry/climate model results and coupling between tropospheric climate patterns and high latitude ozone as well as representation of the polar vortex and polar stratospheric ozone loss in global climate models.

We particularly encourage contributions from the airborne POLSTRACC field campaign (Polar Stratosphere in a Changing Climate) and related activities, which aim at providing new scientific knowledge on the Arctic lowermost stratosphere and upper troposphere in a changing climate. Contributions from WMO's Global Atmosphere Watch (GAW) Programme and from the Network for the Detection of Atmospheric Composition Change (NDACC) are also encouraged.

Variations in stratospheric aerosol -- arising primarily from sporadic volcanic eruptions -- are an important contributor to climate variability. Major volcanic eruptions have led to pronounced decreases in global surface temperature over seasonal-to-decadal timescales.

The transition from the unusual 1998-2002 period of a “fully decayed to quiescence” stratospheric aerosol layer, into a more typical period of modest volcanic activity temporarily offset a substantial proportion of the subsequent decadal forcing from increased greenhouse gases.

Advancing our understanding of the influence of volcanoes on climate relies upon better knowledge of the radiative forcings of past eruptions and the microphysical, chemical and dynamical processes which affect the evolution of stratospheric aerosol properties. This can only be achieved by combining information from satellite and in-situ observations of recent eruptions, stratospheric aerosol modelling activities, and reconstructions of past volcanic histories from proxies.

This session seeks presentations from research aimed at better understanding the stratospheric aerosol layer and its volcanic perturbations through the post-industrial period (1750-present) and also those further back in the historical record.

This year contributions addressing volcanic influences on atmospheric composition, such as changes in stratospheric water vapour, ozone and other trace gases are also particularly encouraged.

The session also aims to highlight research on volcanoes and climate contributing to current international SPARC-SSiRC, CMIP6-VolMIP, CMIP6-PMIP, and PAGES-VICS co-ordinated activities.

Over the past few years, major technological advances allowed to significantly increase both the spatial coverage and frequency bandwidth of geochemical and geophysical observations at active volcanoes. Establishment of high-rate GPS networks, continuous gravity meters, dense arrays of broad-band seismometers, and networks of instruments for the quantitative measurement of volcanic gas emissions now permits an unprecedented, multi-parameter vision of the surface manifestations of mass transport beneath volcanoes. Accompanying these progresses are new models and processing techniques leading to innovative paradigms for the interpretation and inversion of observational data. Within this context, this session aims at bringing together a multidisciplinary audience to discuss about the most recent innovations in monitoring approaches and to present observations, methods and models that increase our understanding of volcanic processes.

We welcome contribution related to (1) New instruments and techniques for the measurement of geophysical and geochemical parameters, from in-situ methods to ground-, air- and space-based remote sensing techniques; (2) Reports of significant case histories, documenting the relationships between the measured parameters and the evolving volcanic processes; (3) New modelling frameworks for the interpretation of the observed data, and their significance in terms of eruption forecasting.

The session will provide an opportunity to discuss volcanic activity from a monitoring perspective on a wide range of volcanoes. We therefore encourage submission of papers that are easily understandable to a broad, multi-disciplinary audience.

Areas found at plate boundaries are characterized by the presence of seismic, volcanic and geothermal activity. These processes are enhanced by the circulation of hydrothermal fluids in the crust, which transport volatiles from the deep crust or mantle to the surface. Certainly not limited to plate boundaries, as magma rises from depth, decreasing pressure allows volatile species to partition to the gas phase. Bubbles form, grow, coalesce and gases start to flow through vesiculated magma. Eventually, fluids escape towards the surface using tectonic structures and are released in the atmosphere, in some cases diffused through a soil or bubbling through a water pool, in other cases forming large plumes or explosive eruption columns. Fluids play an important role in earthquake generation.
Geochemical and isotope composition of gases deriving from different settings can trace sources and chemical and physical processes, providing information about deep earth. Moreover, volatiles play a key role in magma transport and have significant impact on the style and timing of volcanic eruptions. In addition, noble gases deriving from the deep earth can provide important information about their crust or mantle origin because these gases hardly react with other materials during migration. While carbon dioxide is one of the major constituents in volcanic/geothermal areas, methane, dominating sedimentary low heat flow areas, is often linked to subsurface hydrocarbon reservoirs that due to tectonic discontinuities are released in the atmosphere. Furthermore, sulfur dioxide emissions that take place in volcanic environments can cause acid rain, influence aerosol formation and, if an eruption column reaches the stratosphere, cause global dimming and a decrease in Earth’s surface temperatures for years. Similarly, halogens can dramatically impact proximal ecosystems, influence the oxidation capacity of the troposphere and alter the stratospheric ozone layer. Gas composition and flux may change with time, reflecting variations in the system. Measuring gases therefore constitutes a powerful tool for monitoring and understanding Earth.
This session aims to merge different geo-disciplines and bring together researchers interested in the comprehension of the degassing processes that take place in various geodynamic regimes. Furthermore, identify the impact that the emissions can have on terrestrial environment, atmospheric composition, climate and human health at various temporal and spatial scales. We invite contributions discussing novel measurement techniques, field measurements, direct and remote ground- and space-based observations and modeling studies of degassing can provide new insights into volcanic, tectonic and atmospheric processes on local and global scales.

This session has been created from sessions AS3.31 ‘Radiative effects and global aerosol forcing estimates of natural and anthropogenic aerosols’ (Convenors: Cathrine Lund Myhre, Elisabeth Andrews, Andreas Petzold, Bjørn Samset, Michael Schulz) and session AS3.32 ‘Natural Aerosols from Pre-Industrial to Present Day and into the Future’ (Convenors: Catherine Scott, Stephanie Fiedler, Kerstin Schepanski, Hugh Coe, Douglas Hamilton).

Aerosol radiative effects are an important aspect of the climate system that have both anthropogenic and natural contributions. This broad session focuses on the life cycle and radiative effects of all aerosol species present in the atmosphere.

One key topic is the radiative properties and effects of aerosols (e.g. black and brown carbon, mineral dust, biomass burning and hygroscopic aerosols) and model evaluation using aerosol observations. Today, ever more high quality data of aerosol optical properties, aerosol humidification, size distributions, aerosol light absorption and aerosol extinction vertical profiles have become available through international cooperation such as ACTRIS, GAW and NOAA networks. At the same time exhaustive global aerosol model results from multiple groups have been assembled in the AeroCom database, and rapid developments are being made in advance of CMIP6.

A better understanding of the role of natural aerosols in the atmosphere is essential for accurately determining anthropogenic radiative forcing and the climate response. In this session we will explore what we consider to be natural aerosols (i.e., primary aerosols and those formed from precursor gases emitted by natural sources, such as: wildfire, dust, volcanoes and the marine and terrestrial biospheres) and what we can observe about them in today’s atmosphere. Crucial questions include:
- How can we distinguish between truly natural aerosols and those whose emissions or formation are influenced by anthropogenic activities?
- How have the contributions of natural aerosols to atmospheric composition changed over time?
- How well do we understand the lifecycle of natural aerosols in the atmosphere in the absence of anthropogenic influence?
- Can we identify any pristine environments in the present day that can help us understand the pre-industrial atmosphere?
- How well are natural aerosols represented in Earth System Models and which observations can be used to evaluate them?

We welcome contributions relating to the use of observations and/or modelling to inform us about past, present-day and future aerosol-climate interactions.

Volatile Organic Compounds (VOCs) in the atmosphere are globally dominated by a number of primary emission sources. These include biogenic sources (e.g. emissions from plants, flowers) or microbial VOCs (mVOCs), as well as anthropogenic and pyrogenic emissions. Once in the atmosphere, VOCs are oxidized and serve as precursors of secondary organic aerosol. They also contribute to the formation of tropospheric ozone, and can affect atmospheric oxidants. Mechanistic understanding of chemical pathways and surface-atmosphere exchange in rural and urban environments requires synergy between measurements at different spatiotemporal scales including laboratory oxidation experiments, embracing the broad diversity of VOC sources in the atmosphere. From a direct health perspective the largest human exposure to VOCs is likely not outdoors but in the indoor atmosphere. The use of solvents and consumer-care products by humans have also emerged as a prominent source of outdoor atmospheric VOCs. Extension of the range of VOCs measured in urban environments reveal large contributions of longer-chain semivolatile VOCs, and recent measurement technologies for extremely low volatility compounds (ELVOC) have bridged the gas-aerosol phase continuum.
We encourage a wide range of submissions of contributions based on in-situ measurements of VOCs at different scales, outdoors and indoors, flux measurements of emission and deposition processes, satellite observations, laboratory experiments and modeling.

Plant ecosystems exchange reactive trace gases, such as nitrogen oxides (NOx), ozone, and volatile organic compounds (VOCs), and particles. While some of these compounds are anthropogenically produced, many are biotic in origin and are emitted in-situ or produced from rapid photochemistry in the canopy. The oxidation products include low-volatility organic compounds that readily partition to the aerosol phase, particularly in the presence of anthropogenic pollutants such as ammonium, nitrate and sulphate. In addition to being strong sources, soil and leaves represent major sinks of these reaction products, with deposition to the surface also as a function of surface wetness and uptake into the leaf via the stomata. The canopy region thus represents a dynamic and rapidly changing environment in which a myriad biological, chemical and physical processes occur over very short time and spatial scales. Advanced techniques of flux measurements provide good knowledge of the overall net fluxes of these compounds above canopies, while additional in-canopy measurements enable more detailed study and understanding of the individual processes and reactions driving these fluxes. These rapidly advancing measurements can support parametrization of models for a mechanistic understanding of in-canopy dynamics of deposition and emission of these reactive gases, which can in turn allow fuller interpretation of in-situ measurements and inform the design of field experiments to test specific hypotheses. This session, sponsored by ILEAPS (Integrated Land Ecosystem Atmosphere Process Study), encourages the submission of contributions based on in-situ measurements and/or modeling that improve our understanding of biosphere-atmosphere exchange of reactive gases and aerosols and in-canopy processes.

The Amazon forest is the world’s largest intact forest landscape. Due to its large biodiversity, carbon storage capacity, and role in the hydrological cycle, it is an extraordinary interdisciplinary natural laboratory of global significance. In the Amazon rain forest biome, it is possible to study atmospheric composition and processes, biogeochemical cycling and energy fluxes at the geo-, bio-, atmosphere interface under near-pristine conditions for a part of the year, and under anthropogenic disturbance of varying intensity the rest of the year. Understanding its current functioning at process up to biome level is elemental for predicting its response upon changing climate and land use, and the impact this will have on global scale.

This session aims at bringing together scientists who investigate the functioning of the Amazon and comparable intact forest landscapes across spatial and temporal scales by means of remote and in-situ observational, modeling, and theoretical studies. Particularly welcome are also presentations of novel, interdisciplinary approaches and techniques that bear the potential of paving the way for a paradigm shift.

Organic material can make up a substantial fraction of ambient particulate matter, both in polluted urban areas and in cleaner rural and remote regions. Therefore they have the ability to impact the Earth radiative balance and human health at local, regional and global scales. Aerosols are made up of a complex mixture of inorganic and organic species with a wide range of functionalities and volatilities, making them one of the most challenging components of the atmosphere to characterize. Once organic compounds are emitted to the atmosphere they can undergo complex chemical and physical processes. The chemical processes involving aerosol species can also lead to changes in the physicochemical properties of ambient particles, such as their hygroscopicity, morphology and phase, diffusion of water and SVOCs, light scattering and absorption. Thus even with extensive study, our understanding of their sources, formation, evolution and vertical distribution in the atmosphere remains limited.

This session welcomes presentations that discuss the sources and evolution of organic aerosols in the atmosphere and how atmospheric processes transform ambient aerosols both in terms of their chemical composition and their physical properties.

Fine-particle pollution associated with haze threatens the health of more than 1 billion people in China. Extremely high PM2.5 concentrations are frequently observed especially during the winter haze event in northern China. Even after accounting for aerosol-radiation-meteorology feedback and improving the emission inventory, state-of-the-art models still fail to capture the observed high PM2.5 concentrations, suggesting the missing of key chemistry for the secondary aerosol formation. To improve the prediction and control strategy of PM2.5, we are in urgent need of a better understanding of the chemistry of secondary aerosol formation. Thus we propose the session "Multiphase chemistry of secondary aerosol formation under severe haze" to promote the research and discussion on this topic which is highly relevant for both atmospheric chemists and the public.

The session is open for all submissions which addresses, but is not limited to, the following questions concerning secondary aerosol formation: What are the key oxidation pathways leading to aerosol formation under clean and polluted conditions? What is the role of multiphase chemistry versus gas phase chemistry? Are laboratory determined kinetic data of multiphase chemistry directly applicable for ambient conditions and if not, how to derive and determine the reaction kinetics relevant for ambient conditions? What is the aerosol particles’ and droplets’ pH and how does it influence the multiphase chemistry? What is the role of the RH, temperature, mixing state and aerosol phase state in multiphase chemistry and how does aerosol mixing state play a role? What's the contribution of aqueous secondary organic aerosol (SOA) formation under highly polluted conditions?

A special issue of the same topic has already been approved and launched in the EGU journal "Atmospheric Chemistry and Physics".

The atmospheric water cycle is a key component of the climate system,
and links across many scientific disciplines. Processes and dynamics at
different scales interact throughout the atmospheric life cycle of
water vapour from evaporation to precipitation. This session sets the
focus on processes, dynamics and characteristics at the evaporation
sources, during moisture transport, and at the precipitation sinks as
observed from in-situ and remote sensing, recorded by (paleo)climate
archives, and as simulated for past, present and future climates.

We invite studies

* focusing on extensive transient features of the atmospheric water
cycle, such as Atmospheric Rivers, Cold-Air Outbreaks, warm conveyor
belts, tropical moisture exports, precipitation extremes, and the
monsoon systems.

* investigating the large-scale drivers of the water cycle features’
variability and change by looking at observations, reanalyses or
global/regional climate simulations, in order to improve their
predictability

* involving and connecting results from field campaigns (YOPP, MOZAIC,
NAWDEX), reanalysis data, indicators of past hydroclimate from climate
proxies such as ice cores and stalagmites, and model predictions of the
future evolution of the atmospheric water cycle,

* applying methods such as stable isotopes as physical tracers in the
water cycle, tagged water tracers, and Lagrangian moisture source
diagnostics to identify source-sink relationships and to evaluate model
simulations of the water cycle,

* describing the global and regional state of the atmospheric cycle
with characteristics such as the recycling ratio, life time of water
vapour, and moisture transport distance

We particularly encourage contributions to link across neighbouring
disciplines, such as atmospheric science, climate, paleoclimate,
cryosphere, and hydrology.

In recent decades, quantitative methods have become increasingly important in the field of palaeoenvironmental, palaeoclimatic and palaeohydrological reconstruction, due to the need for comparison between different records and to provide boundary conditions for computational modelling. Continental environmental archives (e.g. speleothems, lakes, land snails, rivers, or peatlands) are often highly temporally resolved (subdecadal to seasonal) and may provide more direct information about atmospheric and hydrological processes than marine archives. The wide variety of archive types available on land also allows for intercomparison and ground-truthing of results from different techniques and different proxies, and multi-proxy reconstructions from the same archive can disentangle local and supra-regional environmental conditions. This approach is particularly useful for the reconstruction of hydrological dynamics, which are challenging to reconstruct due to their high spatial variability, signal buffering, nonlinearities and uncertainties in the response of available paleoclimate archives and proxies. For example, climate-independent factors such as land cover change can affect the local to regional water availability recorded in proxies.

This session aims to highlight recent advances in the use of innovative and quantitative proxies to reconstruct past environmental change on land. We present studies of various continental archives, including but not limited to carbonates (caves, paleosols, snails), sediments (lakes, rivers, alluvial fans), and biological proxies (tree rings, fossil assemblages, plant biomarkers). We particularly include studies involving the calibration of physical and chemical proxies that incorporate modern transfer functions, forward modeling and/or geochemical modeling to predict proxy signals, and quantitative estimates of past temperature and palaeohydrological dynamics. We also include reconstructions of temperature and hydrologic variability over large spatial scales and paleoclimate data assimilation. This session will provide a forum for discussing recent innovations and future directions in the development of terrestrial palaeoenvironmental proxies on seasonal to multi-millennial timescales.

This session aims to highlight recent advances in the use of innovative and quantitative proxies to reconstruct past environmental change on land. We welcome studies of any continental archive, including but not limited to carbonates (caves, paleosols, snails), sediments (lakes, rivers, alluvial fans), ice, and biological proxies (tree rings, fossil assemblages, plant biomarkers). We particularly encourage studies involving the calibration of physical and chemical proxies that incorporate modern transfer functions, forward modeling and/or geochemical modeling to predict proxy signals, and quantitative estimates of past temperature and precipitation amounts. We also welcome reconstructions of temperature and hydrologic variability over large spatial scales, including paleoclimate data assimilation studies. This session will provide a forum for discussing recent innovations and future directions in the development of terrestrial palaeoenvironmental proxies on seasonal to multi-millennial timescales.

Prediction skill of hydro-meteorological forecasting systems has remarkably improved in recent decades. Advances in both weather and hydrology models, linked to the availability of more powerful and efficient computational resources, allowed the development of even more complex systems based on the combination of spatially distributed physically-based hydrologic- and hydraulic models with deterministic and/or ensemble meteorological forecasting systems. Coupled atmosphere-hydrological modeling aims at describing the full atmospheric-terrestrial regional water cycle, i.e. extending from the top of the atmosphere, through the boundary layer, via the land surface and subsurface till lateral flow in the groundwater and in the river beds. Fully two-way coupled model systems thereby give the possibility to study long range feedbacks between groundwater, soil moisture redistribution and precipitation. Via improved and completed process descriptions fully coupled modeling may also increase the performance of hydrometeorological predictions of various spatial and temporal scales.
The objective of the session is to create a valuable opportunity for the interdisciplinary exchange of ideas and experiences among atmospheric-hydrological modelers and members of both hydrology- and Earth System modeling communities. Contributions are invited dealing with the complex interactions between surface water, groundwater and regional climate, with a specific focus on those presenting work on the development or application of one-way (both deterministic and ensemble) or fully-coupled hydrometeorological prediction systems for floods/flash-floods, droughts and water resources. Presentations of inter-comparisons between one-way and fully-coupled hydrometeorological chains are encouraged, such as contributions on novel one-way and fully-coupled modeling systems that bridge spatial scales through dynamic regridding or upscaling/downscaling methodologies. Also, presentations addressing data assimilation in coupled model systems are welcome. Likewise abstracts are invited on field experiments and testbeds equipped with complex sensors and measurement systems allowing multi-variable validation of such complex modeling systems.

Ensemble hydro-meteorological prediction systems have higher forecasting skills than their deterministic counterparts, which in turn can improve risk assessment decision-making in operational water management. Ensemble forecasts are now common many operational settings, such as flood and drought forecasting, and can be used in applications from forecasting extreme events to optimisation of water resources allocation. However, moving from deterministic forecasting systems to a probabilistic framework poses new challenges but it also opens new opportunities for the developers and users of ensemble forecasts to improve their systems.

This session brings together scientists, forecasters, practitioners and stakeholders interested in exploring the use of ensemble hydro-meteorological forecast techniques in hydrological applications: e.g., flood control and warning, reservoir operation for hydropower and water supply, transportation and agricultural management. The session will also explore new forecast products and systems in terms of their implementation and practice for real-time forecasting.

Contributions will cover, but are not restricted to, the following topics:
- The design of ensemble prediction systems
- Requirements and techniques to improve the skill of hydro-meteorological ensemble forecasting systems
- Methods to bias correct and calibrate ensemble forecasts
- Methods to assess the quality or benchmark the performance of ensemble forecasts
- Approaches to deal with forecast scenarios in real-time
- Strategies for balancing human expertise and automation in ensemble forecasting systems
- Challenges of the paradigm shift from deterministic to ensemble forecasts
- Methods and products that include forecaster knowledge to improve the interpretation of ensemble forecasts
-Use of cost/loss scenarios for optimising systems
- Approaches for efficient training (including role-playing games) on the use and value of ensemble predictions.

The session welcomes new experiments and practical applications showing successful experiences, as well as problems and failures encountered in the use of uncertain forecasts and ensemble hydro-meteorological forecasting systems. Case studies dealing with different users, temporal and spatial scales, forecast ranges, hydrological and climatic regimes are welcome.

Solicited speaker Niko Wanders from Utrecht University: From seasonal forecasting to water management decisions: challenges and opportunities

The session is part of the HEPEX international initiative: www.hepex.org

Snow cover characteristics (e.g. spatial distribution, surface and internal physical properties) are continuously evolving over a wide range of scales due to meteorological conditions, such as precipitation, wind and radiation.
Most processes occurring in the snow cover depend on the vertical and horizontal distribution of its physical properties, which are primarily controlled by the microstructure of snow (e.g. density, specific surface area). In turn, snow metamorphism changes the microstructure, leading to feedback loops that affect the snow cover on coarser scales. This can have far-reaching implications for a wide range of applications, including snow hydrology, weather forecasting, climate modelling, and avalanche hazard forecasting or remote sensing of snow. The characterization of snow thus demands synergetic investigations of the hierarchy of processes across the scales ranging from explicit microstructure-based studies to sub-grid parameterizations for unresolved processes in large-scale phenomena (e.g. albedo, drifting snow).

This session is therefore devoted to modelling and measuring snow processes across scales. The aim is to gather researchers from various disciplines to share their expertise on snow processes in seasonal and perennial snowpacks. We invite contributions ranging from “small” scales, as encountered in microstructure studies, over “intermediate” scales typically relevant for 1D snowpack models, up to “coarse” scales, that typically emerge for spatially distributed modelling over mountainous or polar snow- and ice-covered terrain. Specifically, we welcome contributions reporting results from field, laboratory and numerical studies of the physical and chemical evolution of snowpacks, statistical or dynamic downscaling methods of atmospheric driving data, assimilation of in-situ and remotely sensed observations, representation of sub-grid processes in coarse-scale models, and evaluation of model performance and associated uncertainties.

This session is linked closely to the session HS2.1.2/CR3.11. While the focus of our session is on monitoring and modelling snow processes across scales, session HS2.1.2/CR3.11 addresses monitoring and modelling of snow for hydrologic applications.

Air-sea fluxes of biogeochemically active constituents have significant impacts on global biogeochemistry and climate. Increasing atmospheric deposition of anthropogenically-derived nutrients (e.g., nitrogen, phosphorus, iron) to the ocean influences marine productivity and has associated impacts on oceanic CO2 uptake, and emissions to the atmosphere of climate active species (e.g., nitrous-oxide (N2O), dimethyl-sulfide (DMS), marine organic compounds and halogenated species). These oceanic emissions of reactive species and greenhouse gases influence atmospheric chemistry and global climate, and induce potentially important chemistry-climate feedbacks. While advances have been made by laboratory, field, and modelling studies over the past decade, we still lack understanding of many of the physical and biogeochemical processes linking atmospheric deposition, nutrient availability, marine biological productivity, and the biogeochemical cycles governing air-sea fluxes of these climate active species. Atmospheric inputs of other toxic substances, e.g., lead, cadmium, copper, and persistent organic pollutants, into the ocean are also of concern.
This session will address the atmospheric deposition of nutrients and toxic substances to the ocean, their impacts on ocean biogeochemistry, the air-sea fluxes of climate active species and potential feedbacks to climate. We welcome new findings from both measurement programmes and atmospheric and oceanic models.
This session is jointly sponsored by GESAMP Working Group 38 on ‘The Atmospheric Input of Chemicals to the Ocean’, the Surface Ocean-Lower Atmosphere Study (SOLAS) , and the International Commission on Atmospheric Chemistry and Global Pollution (ICACGP).

Modeling soil and vadose zone processes is vital for estimating physical states, parameters and fluxes from the bedrock to the atmosphere. While the media soil, air and water physically affect biogeochemical processes, transport of nutrients and pollutants, their implications on ecosystem functions and services, and terrestrial storage capacities are vital to the understanding of global, land use and climate change. This session aims to bring together scientists advancing the current status in modelling soil processes from the pore to the catchment and continental scale. We welcome contributions with a specific focus on soil hydrological processes but also those that address the role of soil structure on land surface processes, soil biogeochemical processes and their interactions with hydrology, transport of pollutants, soil vegetation atmosphere modelling and root-soil processes.

Clouds play an important role in the polar climate due to their interaction with atmospheric radiation and their role in the hydrological cycle linking poleward water vapour transport with precipitation, thereby affecting the mass balance of the polar ice sheets. Cloud-radiative feedbacks have also an important influence on sea ice. Cloud and precipitation properties depend strongly on the atmospheric dynamics and moisture sources and transport, as well as on aerosol particles, which can act as cloud condensation and ice nuclei.

This session aims at bringing together researchers using observational (in-situ, aircraft, ground-based, and satellite-based remote sensing) and/or modeling approaches (at various scales) to improve our understanding of polar tropospheric clouds, precipitation, and related mechanisms and impacts. Contributions are invited on various relevant processes including (but not limited to):
- Drivers of cloud/precipitation microphysics at high latitudes,
- Sources of cloud nuclei both at local and long range,
- Linkages of polar clouds/precipitation to the moisture sources and transport,
- Relationship of the poleward moisture transport to processes in the tropics and extra-tropics, including extreme transport events (e.g., atmospheric rivers, moisture intrusions),
- Relationship of moisture/cloud/precipitation processes to the atmospheric dynamics, ranging from synoptic and meso-scale processes to teleconnections and climate indices,
- Role of the surface-atmosphere interaction in terms of mass, energy, and cloud nuclei particles (evaporation, precipitation, albedo changes, cloud nuclei sources, etc)
- Effects that the clouds/precipitation in the Polar Regions have on the polar and global climate system, surface mass and energy balance, sea ice and ecosystems.

Papers including new methodologies specific to polar regions are encouraged, such as (i) improving polar cloud/precipitation parameterizations in atmospheric models, moisture transport events detection and attribution methods specifically in the high latitudes, and (ii) advancing observations of polar clouds and precipitation. We would like to emphasize collaborative observational and modeling activities, such as the Year of Polar Prediction (YOPP), Polar-CORDEX, the (AC)³ project on Arctic Amplification, SOCRATES and other campaigns over the Southern Ocean/Antarctica, and encourage related contributions.

The session is endorsed by the SCAR Antarctic Clouds and Aerosols Action Group.

Young scientist/student presentations are especially encouraged and we will reserve several oral units for such papers in this session.

The rapid decline of Arctic sea ice in the last decade is a dramatic indicator of climate change.  The last 12 years have seen lower Arctic summer sea ice extents than in the previous 29 years of satellite records. The Arctic sea ice cover is now thinner, weaker and drifts faster. The ocean is also changing, the volume of freshwater stored in the Arctic and has increased as have the inputs of coastal runoff from Siberia and Greenland. Concurrently inflows from the Atlantic and Pacific Oceans have warmed. As the global surface temperature rises, the Arctic Ocean is speculated to become seasonally ice-free in the 21st century, which prompts us to revisit our perceptions of the Arctic system as a whole. What could the Arctic look like in the future? How are the present changes in the Arctic going to affect the lower latitudes? What aspects of the changing Arctic should future observations and modelling programs address? The scientific community is investing considerable effort in organising our current knowledge of the physical and biogeochemical properties of the Arctic, exploring poorly understood coupled atmosphere-sea-ice-ocean processes to improve prediction of future changes in the Arctic.
 
In this session, we invite contributions on a variety of aspects of past, present and future climates of the Arctic. We encourage submissions addressing interaction between ocean, atmosphere and sea ice and on studies linking changes in the Arctic to the global ocean. Submissions with a focus on emerging cryospheric, oceanic and biogeochemical processes and their implications are particularly welcome. The session promotes results from current Arctic programmes and discussions on future plans for Arctic Ocean modelling and measurement strategies. This session is cosponsored by the CLIVAR /CliC Northern Ocean Regional Panel (NORP) that aims to facilitate progress and identify scientific opportunities in (sub)Arctic ocean-sea-ice-atmosphere research.

The Arctic sea ice and high latitude atmosphere and oceans have experienced significant changes over the modern observational era. The polar climate is crucial for the Earth’s energy and water budget, and its variability and change have direct socio-economic and ecological impacts. Thus, understanding high-latitude variability and improving predictions of high latitude climate is highly important for society. Predictability studies indicate that decadal to multi-decadal variations in the oceans and sub-seasonal to multi-year sea ice variations are the largest sources of predictability in high latitudes. However, dynamical model predictions are not yet in the position to provide us with accurate predictions of the polar climate. Main reasons for this are the lack of observations in high latitudes, insufficient initialization methods and shortcomings of climate models in representing some of the important climate processes in high latitudes.
This session aims for a better understanding and better representation of the mechanisms that control high latitude climate variability and predictability in both hemispheres at sub-seasonal to multi-decadal time-scales in past, recent and future climates. Further, the session aims to discuss ongoing efforts to improve climate predictions at high latitudes at various time scales (as e.g. usage of additional observations for initialization, improved initialization methods, impact of higher resolution, improved parameterizations) and potential teleconnections of high latitude climate with lower latitude climate. We also aim to link polar climate variability and predictions to potential ecologocal and socio-economic impacts and encourage submissions on this topic.
This session offers the possibility to present results from the ongoing projects and research efforts on the topic of high-latitude climate variability and prediction, including, but not limited to Year of Polar Prediction (YOPP), and the ARCPATH-project (Arctic Climate Predictions - Pathways to Resilient, Sustainable Societies).

The nature of science has changed: it has become more interconnected, collaborative, multidisciplinary, and data intensive. Accordingly, the main aim of this session is to create a common space for interdisciplinary scientific discussion, where EGU-GA delegates involved in geoscientific networks can share ideas and present the research activities carried out in their networks. The session represents an invaluable opportunity for different networks and their members to identify possible synergies and establish new collaborations, find novel links between disciplines, and design innovative research approaches.

Part of the session will be focused on COST (European Cooperation in Science and Technology) Actions*. The first edition of the session (successfully held in 2018) was actually entirely dedicated to the COST networking programme and hosted scientific contributions stemming from 25 Actions, covering different areas of the geosciences (sky, earth and subsurface monitoring, terrestrial life and ecosystems, earth's changing climate and natural hazards, sustainable management of resources and urban development, environmental contaminants, and big data management). Inspiring and fruitful discussions took place; the session was very well attended. We are looking forward to continuing the dialogue this year and to receiving new contributions from COST Action Members.

Another part of the session will be dedicated to the activities of other national and international scientific networks, associations, as well teams of scientists who are carrying out collaborative research projects.

Finally, the session is of course open to everyone! Accordingly, abstracts authored by scientists not involved in wide scientific networks are most welcome, too! In fact, in 2018 we received a good number of such abstracts, submitted by individual scientists or small research teams who wished to disseminate the results of their studies in front of the multidisciplinary audience that characterizes this session, as an alternative to making a presentation in a thematic session. This may be a productive way to broaden the perspective and find new partners for future interdisciplinary research ventures. We hope to receive this kind of abstracts this year, as well.


-- Notes --

* COST (www.cost.eu) is a EU-funded programme that enables researchers to set up their interdisciplinary research networks (the “Actions”), in Europe and beyond. COST provides funds for organising conferences, workshops, meetings, training schools, short scientific exchanges and other networking activities in a wide range of scientific topics. Academia, industry, public- and private-sector laboratories work together in Actions, sharing knowledge, leveraging diversity, and pulling resources. Every Action has a main objective, defined goals and clear deliverables. This session was started as a follow up initiative of COST Action TU1208 “Civil engineering applications of Ground Penetrating Radar” (2013-2017, www.GPRadar.eu).

Large-scale atmospheric circulation dynamics are the major driver of near surface climatic and environmental variability. Synoptic climatology examines atmospheric circulation dynamics and their relationship with near surface environmental variables. Within synoptic climatological analyses, a wide variety of methods is utilized to characterize atmospheric circulation (e.g., circulation and weather type classification, regime analysis, teleconnection indices). Various linear and non-linear approaches (e.g., multiple regression, canonical correlation, neural networks) are applied to relate the circulation dynamics to diverse climatic and environmental elements (e.g., air temperature, air pollution, floods).

The session welcomes contributions from the whole field of synoptic climatology. This includes application studies for varying regions, time periods (past, present, future) and target variables and in particular contributions on the development and the comparison of methods (e.g., varying circulation type classifications) and conceptual approaches (e.g., circulation types versus circulation regimes).

The large-scale atmospheric circulation strongly influences Earth's climate, both locally and globally, via its transport of energy, moisture, and momentum. While our ability to simulate the global circulation is improving, large model biases and uncertainties in climate change projections persist. Our theoretical understanding of how atmospheric circulations respond to climate changes is also limited, particularly on regional scales and in the presence of zonal asymmetries. Advancing our knowledge of the underlying dynamics is therefore crucial for reliable climate projections and for correctly interpreting palaeoclimate records.

The objective of this session is to advance our mechanistic understanding of atmospheric circulation changes and to analyse their impacts at global and regional scales, specifically on precipitation in past, present, and future climates. We encourage theoretical, observational and modelling contributions on tropical (ITCZ, monsoons, Hadley & Walker circulations, MJO) and extratropical circulations (jet streams, storm tracks, blocking).

Highly productive Eastern Boundary Upwelling Systems (EBUS) play a key role in the global carbon and nitrogen cycles. They also sustain intense fishery activities that could be affected by climate change. EBUS are characterized by a complex interplay of biological, chemical and physical processes taking place in sediments, water column and at the air-sea interface. In particular, physical processes range from regional scales to mesoscale eddies, submesoscale filaments and fronts, down to internal waves and microscale turbulence. They drive the transport of solutes such as nutrients, carbon and oxygen, as well as particulate matter and living organisms. A recent improvement in computational power and new techniques such as multi-nesting approaches, made possible to increase the resolution of regional ocean models down to some hundred meters, allowing to resolve these processes on the fine scale. New observational techniques such as airborne, underway, and autonomous technologies allow for high-resolution adaptive multidisciplinary campaigns. Recent progress in biological/microbial techniques and application of new chemical sensor techniques allow deciphering of biogeochemical patterns with unprecedented high resolution.

Interdisciplinary observational and modeling studies investigating physical, biological and chemical aspects of the major EBUS are welcome. In particular studies which combine observational and modeling efforts, new data analysis techniques and focusing on climate change impacts are of interest.

NEWS: We are glad to announce that Monique Messie (https://www.mbari.org/messie-monique/) will give a solicited contribution to our session.

South America is home to hundreds of millions of people and harbors a wide range of unique and valuable ecosystems and resources. This makes South America, which extends from the tropics to high southern latitudes, vulnerable to a diverse range of climate change impacts. For example, future climate change scenarios suggest tropical South America is a drought hotspot due to its high sensitivity in responding to warming and drying. Thus, it is of great scientific, societal, environmental, and economic interest to better understand how climate varies and is changing over South America.

This session seeks contributions from a wide range of topics focusing on climate research over South America. Topics include, but are not limited to: climate change, climate variability, and extreme events in the past, present, and future using diagnostic, modeling, and statistical approaches.

Tropical ecosystems play an important role for the regional and global climate system through the exchange of greenhouse gases (GHG), water and energy and provide important ecosystem services that we as humans depend on, such as wood, foods, and biodiversity. Historic and recent human activities have, however, resulted in intensive transformation of tropical ecosystems impacting on the cycling of nutrients, carbon, water, and energy.

Here we invite contributions that provide insights on how land-use and land-use change influences biogeochemical cycles and ecohydrology in tropical ecosystems at the plot, landscape, and continental scale. Examples include nitrogen and carbon cycles in soil and vegetation, the exchange of GHG between soil and atmosphere as well as ecosystem and atmosphere, changes in the energy balance, impacts on the water cycle, scaling issues from plots to country to continent; and the influence of management activities (i.e. fertilization, drainage, etc.) on GHG fluxes.

The session covers forests, but also managed land-use systems such as agriculture, pastures or oil palm plantations. Experimental studies (chamber or eddy covariance flux measurements, stable isotopes, sap flux), inventories, as well as remote sensing or modelling studies are welcomed.

The interaction of processes between the land surface, the planetary boundary layer (PBL), and the free troposphere are crucial for the understanding of weather and climate including extremes such as heavy precipitation and droughts. This requires an advanced understanding and modeling of the exchange of momentum, water, energy, and carbon at interfaces. In this session, we present and discuss current research activities contributing to this understanding, including L-A interaction and feedback to the diurnal cycle of the PBL, clouds, and precipitation as well as surface fluxes such as evapotranspiration and entrainment. We accept observational and modeling approaches to address these challenges. With respect to the observations, emphasis is put on the application of new sensor synergies, e.g., using active remote sensing for studying land surface exchange processes and entrainment at the PBL top, which have been addressed in field campaigns. With respect to theoretical understanding and modeling, we are focusing on new insights by feedback diagrams and grey zone experiments down to the large eddy simulation scale.

This session is open to a wide range of contributions on atmospheric sciences in Sub-Saharan Africa, with a focus on tropical regions.

This includes work based on field observations (campaign, long-term), satellite remote sensing and numerical models as well as work targeting socio-economic implications of atmospheric phenomena.

Contributions are invited on various relevant topics, related to Sub-Saharan Africa, including:
* dynamical meteorology;
* atmospheric chemistry, aerosols and associated health impacts
* cloud microphysics and precipitation
* climate variability and change
* radiative processes
One focus of the session is the ongoing DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions over West Africa) project funded by the European Commission under FP7. DACCIWA organized a large international field campaign in June-July 2016 in southern West Africa.

Young scientist/student presentations are especially encouraged and we will reserve several oral units for such papers in this session.

Invited speaker: Chris Taylor (CEH): Overview of Future Climate for Africa program

This session addresses two sub-topics: the small scale variability of precipitation, and the atmospheric water cycle. It adopts a PICO format which aims at employing the most modern and captivating environment of scientific exchange (i.e., a 2-minute oral presentation, nicknamed "2-minute madness", followed by an interactive poster presentation on dedicated touch-screens, https://egu2019.eu/guidelines/pico_presenter_guidelines.html).

Precipitation variability: from drop scale to lot scale

The understanding of small scale spatio-temporal variability of precipitation from seconds in time and drop scale in space to 5 minutes in time and 1 km in space is essential for larger scale studies, including more and more hydrological applications, especially in highly heterogeneous areas (mountains, cities). Nevertheless grasping this variability remains an open challenge. An illustration of the range of scales involved is the ratio between the effective sampling areas of the commonly used point measurement devices (rain gauges and disdrometers) and weather radars, which is greater than 10^7! This session will bring together scientists and practitioners that aim at bridging this scale gap and improving the understanding of small scale precipitation variability, both liquid and solid, as well as its consequences at larger scales.
Contributions addressing one or several of the following issues are especially targeted:
- Novel measurement devices, combinations of devices (both in situ and remote sensors), or experimental set ups enabling to grasp small scale precipitation variability;
- Novel modelling or characterization tools of small scale precipitation variability relying on a wide range of approaches (e.g. scaling, (multi-)fractal, statistic, deterministic, numerical modelling);
- Precipitation drop (or particle) size distribution and its small scale variability, including its consequences for rain rate retrieval algorithms for radars and other remote sensors;
- Physical processes leading to the small-scale rainfall variability
- Examples of hydrological applications where small scale precipitation variability input is required.


The atmospheric water cycle: feedbacks, management, land-use and climate change

Traditionally, hydrologists have always considered precipitation and temperature as input to their models and evaporation as a loss. However, more than half of the evaporation globally comes back as precipitation on land. Land-use changes alter, not only, the local water cycle, but through atmospheric water and energy feedbacks also effect the water cycle in remote locations.
This session aims to:
- show applied studies using fundamental characteristics of the atmospheric branch of the hydrologic cycle on different scales. These fundamentals include, but are not limited to, atmospheric circulation, humidity, residence times, recycling ratios, sources and sinks of atmospheric moisture, energy balance and climatic extremes.
- investigate the remote and local atmospheric feedbacks from human interventions such as irrigation and deforestation on the water cycle, precipitation and climate, based on observations and coupled modelling approaches.
- explore the implications of atmospheric feedbacks on the hydrologic cycle for land and water management. Can we favourably alter atmospheric hydrology and precipitation by means of ground based interventions of changing land cover, and thus changing evaporation, albedo and surface roughness?

The hydrological response to precipitation at the catchment scale is the result of the interplay between the space-time variability of precipitation, the catchment geomorphological / pedological / ecological characteristics and antecedent hydrological conditions. Therefore, (1) accurate measurement and prediction of the spatial and temporal distribution of precipitation over a catchment and (2) the efficient and appropriate description of the catchment properties are important issues in hydrology. This session focuses on the following aspects of the space-time variability of precipitation:
- Novel techniques for measuring liquid and solid precipitation at hydrologically relevant space and time scales, from in situ measurements to remote sensing techniques, and from ground-based devices to spaceborne platforms.
- Novel approaches to better identify, understand and simulate the dominant microphysical processes at work in liquid and solid precipitation.
- Applications of measured and/or modelled precipitation fields in catchment hydrological models for the purpose of process understanding or predicting hydrological response.

As the societal impacts of hazardous weather and other environmental pressures grow, the need for integrated predictions which can represent the numerous feedbacks and linkages between physical and chemical atmospheric processes is greater than ever. This has led to development of a new generation of high resolution multi-scale coupled prediction tools to represent the two-way interactions between aerosols, chemical composition, meteorological processes such as radiation and cloud microphysics.

Contributions are invited on different aspects of integrated model and data assimilation development, evaluation and understanding. A number of application areas of new integrated modelling developments are expected to be considered, including:

i) improved numerical weather prediction and chemical weather forecasting with feedbacks between aerosols, chemistry and meteorology,

ii) two-way interactions between atmospheric composition and climate variability.

This session aims to share experience and best practice in integrated prediction, including:

a) strategy and framework for online integrated meteorology-chemistry modelling;
b) progress on design and development of seamless coupled prediction systems;
c) improved parameterisation of weather-composition feedbacks;
d) data assimilation developments;
e) evaluation, validation, and applications of integrated systems.

This Section is organised in cooperation with the Copernicus Atmosphere Monitoring Service (CAMS), the "Pan-Eurasian Experiment" (PEEX) multidisciplinary program and the WMO Global Atmosphere Watch (GAW) Programme, celebrating its 30 years anniversary in 2019.

Data assimilation is becoming more important as a method to make predictions of Earth system states. Increasingly, coupled models for different compartments of the Earth system are used. This allows for making advantage of varieties of observations, in particular remotely sensed data, in different compartments. This session focuses on weakly and strongly coupled assimilation of in situ and remotely sensed measurement data across compartments of the Earth system. Examples are data assimilation for the atmosphere-ocean system, data assimilation for the atmosphere-land system and data assimilation for the land surface-subsurface system. Optimally exploiting observations in a compartment of the terrestrial system to update also states in other compartments of the terrestrial system still has strong methodological challenges. It is not yet clear that fully coupled approaches, where data are directly used to update states in other compartments, outperform weakly coupled approaches, where states in other compartments are only updated indirectly, through the action of the model equations. Coupled data assimilation allows to determine the value of different measurement types, and the additional value of measurements to update states across compartments. Another aspect of scientific interest for weakly or fully coupled data assimilation is the software engineering related to coupling a data assimilation framework to a physical model, in order to build a computationally efficient and flexible framework.

We welcome contributions on the development and applications of coupled data assimilation systems involving models for different compartments of the Earth system like atmosphere and/or ocean and/or sea ice and/or vegetation and/or soil and/or groundwater and/or surface water bodies. Contributions could for example focus on data value with implications for monitoring network design, parameter or bias estimation or software engineering aspects. In addition, case studies which include a precise evaluation of the data assimilation performance are of high interest for the session.

As the number of palaeoclimate data from glacial, marine, and continental archives is growing continuously, large-scale compilation and cross-comparison of these data is the imperative next phase in paleoclimate research. Large data sets require meticulous database management and new analysis methodologies to unlock their potential for revealing supra-regional and global trends in palaeoclimate conditions. The compilation of large scale datasets from proxy archives faces challenges related to record quality and data stewardship. This requires record screening and formulation of principles for quality check, as well as transparent communication.

This session aims to bring together contributions from paleoclimatic studies benefiting from the existence of such large data sets, e.g., providing a novel perspective on a proxy and the represented climate variables from the local to the global scale. We want to bridge the gap between data generation and modelling studies. In particular, comparing such large proxy-based datasets with climate modelling data is crucial for improving our understanding of palaeoclimate archives (e.g., bias effects and internal processes), to identify signal and noise components and their temporal dynamics, and to gain insight into the quality of model data comparisons.

We encourage submissions on data compilations, cross-comparison and modelling studies utilizing data repositories and databases (e.g., SISAL, PAGES2k, ACER, EPD), including, but not limited to:
-Comparative studies using one or several archives (e.g., including tests of temporal and spatial synchronicity of past regional to global climate changes)
-Proxy system models (and their tuning)
-Model data comparisons (including isotope enabled models or local calibration studies)
-Integrative multi-proxy/multi archive approaches at multiple study sites
-Large scale age model comparisons and record quality assessment studies, including methods aimed at cross validation between different records and variable spatial and temporal scales.

Changes in seasonal timing affect species and ecosystem response to environmental change. Observations of plant and animal phenology as well as remote sensing and modeling studies document complex interactions and raise many open questions.

We invite contributions with cross-disciplinary perspectives that address seasonality changes based on recent plant and animal phenological observations, pollen monitoring, historical documentary sources, or seasonality measurements using climate data, remote sensing, flux measurements or modeling studies. Contributions across all spatial and temporal scales are welcome that compare and integrate seasonality changes, study effects of long-term climate change or single extreme events, emphasize applications and phenology informed decision-making, discuss species interactions and decoupling, advance our understanding of how seasonality change affects carbon budgets and atmosphere/biosphere feedbacks, and integrate phenology into Earth System Models.

We emphasize phenology informed applications for decision-making and environmental assessment, public health, agriculture and forest management, mechanistic understanding of the phenological processes, and effects of changing phenology on biomass production and carbon budgets. We also welcome contributions addressing international collaboration and program-building initiatives including citizen science networks and data analyses.