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.

Data assimilation systems and numerical weather and climate models are essential to understand the current and past state of the Earth System, and to predict it's future. This session will summarize the latest progress in the development of such models including the assimilation of space-borne and conventional observations, developments for the numerical formulation of the models regarding both the fluid dynamic solver and physical parametrisation schemes, and developments towards weather and climate simulations at higher resolution on modern supercomputers.

Public information:
We will divide the session chats into smaller groups of 4 abstracts based on the order of abstracts in the session programme. Each group will have ~15 minutes. Each mini-session will be organized as follows:

- All authors post a few sentences to present their work.
- Everyone attending the mini-session can post questions or comments to the authors.
- All post related to one particular abstract should begin with the name of the first author. E.g. @David: What is the y-axis of Figure 2?

Forecasting the weather, in particular severe and extreme weather has always been the most important subject in meteorology. This session will focus on recent research and developments on forecasting techniques, in particular those designed for operations and impact oriented. Contributions related to nowcasting, meso-scale and convection permitting modelling, ensemble prediction techniques, and statistical post-processing are very welcome.
Topics may include:
 Nowcasting methods and systems, use of observations and weather analysis
 Mesoscale and convection permitting modelling
 Ensemble prediction techniques
 Ensemble-based products for severe/extreme weather forecasting
 Seamless deterministic and probabilistic forecast prediction
 Post-processing techniques, statistical methods in prediction
 Use of machine learning, data mining and other advanced analytical techniques
 Impact oriented weather forecasting
 Presentation of results from relevant international research projects of EU, WMO, and EUMETNET etc.

High-impact climate and weather events typically result from the interaction of multiple hazards across various spatial and temporal scales. These events, also known as Compound Events, often cause more severe socio-economic impacts than single-hazard events, rendering traditional univariate extreme event analyses and risk assessment techniques insufficient. It is therefore crucial to develop new methodologies that account for the possible interaction of multiple physical drivers when analysing high-impact events. Such an endeavour requires (i) a deeper understanding of the interplay of mechanisms causing Compound Events and (ii) an evaluation of the performance of climate/weather, statistical and impact models in representing Compound Events.

The European COST Action DAMOCLES coordinates these efforts by building a research network consisting of climate scientists, impact modellers, statisticians, and stakeholders. This session creates a platform for this network and acts as an introduction of the work related to DAMOCLES to the research community.

We invite papers studying all aspects of Compound Events, which might relate to (but are not limited to) the following topics:

Synthesis and Analysis: What are common features for different classes of Compound Events? Which climate variables need to be assessed jointly in order to address related impacts? How much is currently known about the dependence between these variables?
Stakeholders and science-user interface: Which events are most relevant for stakeholders? What are novel approaches to ensure continuous stakeholder engagement?
Impacts: What are the currently available sources of impact data? How can they be used to link observed impacts to climate and weather events?
Statistical approaches, model development and evaluation: What are possible novel statistical models that could be applied in the assessment of Compound Events?
Realistic model simulations of events: What are the physical mechanisms behind different types of Compound Events? What type of interactions result in the joint impact of the hazards that are involved in the event? How do these interactions influence risk assessment analyses?

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.

Wind and solar power are the predominant new sources of electrical power in recent years. Portugal’s renewable energy production in March 2018 was 104% of its electricity demand in the same month. 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. Planning and meteorology challenges in Smart Cities are common for both.

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.

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.

Mountains cover approximately one quarter of the total land surface on the planet, and a significant fraction of the world’s population lives in their vicinity. Orography critically affects weather and climate processes at all scales and, in connection with factors such as land-cover heterogeneity, is responsible for high spatial variability in mountain weather and climate.

Due to this high complexity, monitoring and modeling the atmosphere and the other components of the climate system in mountain regions is challenging both at short (meteorological) and long (climatological) time-scales. This session is devoted to the better understanding of weather and climate processes in mountain and high-elevation areas around the globe, as well as their modification induced by global environmental change.

We welcome contributions describing the influence of mountains on the atmosphere on meteorological time-scales, including terrain-induced airflow, orographic precipitation, land-atmosphere exchange over mountains, forecasting and predictability of mountain weather. Furthermore we invite studies that investigate climate processes and climate change in mountain areas and its impacts on dependent systems, based on monitoring and modeling activities. Particularly welcome are contributions that merge various sources of information and reach across disciplinary borders (atmospheric, hydrological, cryospheric, ecological and social sciences). In this respect the session invites also contributions on outcomes of the WMO "High Mountain Summit" taking place in October 2019.

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).

With the advent of the sub-seasonal to seasonal (S2S) prediction project, research communities now have 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 meteorological/oceanographic prediction in the 2 weeks to 2 months lead time range. The session will include both meteorological and impacts studies, that may use the S2S project’s database, but that can also use alternative sources of forecast information. Contributions are welcome for studies of phenomena such as the Madden Julian Oscillation (MJO), tropical/extratropical waves, stratospheric variability and stratosphere - troposphere coupling, in addition to studies of predictability/skill of atmospheric or surface variables and case studies of high impact weather events.

Contributions regarding impacts studies at the S2S time-range are also highly welcome, including, but not limited to, the areas of hydrology, health, fire, agriculture, and energy. These can include modeling studies of the impacts right through to presentations of how S2S-derived information can be integrated into decision support systems at the local, regional and country level.


******************* UPDATES********************************************************
Our two solicited speaker this year are:

Dr Adrian M Tompkins (ICTP,Italy) talking us about the potential to forecast malaria outbreaks at the S2S time scale.
Dr Suzana Camargo (columbia University, US) looking at the predictability of tropical cyclones at the S2S time scale

***************************************************************************************

The S2S dinner will take place as for tradition on the day of the session. You will receive an email with instruction if you would like to participate.

Public information:
S2S Session AS 1.9 Subseasonal-to-Seasonal Prediction: meteorology and impacts

Session 1: Monday 4 May 14:00-15:45 PM CET


14:00-15:15 Discussion/questions on individual displays

1. On the Resonances and Teleconnections of the North Atlantic and Madden-Julian Oscillations
Gilbert Brunet

2. Sub-seasonal prediction of the extreme weather conditions associated with the northeastern Australia floods in February 2019
Tim Cowan

3. Predictable weather regimes at the S2S time scale
Nicola Cortesi

4. The mutual impact of weather regimes and the stratospheric circulation on European surface weather
Christian Grams

5. Troposphere-Stratosphere Coupling In S2S Models and Its Importance for a Realistic Extratropical Response to the Madden-Julian Oscillation
Chen Schwartz

6. Impacts of ocean model resolution in S2S forecasts with the ECMWF coupled model
Chris Roberts

7. Convective-Permitting Modeling for Retrospective Subseasonal-to-Seasonal (S2S) Forecasting Using the Framework of the Coordinated Regional Ensemble Downscaling Experiment (CORDEX)
Hsin-I Chang

8. Tropical cyclone activity prediction on subseasonal time-scales
Suzana Camargo

9. Subseasonal forecasts for humanitarian decision-making in Kenya: understanding forecast skill and the latest results from the S2S ForPAc real-time pilot study.
Dave MacLeod

10. Forecasting climate extremes to aid decisions on multi-week timescales
Catherine de Burgh-Day

11. Understanding and forecasting the subseasonal meteorological drivers of the European electricity system in winter
Hannah Bloomfield

12. Sub-seasonal Monsoon Onset forecasting over West Africa
Elisabeth Thompson

13. Using a statistical model to verify warm conveyor belts in ECMWF’s sub-seasonal forecasts
Julian Quinting

14. Enhanced extended-range predictability of the 2018 late-winter Eurasian cold spell due to the stratosphere
Lisa-Ann Kautz

15. Promising subseasonal forecasting results based on machine learning
Matti Kämäräinen

15:15-15:45 General Discussion on S2S predictability/Modelling issues



Session 2: Monday 4 May 16:15-18:00 PM CET


16:15-17:30 Discussion/questions on individual displays


16. A new approach to subseasonal multi-model forecasting: Online prediction with expert advice
Paula Gonzalez

17. Heatwaves over Europe: Identification and connection to large-scale circulation
Emmanuel Rouges

18. Is Tuning of Auto-conversion Important for the Realistic Simulation of Indian Summer Monsoon Intraseasonal Oscillations and MJO in Coupled Climate Model?
Ushnanshu Dutta

19. Lagged ensemble vs burst sampling strategy for initializing sub-seasonal forecasts
Frederic Vitart

20. Sub-seasonal precipitation forecast skills over China during the boreal summer monsoon
Yuan Li

21. Quasi-Biweekly Oscillation over the tropical western Pacific in boreal winter： Its climate influences on North America
Zizhen Dong

22. The influence of aggregation and statistical post-processing on the sub-seasonal predictability of European temperatures
Chiem van Straaten

23. Flow-dependent sub-seasonal forecast skill for Atlantic-European weather regimes
Dominik Büeler

24. Jet Latitude Regimes and the Predictability of the North Atlantic Oscillation
Kristian Strommen

25. Relationship between meningitis occurrence and atmospheric conditions over the African meningitis belt
Cheikh Dione

26. Climate Advanced Forecasting of sub-seasonal Extremes (CAFE), ITN Project
Alvaro Corral


27. The potential predictability of Singapore and Maritime Continent weather regimes in relation to the MJO and ENSO
Mohammad Eeqmal Hassim

28. Subseasonal Forecasting of Aedes-borne Disease Transmission
Laurel DiSera

29. Quantifying the usefulness of European subseasonal forecasts using a real-world energy-sector framework
Joshua Dorrington

30 Teleconnection patterns in the Southern Hemisphere in subseasonal to seasonal models hindcasts and influences on South America
Iracema Cavalcanti

17:30-18:00 General Discussion on S2S prediction/applications

ENSO and its interactions with other tropical basins are the dominant source of interannual climate variability in the tropics and across the globe. Understanding the dynamics, predictability, and impacts of ENSO and tropical basins interactions, and anticipating their future changes are thus of vital importance for society. This session invites contributions regarding all aspects of ENSO and tropical basins interactions, including: dynamics, multi-scale interactions; low frequency, decadal and paleo variability; theoretical approaches; ENSO diversity; global teleconnections; impacts on climate, society and ecosystems; seasonal forecasting and climate change projections of ENSO and its tropical basins interactions. Studies aimed at understanding ENSO and its tropical basins interactions in models of a range of complexity are especially welcomed, including analysis of CMIP model intercomparisons.

Please note that this session will be linked to a special session for the presentation of the Fridtjof Nansen Medal. We also have Daniela Domeisen and Caroline Katsman as invited speakers.

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
-- 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
-- response of the atmosphere to changes in the North Atlantic
-- 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

Recent extreme weather and climate episodes, including the European heatwaves of summer 2003 and June/July 2019, highlight the need to further our understanding of linear and non-linear (quasi-stationary) planetary and synoptic-scale Rossby wave dynamics in the atmosphere, and their impacts on weather and climate events. Abstracts are solicited that are dedicated to:
i) the dynamics of linear wave propagation or quasi-stationarity, of wave breaking, atmospheric blocking, or jets as atmospheric Rossby waveguides. This includes the role of local and remote drivers (e.g., the tropics, Arctic, or stratosphere).
ii) exploring the links between extreme weather/climate events and linear and non-linear Rossby waves, including wave breaking and/or blocking.
iii) quantifying model representation of Rossby waves in climate and numerical weather prediction models, including wave propagation and breaking.
iv) exploring the role of Rossby wave trains on predictability at lead times from medium range (~2 weeks) to seasonal time-scales. This includes blocking and wave propagation.
v) analyzing projected future changes in planetary or synoptic-scale Rossby waves, or in their future impacts on weather and climate events.

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 as well as undergoing climate variability on subseasonal, interannual and decadal 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 on temporal scales from numerical weather prediction (NWP), subseasonal-to-seasonal and interannual-to-decadal predictions, and longer timescale climate projections. A better understanding of monsoon physics and dynamics, with more accurate simulation, prediction and projection of monsoon systems is therefore of a great importance to society.

The combination of modern- and palaeo-monsoon research can help us 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. Theoretical works based on idealized planetary and ITCZ frameworks are also invited.

Public information:
10:45 Welcome
10:50 Arvind Singh: Increase in summer monsoon rains in northeast India during ENSO periods: a multiproxy analysis
10:58 Michael Byrne: Radiative effects of clouds and water vapour on the monsoon
11:06 Feng Shi: A reconstruction of the East Asian summer monsoon index over the past half millennium
11:14 Marcia Zilli Synoptic climatology and changes in precipitation associated with the SACZ using a cloud band identification technique
11:22 Qiaoling Ren: Effects of the Tibetan Plateau on East Asian Summer Monsoon via Weakened Transient Eddies
11:30 Tresa Mary Thomas: Statistics of Monsoon Low Pressure Systems in the Indian Subcontinent and Estimation of Related Extreme Rainfall Risk
11:38 Junbin Wang: Is the Current Subtropical Position of the Tibetan Plateau Optimal for Intensifying the Asian Monsoon?
11:46 Kyung-Ja Ha: Future changes of summer monsoon characteristics and evaporative demand over Asia in CMIP6 simulations
11:54 Marco Gaetani: Role of friction and orography in the Asian-African monsoonal system
12:02 Nitin Babu George: Abrupt transition in organized convection during the monsoon onset in central India and Climate change effect
12:10 Xin-Gang Dai: A climate classification: Mediterranean, monsoon and westerlies
climates
12:18 Lun Dai: Classification and Diagnosis of Summer Monsoon Rainfall Patterns and their Potential Predictability in Southeast China

As a weather pattern, the Asian monsoon impacts the lives of more than a billion people. With rapid population and economic growth across the monsoon region, it becomes a pressing concern that the convection coupled to surface emissions is playing a significant role in the region’s air quality. The uplift of pollutants also enhances aerosol–cloud interactions that may change the behaviour of the monsoon. The monsoon system is therefore relevant to scales and processes bridging regional air quality, climate change, and global
chemistry-climate interaction and the chemical transport effect of the monsoon system is seen from satellites as an effective transport path for pollutants to enter the stratosphere.
The session will focus on the dynamical, micro-physical, and chemical processes dominating transport, chemical transformations and particle and cloud formation throughout the Upper-Troposphere Lower-Stratosphere above the Asian Monsoon system as well their internal and ozone and climate couplings. Here we especially encourage experimental and modelling (process to global) studies from recent programmes (such as StratoClim, BATAL, OMO). Contributions addressing tropospheric processes within the Atmospheric Composition and Asian Monsoon (ACAM) Programme objectives, such as the coupling to local emission on air quality and aerosols, clouds, interactions with the Asian monsoon are also welcome.

Public information:
The session goes from 12h30 with anticipation of a group of papers
and is supported by a live video / audio session (https://talk.icg.kfa-juelich.de/b/str-cr4-27w)

Virtual video session: 12:30-14:00 – Paper block #1
https://talk.icg.kfa-juelich.de/b/str-cr4-27w - please keep your mic muted and video off -
The link will be active 30 minutes before the session time
@all: make use of the live chat for questions
Please keep your mic muted and video off
9’ presentation + 1’ for one eventual question

EGU Live chat: 14:00-15:30 Discussion block #1 & Paper block #2
@all: make use of the live chat for questions
(https://egu2020.eu/sharing_geoscience_online/how_to_use_the_chats.html)
5' for each paper of block #1
3’ to present/summarize with reference to the displays + 5’ minutes for the questions for block #2

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. Besides, this year we welcome abstracts reporting results on the SouthTRAC campaign in the Southern Hemisphere, as well as any other major collaborative projects such as MS-GWaves.

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.

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.

This session investigates mid-latitude cyclones and storms on both hemispheres. We invite studies considering cyclones in different stages of their life cycles from the initial development, to large- and synoptic-scale conditions influencing their growth to a severe storm, up to their dissipation and related socioeconomic impacts.
Papers are welcome, which focus also on the diagnostic of observed past and recent trends, as well as on future storm development under changed climate conditions. This will include storm predictability studies on different scales. Finally, the session will also invite studies investigating impacts related to storms: Papers are welcome dealing with vulnerability, diagnostics of sensitive social and infrastructural categories and affected areas of risk for property damages. Which risk transfer mechanisms are currently used, depending on insured and economic losses? Which mechanisms (e.g. new reinsurance products) are already implemented or will be developed in order to adapt to future loss expectations?

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 Speakers:
Nicolas Bellouin (University of Reading)
Anna Possner (Goethe University Frankfurt)

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. This year we will have a special emphasis on convective organization. Studies that investigate the organization of convection, being in idealized set-ups (radiative convective equilibrium and self-aggregation) or in observations, as well as studies that investigate the importance of organization for climate are particularly welcome. Besides this, studies that investigate general aspects of convection such as processes controlling the lifecycle of convection, interactions of convection with other physical processes and representation of convection in numerical weather prediction and climate models are also welcome.

The uncertain response of clouds to global warming is a major contributor to the spread in climate sensitivity across climate models. Cloud feedback uncertainty is related to a limited understanding of the coupling between clouds, convection and the large-scale circulation. This session focuses on efforts to advance our understanding of the cloud-circulation coupling and its role in climate change. Contributions from dedicated field campaigns such as EUREC4A, from various observing platforms like ground-based and satellite remote sensing or in situ measurements, as well as modelling and theoretical studies are welcomed. We also invite abstracts focusing on the role of convective organization and precipitation in modulating the cloud-circulation coupling and cloud feedbacks.

Precipitation is an essential aspect of climate, and also drives many climate impacts. The primary tool for projecting future precipitation is climate models. Climate models are already being used, both directly and indirectly, to quantify anticipated impacts of climate for the purpose of making decisions. Improving precipitation in models requires (1) quantifying characteristics of precipitation in relevant observational datasets, (2) comprehensive comparison of climate model precipitation against observations, and (3) sustained model development efforts focus on improving precipitation in models. It also requires addressing the many characteristics of precipitation, ranging from its mean spatial pattern through its variability across timescales from hourly and diurnal extending through extreme events (whether dry or wet).

We invite presentations in this session that address:
- metrics to quantify the characteristics of precipitation in observations,
- evaluation of climate model simulations against observations, and
- development efforts aimed at improving precipitation in models (including seamless modeling systems).

This session explores advances and challenges in convection-permitting atmospheric modelling: 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 research area and improve both the diurnal convective cycle and the representation of convective precipitation, particularly extremes. CPMs often exhibit important differences in feedback mechanisms and climate change signals compared to coarser models. CPMs thus offer a promising tool to better understand fine-scale processes and provide critical information to end users, especially in areas affected by convective extremes, and have thus sparked wider interest in their applications and development. For example, the CORDEX-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 uncertainty at convective scale
-- Physical understanding of added value over coarser models
-- Land-atmosphere coupling at convection-permitting scale
-- Climate studies
-- Tropical phenomena
-- Convection, energy balance and hydrological cycle
-- Lightning in CPMs
-- Teleconnection across scales
-- Novel high-resolution experiments

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.

In recent years, attention was paid to the detection and monitoring of volcanic ash clouds as their impact on the air traffic control system was unprecedented. Volcanic clouds are dangerous for the aviation 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.
The intensity of the extreme convective events is supposed to increase worldwide due to the climate change and they can also cause large damages and affect air safety.

The recent Anak Krakatau, Raikoke and Ulawun eruptions highlighted the issue on different techniques to distinguish volcanic ash clouds from convective clouds, and the unsolved problem to understand if the cloud top is tropospheric or stratospheric.

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. 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.

This session solicits the latest studies from the spectrum of:
- Volcanic and Convective Clouds (CVC) remote sensing, detection, monitoring, modeling, forecasting and nowcasting
- understanding of CVC structure, including overshooting and ice clouds
- understanding the impact of CVC on climate changes and air safety
- proposal of new products or services focused on the end-users prospective (air traffic management and air safety)
- discussion on the recent Anak Krakatau, Raikoke and Ulawun eruptions

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.

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 Lightning-produced NOx
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 electrical phenomena on other planets
Lightning, tropical storms and climate
Modeling of thunderstorms and lightning
Now-casting and forecasting of thunderstorms
Laboratory investigation of lightning discharge physics processes

Ice and mixed-phase clouds largely contribute to the Earth’s radiation budget because of their high temporal and spatial coverage. Yet, the variability and complexity of their macro- and microphysical properties - consequence of intricate ice particle nucleation and growth processes - makes their study extremely challenging. As a result, large uncertainties still exist of our understanding of ice cloud processes, radiative effects and interactions with their environment (in particular, aerosols).

This session aims to advance our comprehension of ice clouds by bringing observation- and modelling-based research together. A PICO format is selected to further encourage exchanges between the communities.

A diversity of research topics shall be covered, highlighting recent advances in ice cloud observation techniques, modelling and subsequent process studies:

(1) Ice cloud observations from airborne, spaceborne, ground- or laboratory-based measurements and their derived products (retrievals), which are useful to understand process details, formation mechanisms and provide climatology.

(2) Model simulations (process-based, regional and global) on the other hand allow putting the detailed observations in a wider perspective, providing additional insights in the formation mechanisms and allowing for future predictions.

Both approches brought together can uniquely answer question regarding dynamical influence on ice cloud formation, life cycle, coverage, microphysical and radiative properties, crystal shapes, sizes and variability of ice particles in mixed-phase as well as ice clouds. Joint observation-modelling contributions are therefore particularly encouraged.

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

This joint session invites papers that are related to the mesosphere and lower thermosphere. It addresses the topical fields of the VarSITI (Variability of the Sun and Its Terrestrial Impact) program initiated by SCOSTEP, focusing on the role of the sun and the middle atmosphere/thermosphere/ionosphere in climate (ROSMIC). Contributions studying radiation, chemistry, energy balance, atmospheric tides, planetary waves, gravity waves, neutral-ion coupling, and the interaction of the various processes involved are welcome.
This includes work on model data as well as measurements from satellites and ground based platforms such as ALOMAR.

With the launch of the unique Aeolus wind profiling mission, new perspectives on atmospheric dynamics are being revealed to benefit a number of prospective applications. For example, improvements in Numerical Weather Prediction (NWP), General Circulation Models (GCMs) and their included parameterized processes, such as land and ocean drag, convection, stratosphere-troposphere interaction and atmospheric waves. In this session, we aim at discussing the new data products and their validation, as well as studies using the Aeolus data for application in meteorology. Topics may vary from observation interpretation, GCM or NWP model diagnostics, parameterization and data assimilation experiments. We welcome all presentations based on Aeolus mission data, including inter-comparisons of different remote sensing measurements dedicated to wind profiling, clouds or aerosol, and/or using analyses with ground-based measurements and GCMs. This includes also studies on the optical properties as measured by Aeolus and their use for clouds and aerosol studies.

Public information:
The text chat session will follow the AS1.35 session list, distributing available time over all uploaded presentations. Authors, please prepare a 1-2 sentence summary in advance, which you can paste in when your display is called up for discussion. Participants, please prepare your brief questions for pasting into the text chat session. Looking forward to an animated session!

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.

The AMANOM session will focus on observations related to contrails, fog, clouds, precipitation, and short range forecasting of weather conditions associated with aviation operations. Abstracts for all areas of aviation meteorology, including Polar regions, high altitude conditions, as well as airport environments, can be submitted to this session. Work on aviation meteorology parameters such as visibility, icing, gusts and turbulence, as well as fog and precipitation, will be considered for this session. Topics related to In-situ observations obtained from aircraft, Unmanned Aerial Vehicles (UAVs), and supersites, remote sensing retrievals of meteorological parameters from satellites, radars, lidars, and MicroWave Radiometers (MWRs), as well as other emerging technological platforms, and predictions of meteorological parameters from the numerical weather prediction models will be considered highly related to the goals of this session.

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:
- "Observing the surface radiation and energy balance, carbon dioxide and methane fluxes over the city centre of Amsterdam", by Dr. Gert-Jan Steeneveld, Wageningen University, The Netherlands.

Changes in the Arctic and Antarctic climate systems are strongly related to processes in the boundary layer and their feedbacks with the free troposphere, ocean and ice. An adequate understanding and quantification of these processes is necessary to improve predictions of future changes in the polar regions and their teleconnection with mid-latitude weather and climate, including meridional transport of heat, moisture and chemical constituents. Processes include atmosphere-ocean-ice (AOI) interactions, physical and chemical snow processes (e.g. snow photochemistry), exchange of chemical constituents including biogeochemical impacts , sources of aerosol, polynya formation processes, sea ice production and loss, 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 extreme events such as warm air advection and clouds on the surface energy budget and related boundary layer exchanges. 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, transport and atmospheric chemical processing of pollution, especially under cold and dark conditions, are poorly understood. Similarly, the polar boundary layer can involve complicated radiative processes such as shallow stable layers with fog present. In addition, polar boundary layers can mediate chemical, aerosol, and isotope exchanges between the atmosphere and the firn important to the interpretation of ice core records.
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 also encourage preliminary results from field programs such as MOSAiC and other high-latitude research efforts.

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-turbulence interactions, 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.

Geophysical Fluid Dynamics (GFD) is a truly interdisciplinary field, including different topics dealing with rotating stratified fluids. It emerges in the late 50s, when scientists from meteorology, oceanography, astrophysics, geological fluid dynamics, and applied mathematics began to mathematically model complex flows and thereby unify these fields. Since then many new aspects were added and deeper insight into many problems has been achieved. New mathematical and statistical tools were developed, standard techniques were refined, classical problems were varied. In this session we primarily focus on contributions from dynamic meteorology and physical oceanography that model flows by mathematical analysis. However, it is also a forum for experimental GFD and for astrophysical and geological aspects of GFD as well.

Land-atmospheric interaction includes the land surface and atmospheric states and the mass and energy exchanges between land surface and the atmosphere. It is a key part of the Earth's weather and climate system. Studies of the land-atmosphere interaction are critical to the understanding of the Earth’s weather and climate system that is required for accurate weather and climate forecasts. These studies mainly involve ground observations, air-borne or space based remote sensing of land surface and the lower atmosphere properties, mass and energy fluxes and their dynamics, and numerical model simulations of the land-atmosphere processes. Since the 1970s, a large number of field observation experiments (such as FIFE, HAPEX/Sahel, HAPEX/MOBILHY, EFEDA, BOREAS, NOPEX, GAME, HEIFE, TIPEX, EAGLE, CAMP/Tibet, TPE and LOPEXs) have been or are currently being carried out over a wide range of different underlying land surfaces worldwide. Dozens of land process parameterization schemes or land surface models have been developed and refined. Major national and international agencies (e.g. NASA, NOAA, ESA, EUMETSAT, JAXA, CMA, JMA, KMA, etc.) have launched many satellite missions to provide continuous spatially distributed observations of land surface and atmospheric observations from local scale to regional and even global scales. Examples of these missions are EOS, Meteosat, EPS, GCOM-W, GOES, S-NPP, JPSS, FYs, SMOS, SMAP, etc. Assimilation of these observations have significantly improved understanding of the land-atmosphere interaction and in turn gradually enhanced the prediction skills of the simulation models at all of these scales. This session invites abstracts that report the development, validation and applications of these studies especially in the Third Pole Environment regions in the recent years. New development on land surface process observation, data fusion, data assimilation, hydrological hazards monitoring, climate and environmental changes at regional and global scales are especially encouraged.

Land–atmosphere interactions often play a decisive role in shaping climate extremes. As climate change continues to exacerbate the occurrence of extreme events, a key challenge is to unravel how land states regulate the occurrence of droughts, heatwaves, intense precipitation and other extreme events. This session focuses on how natural and managed land surface conditions (e.g., soil moisture, soil temperature, vegetation state, surface albedo, snow or frozen soil) interact with other components of the climate system – via water, heat and carbon exchanges – and how these interactions affect the state and evolution of the atmospheric boundary layer. Moreover, emphasis is placed on the role of these interactions in alleviating or aggravating the occurrence and impacts of extreme events. We welcome studies using field measurements, remote sensing observations, theory and modelling to analyse this interplay under past, present and/or future climates and at scales ranging from local to global but with emphasis on larger scales.

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 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)
- Impacts 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, ACE and other campaigns in the Arctic and Southern Ocean/Antarctica, and encourage related contributions.

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


Public information:
Dear Authors,

Thank you all for your great contributions to this session. Hopefully, you have all already successfully uploaded your display material - if not please try to do it on Tuesday (before the Live Chat). If this is not possible - you can do it also during this month. Everyone in any case is welcome to participate in the Live Chat to share their work.

We invite everyone to check the posted material before our session's Live Chat, which is scheduled on 6 May, 08:30–10:15 (CEST=UTC+2). The Live Chat will be open from 8:15 to 10:45 CEST and is only by text chatting.

During the Live Chat we (conveners) will call the authors in the order of the Displays (which will be visible on the right from the chat's window) to shortly introduce their work (motivation.. main points..). It will be easier if everyone has this SHORT text prepared before hand. Please avoid copy/pasting the entire abstract, as all session participants have had the possibility to read the abstract and the posted material prior to the chat session. Then the chat will be open for questions and comments from all participants (we also recommend if possible to prepare your questions beforehand). With 21 abstracts we will have about 5 min to discuss each display.

If there are authors who are certainly not available to be present during the Live Chat - please let us know. You are also welcome to ask your co-authors or colleagues to present your work if the main author is not available at the chat time.

The Chat will be not recorded or stored. Only abstracts and displays will be available after this session. Everyone is welcome to post their comments directly to the Displays (commenting will be open until 1 June). This provides more freedom to discuss.

Looking forward to this new way of science sharing! Hope it goes smoothly:)

Best wishes to you all

Irina, Susanne, Manfred, Tom, Nicole

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 cyclones, 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.

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 include 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.

We invite presentations on ocean surface waves, and wind-generated waves in particular, their dynamics, modelling and applications. This is 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

This session aims at fostering discussions on the physical processes at work at the air-sea interface, including their observation and their representation in coupled numerical models. Examples of such processes are solar radiation-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. Air-sea interaction related to surface temperature and salinity fronts, as well as 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, water, momentum, gas and aerosols 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 field campaigns or 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.

Observations and model simulation illustrate significant ocean variability and associated air-sea interactions from regional to global scale and on diurnal to inter-annual time scales. This session is devoted to the understanding of the tropical and subtropical ocean dynamics, its interaction with the overlying atmosphere from the equator to mid-latitudes and its climate impacts on adjacent to remote areas.
Relevant processes in the ocean include upper and deep ocean circulation, mild SST gradients to sharp fronts, eddies, filaments, tropical instability waves, warm pools, cold tongues and eastern boundary upwellings. Furthermore, we are interested in air-sea interactions related to both the seasonal cycle and the development of modes of variability from local to basin scale. Wind variations related to Madden-Julian Oscillation, cyclones, and convective systems, as well as those leading the air-sea coupled modes (e.g., the Meridional Mode and Atlantic Niño) are welcome. Finally, we also seek contributions examining the causes and impacts of systematic model errors in simulating the local to regional climate.
Studies based on direct observations, reanalysis, reconstructions as well as model simulations are welcome.

Over the past decades, emission reductions for air pollution abatement resulted in changes in precipitation, cloud and aerosol chemical composition, and in atmospheric deposition of anthropogenically derived nutrients to the ocean, affecting atmospheric acidity and atmospheric deposition to ecosystems.
Atmospheric acidity is central to many processes in the atmosphere and the Earth system: atmospheric chemistry, biogeochemical cycles, atmospheric deposition, ecosystems, human health, and climate. Atmospheric deposition impacts on marine productivity, oceanic carbon dioxide uptake and emissions to the atmosphere of climate active species. These oceanic emissions of reactive species and greenhouse gases influence atmospheric chemistry and global climate, and induce potentially important chemistry-climate feedbacks. Thus, air-sea fluxes of biogeochemically active constituents have significant impacts on global biogeochemistry and climate.
Despite the wide range of important effects of atmospheric acidity and air-sea exchanges, scientific knowledge gaps remain. Understanding atmospheric acidity’s levels, its spatial and temporal variability and controlling factors in the precipitation and the suspended atmospheric media, aerosols and clouds, and its multiple impacts, is an open scientific topic for research. We also still lack understanding of many of the physical and biogeochemical processes linking atmospheric deposition, atmospheric acidity, 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.
To address these current knowledge gaps, in this session we welcome new findings from laboratory, in-situ and remote sensing observations and atmospheric and oceanic numerical models, on the status of atmospheric acidity, the factors that affect its levels, its wide range of impacts, on atmospheric deposition of nutrients and toxic substances to the ocean, their impacts on ocean biogeochemistry, on the air-sea fluxes of climate active species and potential feedbacks to climate.
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).

Earth Systems Models aim at describing the full water- and energy cycles, i.e. from the deep ocean or groundwater across the sea or land surface to the top of the atmosphere. The objective of the session is to create a valuable opportunity for interdisciplinary exchange of ideas and experiences among members of the Earth System modeling community and especially atmospheric-hydrological modelers.
Contributions are invited dealing with approaches how to capture the complex fluxes and interactions between surface water, groundwater, land surface processes, oceans and regional climate. This includes the development and application of one-way or fully-coupled hydrometeorological prediction systems for e.g. floods, droughts and water resources at various scales. We are interested in model systems that make use of innovative upscaling and downscaling schemes for predictions across various spatial- and temporal scales. Contributions on novel one-way and fully-coupled modeling systems and combined dynamical-statistical approaches are encouraged. A particular focus of the session is on weakly and strongly coupled data assimilation across the different compartments of the Earth system for the improved prediction of states and fluxes of water and energy. Merging of different observation types and observations at different length scales is addressed as well as different data assimilation approaches for the atmosphere-land system, the land surface-subsurface system and the atmosphere-ocean system. The value of different measurement types for the predictions of states and fluxes, and the additional value of measurements to update states across compartments is of high interest to the session. We also encourage contributions on use of field experiments and testbeds equipped with complex sensors and measurement systems allowing compartment-crossing and multi-variable validation of Earth System Models.

To showcase their strong thematic connection, the two sessions “Air-Land Interactions (General Session)” and “Understanding and Characterization of Land-Atmosphere Feedback” were merged.

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.

The understanding of feedback processes in the land-atmosphere (L-A) system is crucial for advanced modeling and prediction of weather and climate. However, the impact of soil moisture and evapotranspiration on the diurnal cycle of the planetary boundary layer (PBL), clouds, and precipitation remains a sore gap in our understanding of weather processes and climate statistics. For this purpose, the exchange of momentum, water, energy, and carbon at the land surface and at the top of the PBL has to be investigated from the local to regional scales in great detail. In this session, 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 for studying L-A exchange processes and entrainment at the PBL top based on long-term data sets or recent field campaigns, e.g., combining multi-tower, scanning lidar, airborne, and satellite observations. With respect to theoretical understanding and modeling, we welcome the study of feedback processes as well as the derivation and application of feedback metrics from the mesoscale to turbulent scales, e.g., derived by large eddy simulations.

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 surface phenomena. Aerosol surface characteristics and heterogeneous reactions on aerosol surfaces impact they formation and atmospheric lifetime, and are also associated with adverse health effects. In addition, processes in aqueous aerosol surfaces are shown to significantly affect the cloud droplet activation. Despite of potentially important role of aerosol surfaces in atmospheric process, there are still very limited selection of methods that can be applied to study the surface characteristics and processes. With this in mind, aside from general submissions on aerosol research, we encourage contributions from work within the broad focus of aerosol surface phenomena. These might include work on:
* Molecular scale investigations, from single component to complex mixtures
* Evidence from laboratory and field studies
* New experimental capabilities
* New modelling capabilities
* Impact studies

The session focuses on the variability of the tropospheric and stratospheric chemical composition on the timescales from diurnal to decadal. It discusses the processes driving this variability and attribution of changes. 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 chemical composition of the middle atmosphere is not only relevant for understanding radiative forcing or protection of the biosphere from harmful UV radiation, but it also has an influence on tropospheric circulation and dynamics that act as a feedback on climate. Increasing greenhouse gases are expected to modify the large-scale circulation of the stratosphere, termed Brewer-Dobson circulation (BDC), and the chemical compositions of radiatively active gases, notably ozone and water vapour, in the upper troposphere and lower stratosphere (UTLS) region. Such changes in the BDC and UTLS composition are expected to change levels of surface UV radiation, modify the radiative forcing of climate, and feedback on the dynamics both within the stratosphere and at the surface. This session is particularly interested in evidence of the direct influence of climate change upon stratospheric dynamics and chemistry, as well as indirect feedbacks from these changes back upon surface climate. We welcome abstracts focused on stratospheric composition changes on time-scales encompassing inter-annual to centennial timescales,on local to global spatial scales, future projections from chemistry climate models, and discussing changes induced by both natural and anthropogenic factors, observations, as well as theoretical studies.

This session examines the variability of trace gases and aerosols in the troposphere,
and how the chemical heterogeneity challenges our ability to compare models and measurements. Papers will examine how transport, chemicophysical processes, and emissions can create the chemical patterns we observe, and how different modeling approaches (Lagrangian and Eulerian) are able to establish and sustain them. Resolved advective transport (e.g., jet streams, frontal systems) as well as convection, turbulence, precipitation and scavenging, create a mixture of chemically distinct air masses. We will examine how this heterogeneity can be observed and assessed in models. Even over the remote ocean basins we find a mixture of anthropogenic pollution mixed with the chemistry of the marine boundary layer. Pollution or land-based signatures are useful in tracing the history of air parcels, but it remains uncertain whether this diluted pollution can influence the chemical reactivity.
In addition, we look for observations and models that can evaluate the chemical patterns in terms of which combinations, or covariation of key species, makes some air parcels more reactive than others, and thus controls the evolution of tropospheric ozone and methane. Likewise, we look for observations and modeling techniques that help us understand how aerosols are modified by atmospheric processes, from generation of new particles to removal by precipitation. A fundamental evaluation of our current chemistry-climate models can be based on matching this heterogeneity.

The composition of the upper troposphere and the stratosphere (UTS) plays a key role in the climate system. Our understanding of the interactions between dynamics, chemistry and climate in this region has been rapidly increasing over the last years thanks to combined observational and model based studies. In this session we invite studies of dynamical, transport and chemical processes determining the variability at all scales and long-term trends in the composition of the UTS. We particularly encourage studies bringing together recent in-situ and/or remote sensing observations and model simulations.

A better understanding of the role of natural aerosols in the atmosphere is essential for assessing anthropogenic radiative forcing and the climate response. Our session explores primary aerosols and those formed from precursor gases emitted by natural sources, e.g. from wildfires, deserts, volcanoes and both the marine and terrestrial biosphere. The session intends to bring together experts from different fields to assess the state-of-the-science knowledge on natural aerosols and to identify future directions to reduce uncertainty. We encourage submissions that use models across different spatial scales and consider past, present or future perspectives, as well as measurements from remote sensing, field campaigns and laboratory experiments. Questions of particular interest are, but are not limited to: 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 and deposition changed over time? What are the consequences of these changes? Where are the missing links in our understanding of 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?

The interactions between aerosols, climate, and weather are among the large uncertainties of current atmospheric research. Mineral dust is an important natural source of aerosol with significant implications on radiation, cloud microphysics, atmospheric chemistry and the carbon cycle via the fertilization of marine and terrestrial ecosystems.
In addition, properties of dust deposited in sediments and ice cores are important (paleo-)climate indicators.

This interdivision session is open to contributions dealing with:
(1) measurements of all aspects of the dust cycle (emission, transport, deposition, size distribution, particle characteristics) with in situ and remote sensing techniques,
(2) numerical simulations of dust on global and regional scales,
(3) meteorological conditions for dust storms, dust transport and deposition,
(4) interactions of dust with clouds and radiation,
(5) influence of dust on atmospheric chemistry,
(6) fertilization of ecosystems through dust deposition,
(7) any study using dust as a (paleo-)climate indicator including investigations of Loess, ice cores, lake sediments, ocean sediments and dunes.

We especially encourage to submit papers on the integration of different disciplines and/or modeling of past, present and future climates.

Public information:
Please be aware that there are a number (N=3) changes in the order in which the presentations will be discussed. Please have a look at the provided session materials for the final program.

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, 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, shape, and surface properties makes it difficult to understand and parameterize their microphysical and hence radiative properties.
Fundamental understanding of the cloud dynamics and aerosol properties, which play the major role in the climate system, will require the understanding of gas-, water-, and ice-aerosol surface interactions. To advance our knowledge about atmospheric processes, this session aims to bring together two research areas, namely (1) Atmospheric Surface Science (ASS) and (2) Ice particles (IP) and Ice Nucleating Particles (INP):
(1) ASS is concerned with the experimental and theoretical approaches investigating atmospheric interactions as well as ice nucleation processes “on the molecular level”. The goal is to fill the gap between the large scale atmospheric processes and gas-, water-, and ice- interactions with atmospherically relevant mineral and biological surfaces.
(2) IP and INP are concerned with the laboratory examination, on a fundamental level, trying to understand the nucleation processes and characterizing IP and INP in the atmosphere.

- Solicited talk_1: "The Portable Ice Nucleation Experiment chamber (PINE): laboratory characterization and field test for its semi-automated ice-nucleating particle measurements in the Southern Great Plains".
Speaker: Naruki Hiranuma, West Texas A&M University, USA.

This symposium seeks to bring together environmental and atmospheric photochemists to help bridge the topics of aquatic photochemistry and aerosol photochemistry. The field of aquatic photochemistry seeks to understand the photochemical properties of dissolved organic matter which lead to the degradation of pollutants, particularly in the context of water treatment. On the other hand, the field of aerosol photochemistry seeks to understand the properties of the organic fraction in atmospheric aerosol capable of impacting climate through aerosol-radiation and aerosol-cloud interactions. Both fields have similar goals of characterizing the response of organic matter whether it be in lakes, rivers and oceans or in the atmosphere to sunlight exposure. This symposium will facilitate these two fields coming together to share techniques, sampling protocols and chemical insights. The symposium will gather field and laboratory researchers, environmental engineers, aerosol scientists, and atmospheric chemistry modelers with the goal of discussing emerging research in photochemistry of organic matter both in the aquatic and aerosol phases.

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".

Public information:
Session invited talk (live presentations on Zoom Meetings):

Mon, 04 May, 14:00-15:45 (Vienna Time)

14:00-14:35 Markku Kulmala, Reducing urban new particle formation as a plausible solution to
mitigate particulate air pollution in Beijing and other Chinese megacities
14:35-15:10 Gregory Carmichael, Aerosol Chemistry and Effects in the Anthropocene
15:10-15:45 Meng Gao, Aerosol Pollution in Asia and Its Interactions with Climate

Join Zoom Meeting: https://zoom.us/j/8425924612
Meeting ID: 842 592 4612
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The gas-phase oxidation of organic compounds leads to the formation of less volatile organic compounds that may condense on aerosol surfaces. One key aspect of the transformation of organic species is the fate of organic peroxy radicals that are formed after the initial radical attack. This session aims for contributions connecting the gas-phase oxidation of organic compounds with the formation of secondary organic aerosol. Oxidation agents can be the hydroxyl radical, ozone or the nitrate radical. We invite contributions on the investigation of the gas-phase chemistry leading to secondary organic aerosol or on the investigation of aerosol properties as a consequence of the oxidation process. Contributions can include the development and test of mechanisms describing the chemical transformation of organic compounds in laboratory and in experiments in simulation chambers as well as insights from field studies.

Methane is an important greenhouse gas that has contributed ∼25% of the radiative forcing experienced to date. Despite methane’s short atmospheric lifetime (~10 years), global methane concentrations have grown more than three times faster than carbon dioxide since the industrial revolution. This makes methane emission mitigation an effective way to reduce the short-term rate of warming. In contrast to carbon dioxide, anthropogenic methane emissions originate from a large variety and number of diffuse point sources that are mostly independent of combustion processes. As a result, systematic atmospheric measurements are needed to inform emission inventories and mitigation strategies.

This session will highlight research that focuses on methane emissions from human activities (e.g., fossil fuel infrastructure, fire, rice production, ruminants, landfills and waste). Particular emphasis is on studies collecting atmospheric observations at different spatio-temporal scales with the aim to (1) reduce the uncertainty in the measured magnitude of emissions, (2) identify source-specific emission patterns and mitigation opportunities, and (3) inform stakeholders, such as regulators and industry representatives, on mitigation pathways.

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-3, GOSAT-2, Sentinel 5P, CO2M), as well as ground-based (e.g., TCCON, COCCON), aircraft, other remote sensing instruments. This includes, e.g., advances in retrieval techniques, instrumental concepts, and validation activities, but we specifically encourage contributions that focus on the interpretation of observations in respect to natural fluxes or anthropogenic emissions.

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.

Public information:
Based on the outcome of a poll among the presenting authors, the live chat of this session has been cancelled.

A subset of the presentations will be given in a video session on Wednesday, 27nd of May. If you are interested to join, please contact the convenors for details.

We are sorry that we cannot have a live EGU session this year and hope to see you all again in Vienna next year!

Andreas Richter, Anja Schönhardt, Cathy Clerbaux, Pieternel Levelt

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 will also showcase the new projects and efforts to develop “good-practice” standards under the World Meteorological Organization (WMO) Integrated Global Greenhouse Gas Information System (IG3IS), which is part of WMO’s commitment to science-based services.

High surface ozone concentrations are of major concern in many regions of the world. Despite major efforts to reduce emissions, some areas (e.g Asia) regularly experience a large number of ozone pollution events in the summer. In addition, high ozone formation rates have also been observed in wintertime. Photochemical transformation of organic compounds in the presence of nitrogen oxides is responsible for ozone production. Due to the strong dependence of ozone production on nitric oxide concentrations, emission reduction of nitrogen oxides affects also ozone concentrations in the troposphere. The session aims for contributions reporting observations of ozone pollution and/or production for example in field campaigns and investigating reasons for high ozone pollution using observations and model calculations. In addition, contributions analysing trends of ozone concentrations and making suggestions for possible mitigation strategies are welcome.

Over the last decades, Earth’s atmospheric composition has been extensively monitored from space using different techniques and spectral ranges. The GOME (Global Ozone Monitoring Experiment) instrument launched in 1995 by ESA showed that atmospheric space missions with high spectral resolution and coverage can not only be used for ozone monitoring but also to measure a range of trace gases and aerosol for air quality and climate (research) applications. Several decades after these pioneering efforts, continuous progress in instrument design, and retrieval techniques allows operational monitoring of stratospheric and tropospheric concentrations of a wide range of species with implications for air quality and climate. This is well demonstrated with the successful operations of the Sentinel 5 Precursor (S-5P) satellite since 2018.
S-5P is the first of a series of atmospheric missions within the European Commission’s Copernicus Programme and provides continuity in the availability of global atmospheric data products between its predecessor missions SCIAMACHY (Envisat) and OMI (AURA) and the future Copernicus Sentinel-4 and -5 satellite series. The current/future European (Copernicus) atmospheric measurement capabilities are/will be complimented by other space missions like MetOp, MetOp-SG, SUOMI-NPP, GOSAT/2, TanSat, GaoFen 5, OCO2/3, TEMPO, GEMS and others.
This session will include latest results for S-5P operational products (e.g. radiance/irradiance, ozone, nitrogen dioxide, sulfur dioxide, formaldehyde, methane, cloud and aerosol information), results of algorithm studies to develop additional S5-P products (e.g. bromine monoxide, water vapour, glyoxal, AOD, SIF, chlorophyll, and chlorine dioxide) and their geophysical validation. Synergistic data usage or intercomparison results of S-5P measurements with con-current flying missions (e.g. MetOp, GOSAT) and algorithm studies for future mission retrieval algorithms (e.g. Sentinel-4/5) will be addressed. Opportunities that new instrument concepts can bring to the atmospheric air quality and climate monitoring communities will be included as well.

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 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). Marine emissions of active halogens have been linked to 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.

- 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 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.

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 number and size of urban conurbations, which comprise megacities and different urban agglomerations, collectively known as major population centres (MPC), has increased dramatically. By 2050, the population is predicted to rise to ~10 billion with about 75% being urban dwellers. MPCs require power, mostly generated from fossil fuel combustion for their transport systems, industry and domestic heating, cooling etc. MPCs are globally a growing and significant source of emissions of trace gases and aerosols into the troposphere. The air quality in the MPC and the transformation of the emitted pollutants is also often influenced by the transport of biomass burning and pollution plumes. Because of the variability of the naturally occurring emissions of trace constituents, the different characteristics of MPC, the mixing and interaction of the outflow from MPC with those from the surrounding areas, and the need to account for the local topography and meteorology, the assessment and prediction of the impact of pollution from MPC on tropospheric chemistry is challenging. The current knowledge of the effect of this anthropogenic pollution on the air quality and the regional tropospheric chemical composition, and its interaction with climate in a warming world is inadequate.
The trace constituent of interest from MPC emissions are short-lived climate pollutants, their precursors, and long lived greenhouse gases. To assess and better understand the local and regional impact of these pollutants, experimental and modelling investigations of the transformation of MPC emissions during their transport are required. This necessitates the consistent interpretation of observational data sets, having different spatial and temporal resolutions, generated from ground-based networks, airborne campaigns and satellite measurements. This further requires a hierarchy of model studies.
The purpose of this session is to present and discuss results from recent national and international projects studying the emissions from megacities and MPC and their transport and transformation. The session welcomes presentations about relevant observations, data interpretation and modelling studies. One focus is on the studies of MPC emissions from different continents, experiencing different meteorological conditions and the resultant local and regional impacts.

Public information:
In memory of the excellent scientist and colleague Andreas Hilboll

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 polar airborne field campaigns as e.g. the POLSTRACC (Polar Stratosphere in a Changing Climate) and SouthTRAC (Southern Hemisphere - Transport Composition Dynamics) campaign as well as related activities, which aim at providing new scientific knowledge on the Arctic/Antarctic 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.

The radiation budget of the Earth is a key determinant for the genesis and evolution of climate on our planet and provides the primary energy source for life. Anthropogenic interference with climate occurs first of all through a perturbation of the Earth radiation balance. We invite observational and modelling papers on all aspects of radiation in the climate system. A specific aim of this session is to bring together newly available information on the spatial and temporal variation of radiative and energy fluxes at the surface, within the atmosphere and at the top of atmosphere. This information may be obtained from direct measurements, satellite-derived products, climate modelling as well as process studies. Scales considered may range from local radiation and energy balance studies to continental and global scales. In addition, related studies on the spatial and temporal variation of cloud properties, albedo, water vapour and aerosols, which are essential for our understanding of radiative forcings and their relation to climate change, are encouraged. Studies focusing on the impact of radiative forcings on the various components of the climate system, such as on the hydrological cycle, on the cryosphere or on the biosphere and related carbon cycle, are also much appreciated. This session will include a dedicated section with the aim to move towards an harmonization of ground measurements of the surface radiation budget over land and ocean, with particular attention to the definition of best practices, uncertainties and traceability to standards.

Invited Speaker: Robert Weller (Woods Hole Oceanographic Institution, Massachusetts, USA)

Several large ensemble model simulations from General Circulation Models (GCM), Earth System Models (ESM), or Regional Climate Models (RCM), have been generated over the recent years to investigate internal variability and forced changes of the climate system - and to aid the interpretation of the observational record by providing a range of historical climate trajectories that could have been. The increased availability of large ensembles also enables broadening their application to new and inter-disciplinary fields.

This session invites studies using large GCM, ESM, or RCM ensembles looking at the following topics: 1) forced changes in internal variability and reinterpretation of observed record; 2) development of new approaches to attribution of observed events or trends; 3) impacts of natural climate variability; 4) assessment of extreme and compound event occurrence; 5) use of large ensembles for robust decision making; 6) large ensembles as testbeds for method development; and 7) novel methods for efficient analysis and post-processing of large ensembles.

We welcome research across the components of the Earth system and particularly invite studies that apply novel methods or cross-disciplinary approaches to leverage the potential of large ensembles.

Public information:
Announcement: Note that this session will be conducted in two parts:

1) The official #ShareEGU20 live chat. May 8, 14:00-15:45.
Agenda: https://meetingorganizer.copernicus.org/EGU2020/displays/36913

2) An additional live streaming of oral presentations. Friday, May 8, 16:15-18:00.
Agenda: bit.ly/2RX1hd9.
RSVP form: bit.ly/3bvzqZ4

Order of discussion for display items during the live chat:

Nathalie Schaller
2. Bin Yu
3. Benoit Hingray
4. Laura Suarez Gutierrez
5. Flavio Lehner
6. Bo Christiansen
7. Karsten Haustein
8. Renate Wilcke
9. Lea Beusch
10. Andrea Böhnisch
11. Satoshi Watanabe
12. Peter Watson
13. Tamas Bodai
14. Gabor Drotos
15. Gerhard Smiatek
16. Ralf Hand (1st display)
17. Ralf Hand (2nd display)
18. Mátyás Herein

19. Joel Zeder
20. Sebastian Milinski
21. Anna Merrifield
22. Raul R. Wood
23. Shipra Jain
24. Aaron Spring

State of the art climate models are now run for past, present and future climates. This has opened up the opportunity for paleoclimate modelling and data together to inform on future climate changes. To date, most research in this area has been on constraining basic metrics such a climate sensitivity. In addition, and just as importantly for mankind, the Earth's climate is highly variable on all spatial and temporal scales with implications for understanding both the industrial epoch
and future climate projections. These changes in variability (spatial or temporal) can impact the recurrence frequency of extreme events which can have catastrophic effects on society. Yet, it is unclear if a warmer future is one with more or less climate variability, and at which scales. A multitude of feedbacks are involved.

We welcome contributions that improve quantification, understanding and prediction of past, present and future climate and its variability in the Earth System across space and time scales. This includes contributions looking at "steady state" climate features such as climate sensitivity as well as those investigating changes in climate variability and scaling properties. The session is multidisciplinary and brings together studies related to atmospheric science, oceanography, glaciology, paleoclimatology and nonlinear geoscience, to examine the complementarity of ideas and approaches. We particularly encourage submissions that combine models run for the past, present and future with data syntheses to constrain the spread of future predictions, submissions which combine models and data in the past to make strong conclusions or testable hypotheses about the future, as well as work highlighting future experiments and data required to strengthen the link to the future. We welcome contributions using case studies, idealised or realistic modelling, synthesis, and model-data comparison studies that provide insights into past, present and future climate variability on local to global, and synoptic to orbital timescales. Members of the PAGES working group on Climate Variability Across Scales (CVAS) are welcome.

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 variability and predictability of climate in both hemispheres from 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 ecological and socio-economic impacts and encourage submissions on this topic.
The 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 the WWRP Year of Polar Prediction (YOPP), NordForsk-project ARCPATH, and the H2020-projects APPLICATE, INTAROS, BlueAction, and PRIMAVERA.

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

We invite studies

* focusing on the understanding and impacts of features of the atmospheric water cycle related to weather systems, such as Atmospheric Rivers, Cold-Air Outbreaks, Warm Conveyor Belts, Tropical Moisture Exports, and the global Monsoon systems;

* investigating the large-scale drivers behind the variability and trends within the atmospheric water cycle, from long-term observations, reanalysis data, or regional to global model simulations;

* involving and connecting field campaigns (YOPP, MOZAiC, NAWDEX) with forecast and 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 water cycle with characteristics such as the recycling ratio, life time of water vapour, and moisture transport properties.

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

This PICO session addresses three sub-topics :

Precipitation variability: from drop scale to lot scale:
The understanding of small scale (sec – drop scale to min -km) spatio-temporal variability of precipitation is essential for larger scale studies, 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 point measurement devices (rain gauges and disdrometers) and weather radars, which is greater than 10^7! This session aims at bridging this scale gap and improving the understanding of small scale precipitation variability, both liquid and solid, as well as its hydro-meteorological consequences at larger scales.

Hydroclimatic and hydrometeorologic stochastics: Extremes, scales, probabilities:
The departure of statistical properties of hydrometeorological processes from the classical statistical prototype has been established. This session aims at presenting the latest developments on:
- Coupling stochastic approaches with deterministic hydrometeorological predictions;
- Stochastic-dynamic approaches;
- Variability at climatic scales and its interplay with the ergodicity of space-time probabilities;
- Linking underlying physics and scaling stochastics of hydrometeorological extremes;
- Development of parsimonious representations of probability distributions of hydrometeorological extremes over a wide range of scales and states; as well as their applications in risk analysis and hazard predictions
The session is co-sponsored by the ICSH-IAHS, former STAHY.

The atmospheric water cycle under change: feedbacks, land use, hydrological changes and implications :
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. Anthropogenic pressure through land-use changes (and greenhouse gasses) alter, not only, the local hydrology, but through atmospheric water and energy feedbacks also effect the water cycle in remote locations. This session aims to:
- investigate the remote and local atmospheric feedbacks from human interventions, based on observations and coupled modelling approaches.
- explore the implications of atmospheric feedbacks on the hydrologic cycle for land and water management (ex. changing land cover)

One of the most striking features of global climate change is the strongly amplified response of surface air temperature in the Arctic and the associated strong decline in sea ice. Both observational and climate modeling studies have shown that the Arctic is a region very susceptible to climate change; moreover, changes occurring in the Arctic are likely to have more wide-spread implications. Arctic amplification manifests itself in a number of ways, most notably in the current retreat and thinning of Arctic sea ice. A variety of processes and feedbacks have been proposed that contribute to amplified Arctic warming, most of them associated with sea ice. The most well-known is the surface-albedo feedback, which is associated with retreating sea-ice and snow cover. While most climate models exhibit an Arctic amplification signal with respect to ongoing and future changes, the inter-model range in simulated amplification is large, suggesting that the magnitudes of the various feedbacks contributing to Arctic warming and the role of sea ice therein are still uncertain. This session specifically aims to identify, characterize and quantify the processes and feedbacks that govern amplified Arctic warming and sea ice retreat, and it also addresses the climate impacts on the lower latitudes associated with Arctic changes (for instance the relation between sea ice reductions, heat flux changes and atmospheric circulation changes beyond the Arctic region). We therefore invite contributions on the causes, mechanisms and climate feedbacks associated with Arctic climate change and sea ice decline, and the possible links to weather and climate outside the Arctic. We welcome studies based both on climate model results and/or observational datasets, for near-past, present and future climate changes.

The rapid decline of Arctic sea ice in the last decade is a dramatic indicator of climate change. 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, remote sensing and modelling programmes address? The scientific community is investing considerable effort in making the current knowledge of the physical and biogeochemical properties of the Arctic more systematic, in exploring poorly understood coupled atmosphere-sea-ice-ocean processes to improve prediction of future changes in the Arctic.

In this session, we invite contributions from a variety of studies addressing the recent past, present and future Arctic. We encourage submissions examining interactions between the 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, and encourage submissions on the results from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC).

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 closely linked to the session 'Snow and ice accumulation, melt, and runoff generation in catchment hydrology', which addresses monitoring and modelling of snow for hydrologic applications.

The International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) senses the solid Earth, the oceans and the atmosphere with a global network of seismic, infrasound, and hydroacoustic sensors as well as detectors for atmospheric radioactivity. The primary purpose of the IMS data is for nuclear explosion monitoring regarding all aspects of detecting, locating and characterizing nuclear explosions and their radioactivity releases. On-site verification technologies apply similar methods on smaller scales as well as geophysical methods such as ground penetrating radar and geomagnetic surveying with the goal of identifying evidence for a nuclear explosion close to ground zero. Papers in this session address advances in the sensor technologies, new and historic data, data collection, data processing and analysis methods and algorithms, uncertainty analysis, machine learning and data mining, experiments and simulations including atmospheric transport modelling. This session also welcomes papers on applications of the IMS and OSI instrumentation data. This covers the use of IMS data for disaster risk reduction such as tsunami early warning, earthquake hazard assessment, volcano ash plume warning, radiological emergencies and climate change related monitoring. The scientific applications of IMS data establish another large range of topics, including acoustic wave propagation in the Earth crust, stratospheric wind fields and gravity waves, global atmospheric circulation patterns, deep ocean temperature profiles and whale migration. The use of IMS data for such purposes returns a benefit with regard to calibration, data analysis methods and performance of the primary mission of monitoring for nuclear explosions.

The Sendai Framework for disaster risk reduction (SFDRR) and its seventh global target recognizes that increased efforts are required to develop risk-informed and impact-based multi-hazard early warning systems. Despite significant advances in disaster forecasting and warning technology, it remains challenging to produce useful forecasts and warnings that are understood and used to trigger early actions. Overcoming these challenges requires understanding of the reliability of forecast tools and implementation barriers in combination with the development of new risk-informed processes. It also requires a commitment to create and share risk and impact data and to co-produce impact-based forecasting models and services. To deal with the problem of coming into action in response to imperfect forecasts, novel science-based concepts have recently emerged. As an example, Forecast-based Financing and Impact-based Multi-Hazard Early Warning Systems are currently being implemented operationally by both governmental and non-governmental organisations in several countries as a result of increasing international effort by several organizations such as the WMO, World Bank, IFRC and UNDRR to reduce disaster losses and ensuring reaching the objectives of SFDRR. This session aims to showcase lessons learnt and best practices on impact-based multi-hazards early warning system from the perspective of both the knowledge producers and users. It presents novel methods to translate forecast of various climate-related and geohazards into an impact-based forecast. The session addresses the role of humanitarian agencies, scientists and communities at risk in creating standard operating procedures for economically feasible actions and reflects on the influence of forecast uncertainty across different time scales in decision-making. Moreover, it provides an overview of state-of-the-art methods, such as using Artificial Intelligence, big data and space applications, and presents innovative ways of addressing the difficulties in implementing forecast-based actions. We invite submissions on the development and use of operational impact-based forecast systems for early action; developing cost-efficient portfolios of early actions for climate/geo-related impact preparedness such as cash-transfer for droughts, weather-based insurance for floods; assessments on the types and costs of possible forecast-based disaster risk management actions; practical applications of impact forecasts.

The purpose of this session is to: (1) showcase the current state-of-the-art in global and continental scale natural hazard risk science, assessment, and application; (2) foster broader exchange of knowledge, datasets, methods, models, and good practice between scientists and practitioners working on different natural hazards and across disciplines globally; and (3) collaboratively identify future research avenues.
Reducing natural hazard risk is high on the global political agenda. For example, it is at the heart of the Sendai Framework for Disaster Risk Reduction and the Warsaw International Mechanism for Loss and Damage Associated with Climate Change Impacts. In response, the last 5 years has seen an explosion in the number of scientific datasets, methods, and models for assessing risk at the global and continental scale. More and more, these datasets, methods and models are being applied together with stakeholders in the decision decision-making process.
We invite contributions related to all aspects of natural hazard risk assessment at the continental to global scale, including contributions focusing on single hazards, multiple hazards, or a combination or cascade of hazards. We also encourage contributions examining the use of scientific methods in practice, and the appropriate use of continental to global risk assessment data in efforts to reduce risks. Furthermore, we encourage contributions focusing on globally applicable methods, such as novel methods for using globally available datasets and models to force more local models or inform more local risk assessment.
At various scales from global to local, many efforts on the collection and use of loss data related to natural hazards (e.g. cyclone, earthquake, flood, wildfire) as well as open datasets have been made in recent years. The integration of these socioeconomic loss databases and open datasets for loss and risk assessment allow for effective use for both science and policy, and to create a community linking academia, government and insurance.
We also encourage you to submit a manuscript to the NHESS special issue on Global- and continental-scale risk assessment for natural hazards (https://www.nat-hazards-earth-syst-sci.net/special_issue966.html). Deadline for submissions to the special issues is 31 December 2019.

The session gathers geoscientific aspects such as dynamics, reactions, and environmental/health consequences of radioactive materials that are massively released accidentally (e.g., Chernobyl and Fukushima nuclear power plant accidents, wide fires, etc.) and by other human activities (e.g., nuclear tests).

The radioactive materials are known as polluting materials that are hazardous for human society, but are also ideal markers in understanding dynamics and physical/chemical/biological reactions chains in the environment. Thus, the radioactive contamination problem is multi-disciplinary. In fact, this topic involves regional and global transport and local reactions of radioactive materials through atmosphere, soil and water system, ocean, and organic and ecosystem, and its relation with human and non-human biota. The topic also involves hazard prediction and nowcast technology.

By combining 34 years (> halftime of Cesium 137) monitoring data after the Chernobyl Accident in 1986, 9 years dense measurement data by the most advanced instrumentation after the Fukushima Accident in 2011, and other events, we can improve our knowledgebase on the environmental behavior of radioactive materials and its environmental/biological impact. This should lead to improved monitoring systems in the future including emergency response systems, acute sampling/measurement methodology, and remediation schemes for any future nuclear accidents.

The following specific topics have traditionally been discussed:
(a) Atmospheric Science (emissions, transport, deposition, pollution);
(b) Hydrology (transport in surface and ground water system, soil-water interactions);
(c) Oceanology (transport, bio-system interaction);
(d) Soil System (transport, chemical interaction, transfer to organic system);
(e) Forestry;
(f) Natural Hazards (warning systems, health risk assessments, geophysical variability, countermeasure);
(g) Measurement Techniques (instrumentation, multipoint data measurements);
(h) Ecosystems (migration/decay of radionuclides).

The session consists of updated observations, new theoretical developments including simulations, and improved methods or tools which could improve observation and prediction capabilities during eventual future nuclear emergencies. New evaluations of existing tools, past nuclear contamination events and other data sets also welcome.

Meridional flows of heat and moisture are largely driven by global patterns of energy surplus and deficit and sensitive to multiple forcings and feedbacks. The large-scale atmospheric-oceanic circulation and the hydrological cycle are tightly intertwined with such heat and moisture transports.
For example, inter-hemispheric energy asymmetries play an important role in modulating the strength of the Hadley Circulation, which in turn modulates the low-level mass convergence and the amount of precipitation in the ITCZ and in monsoon regions. In the extra-tropics, Rossby waves affect the distribution of precipitation and eddy activity, shaping the meridional heat transport from the low latitudes towards the Poles.
We invite submissions addressing the interplay between Earth’s energy exchanges and the response of the general circulation using modeling approaches, theoretical considerations, and observations.
We also encourage contributions on dynamics, trends, characteristics and past-to-future variability of mean meridional circulation and its impact on regional climate.

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;
· Extremes in dynamical systems;
· Downscaling of weather and climate extremes.
· Linking the dynamics of climate extremes to their impacts

This session primarily focuses on the neutral atmospheres of terrestrial bodies other than the Earth. This includes not only Venus and Mars, but also exoplanets with comparable envelopes and satellites carrying dense atmospheres such as Titan or exospheres such as Ganymede. We welcome contributions dealing with processes affecting the atmospheres of these bodies, from the surface to the exosphere. We invite abstracts concerning observations, both from Earth or from space, modeling and theoretical studies, or laboratory work. Comparative planetology abstracts will be particularly appreciated.

This session addresses interactions of plasma and (charged) dust in the vicinity and on the surfaces of small solar system objects and in planetary ionospheres, including meteor phenomena. Surface interactions were observed at several different objects including Mercury, Pluto, asteroids, comets, Kuiper belt objects, and a number of moons. Sub-surface layers influence the electromagnetic field locally and, in this way, can be measured remotely. Furthermore, observed surface properties and exospheres are strongly influenced by complex interactions between the dusty/icy regolith, micro-meteoroids, the plasma environment and UV radiation. These processes in turn affect the plasma conditions of the surroundings. A particular case are the moons of the giant planets where interactions occur with the magnetospheres of their host planets. In this session we invite contributions that will move forward our understanding of electromagnetic, surface-plasma and dust-plasma interaction with (small) solar system bodies. The different topics include (but are not limited to) the physics of meteors and of dust in ionospheres, fundamental electromagnetic interactions of satellites enclosed in diverse atmospheric envelopes, the physics of plumes and their influence on the local electromagnetic fields, the electromagnetic effects of sub-surface (magma) oceans, ionospheric phenomena and space weathering of surfaces.

Processes responsible for formation and development of the early Earth (> 2500Ma) are not
well understood and strongly debated, reflecting in part the poorly preserved, altered, and
incomplete nature of the geological record from this time.
In this session we encourage the presentation of new approaches and models for the development of Earth's early crust and mantle and their methods of interaction. We encourage contributions from the study of the preserved rock archive as well as geodynamic models of crustal and mantle dynamics so as to better understand the genesis and evolution of continental crust and the stabilization of cratons.
We invite abstracts from a large range of disciplines including geodynamics, geology, geochemistry, and petrology but also studies of early atmosphere, biosphere and early life relevant to this period of Earth history.

Stable isotopes and other novel tracers, such as carbonyl sulfide (COS) and clumped isotopes, help to identify and quantify biological, chemical and physical processes that drive Earth's biogeochemical cycling, atmospheric processes and biosphere-atmosphere exchange. Recent developments in analytical measurement techniques now offer the opportunity to investigate these tracers at unprecedented temporal and spatial resolution and precision.

This session includes contributions from field and laboratory experiments, latest instrument developments as well as theoretical and modelling activities that investigate and use the isotope composition of light elements (C, H, O, N) and their compounds as well as other novel tracers for biogeochemical and atmospheric research.

Topics addressed in this session include:
- Stable isotopes in carbon dioxide (CO2), water (H2O), methane (CH4) and nitrous oxide (N2O)
- Novel tracers and biological analogues, such as COS
- Polyisotopocules ("clumped isotopes")
- Intramolecular stable isotope distributions ("isotopomer abundances")
- Analytical, method and modelling developments
- Flux measurements
- Quantification of isotope effects
- Non-mass dependent isotopic fractionation and related isotope anomalies

Fire is an essential feature of terrestrial ecosystems and an important component of the Earth system. Climate, vegetation characteristics, and human activity regulate fire occurrence and spread, but fires also feedback to them in multiple ways. The mechanisms of interactions between fire, land, atmosphere, and society are complicated and remain poorly understood quantitatively. This session welcomes contributions on all aspects of links between fire, biosphere, climate, and humans to share recent advances and foster interdisciplinary discussions. We encourage all abstracts that explore the role of fire in the Earth system at any temporal and spatial scale using modeling, field and laboratory observations, and/or remote sensing, with an emphasis on studies that advance our understanding on (1) impacts of fire on weather, climate, and atmospheric chemistry, (2) interactions between fire, biogeochemical cycles, land water and energy budgets, and vegetation composition and structure, (3) influence of humans on fire and vice versa (e.g., impact of fire on air and water quality, human health, and economy), (4) fire characteristics (e.g. fire duration, emission factor, emission height, smoke transport), (5) spatial and temporal changes of fires in the past, present, and future, (6) fire products and models, and their validation and error/bias assessment, and (7) analytical tools designed to enhance situational awareness among fire practitioners and early warning systems, addressing specific needs of operational fire behavior modeling.

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 in its pristine and degraded state is elemental for predicting its response upon changing climate and land use, and the impact this will have on local up to global scale.
This session aims at bringing together scientists who investigate the functioning of the Amazon and comparable forest landscapes across spatial and temporal scales by means of remote and in-situ observational, modelling, 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.

This session is linked to the Pan-Eurasian EXperiment (PEEX; www.atm.helsinki.fi/peex), a multi-disciplinary, -scale and -component climate change, air quality, environment and research infrastructure and capacity building programme. It is aimed at resolving major uncertainties in Earth system science and global sustainability issues concerning the Arctic, Northern Eurasia and China regions. This session aims to bring together researchers interested in (i) understanding environmental changes effecting in pristine and industrialized Pan-Eurasian environments (system understanding); (ii) determining relevant environmental, climatic, and other processes in Arctic-boreal regions (process understanding); (iii) the further development of the long-term, continuous and comprehensive ground-based, air/seaborne research infrastructures together with satellite data (observation component); (iv) to develop new datasets and archives of the continuous, comprehensive data flows in a joint manner (data component); (v) to implement validated and harmonized data products in models of appropriate spatio-temporal scales and topical focus (modeling component); (vi) to evaluate impact on society though assessment, scenarios, services, innovations and new technologies (society component).
List of topics:
• Ground-based and satellite observations and datasets for atmospheric composition in Northern Eurasia and China
• Impacts on environment, ecosystems, human health due to atmospheric transport, dispersion, deposition and chemical transformations of air pollutants in Arctic-boreal regions
• New approaches and methods on measurements and modelling in Arctic conditions;
• Improvements in natural and anthropogenic emission inventories for Arctic-boreal regions
• Physical, chemical and biological processes in a northern context
• Aerosol formation-growth, aerosol-cloud-climate interactions, radiative forcing, feedbacks in Arctic, Siberia, China;
• Short lived pollutants and climate forcers, permafrost, forest fires effects
• Carbon dioxide and methane, ecosystem carbon cycle
• Socio-economical changes in Northern Eurasia and China regions.
PEEX session is co-organized with the Digital Belt and Road Program (DBAR), abstracts welcome on topics:
• Big Earth Data approaches on facilitating synergy between DBAR activities & PEEX multi-disciplinary regime
• Understanding and remote connection of last decades changes of environment over High Asia and Arctic regions, both land and ocean.

Volcanic emission can have a strong impact on the Earth’s radiation budget and climate over a range of temporal and spatial scales, depending on the activity type (passive degassing and small magnitude to strong explosive eruptions).
It is now well known that strong explosive volcanic eruptions are a major natural driver of climate variability at interannual to multidecadal time scales. Assessment of volcanically-forced climate variability is complicated by many limiting factors, including the paucity of observed eruptions, uncertainties in volcanic forcing datasets for the current and pre-instrumental periods, limitations of proxy-based climate evidence, uncertainties of global aerosol model simulations and the apparent large inconsistencies in the responses to volcanic forcing simulated by current climate models. Quiescent passive degassing and smaller-magnitude eruptions on the other hand can impact on regional climate system. In addition, volcanic emissions may influence local-to-regional air quality, seriously affect the biosphere and environment, and the release of gas from soil may pose long-term health hazards. This session focuses on new results from integrative research on the climatic, environmental and societal impacts of the volcanic activity, including eruptions of Pinatubo-magnitude and larger, volcanic degassing and small eruptions.

We aim to highlight contributions conducted under the umbrella of the CMIP6 and in particular VolMIP activity that explore the responses of the coupled ocean-atmosphere system to volcanic forcing, from the characterization of the mechanism of volcanically-forced climate variability and on the potential role of volcanic eruptions on future climate variability and predictability by means of observations, climate reconstruction studies and modeling approaches. We also welcome contributions conducted under PAGES-VICS activities from research aimed at better understanding volcanic impacts on historical and modern societies. We also invite contribution to the current international SPARC-SSiRC program, observational and modelling studies of the 2019 Raikoke aerosol cloud and from recent field campaigns. We further invite new results from H2020 transnational accesses to volcanic platforms and cross-studies coupling volcanology/atmospheric/health hazards, aspects of volcanic plumes science, their observation, modelling and impacts.

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: Anna von der Heydt (Utrecht University)