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