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

We invite studies

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


-- Notes --

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Precipitation variability: from drop scale to lot scale

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


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Heat extremes are already one of the deadliest meteorological events and they are projected to increase in intensity and frequency due to rising CO2 emissions. Thus the risk these events pose to society may increase dramatically and society will need to adapt if the worst impacts are to be avoided. However, uncertainties for understanding the development of extreme heat episodes and their impacts remain large. This session therefore aims to address this challenge, welcoming research which improves our understanding of extreme heat events and how to respond to them. Suitable contributions in this regard may: (i) assess the drivers and underlying processes of extreme heat in observations and models; (ii) explore the diverse socio-economic impacts of extreme heat events (for example, on aspects relating to human health or economic productivity); (iii) address forecasting of extreme heat at seasonal to sub-seasonal time scales; (iv) focus on societal adaptation to extreme heat, including (but not limited to) the implementation of Heat-Health Early Warning Systems.

In spring and summer 2018, Central and Northern Europe faced a severe drought with rainfall deficits beginning as early as April and lasting until late August in some regions (partly combined with a heat wave in July and August). Due to higher spring temperatures and high radiation the Baltic Sea showed a very unusal low pCO2 signal since late April and a spectacular summer bloom this year. The impact on terrestrial ecosystems became obvious through crop failure and forest fires. This transdiciplinary session calls for scientific results from Earth Observation showing the impact of the drought and for presentations from the interface between science a climate action e.g. adaptation strategies, questions on measuring, reporting and verification of inventories or general communication of climate change to societies.

International failure in curbing the global greenhouse gas emissions has sparked studies on diverse and largely hypothetical methods, known collectively as geoengineering, to intentionally mitigate climate change. At the same time, operational activities to modify weather, especially in terms of snow and rain enhancement, are taking place in more than 50 countries. Although these two topics are typically discussed separately, they are in many ways interlinked. Importantly, successful long-term weather modification and geoengineering would alter climatic conditions and the water cycle on local to regional scales.
In this session, the nexus between regional geoengineering and weather modification is discussed and analyzed. The importance of regional-scale modeling and experimental studies is specifically highlighted. All contributions are welcome, which investigate the various geoengineering and weather modification options from the local to the regional scale. Particularly encouraged are studies, which consider potential interlinkages between geoengineering and rain enhancement.

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 dedicated sections on the contribution of far-infrared radiation and surface temperature to the Earth radiation budget and climate.

Several large ensemble model simulations, either from Global Climate Models (GCM), Earth System Models (ESM), or Regional Climate Models (RCM), have been generated over the recent years. These ensembles, typically simulating historical climate and making future projections, are powerful because they can be used to accurately estimate forced changes in the climate system and to determine the magnitude and realism of simulated internal climate variability. They can further be applied to investigate how climate change signals may emerge from internal variability over time. Combining large ensemble simulations also provides long time series to investigate the dynamics of hydro-meteorological extremes and to assess compound events (e.g., successive or simultaneous extreme events) under conditions of climate change.

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 event occurrence in historical and future climate; 5) development of projections for compound events; 6) comparison of large ensembles including uncertainty assessment; and 7) novel methods for efficient analyses 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.

In both climate modelling and numerical weather prediction, numerical models of the Earth System are used extensively. For the both the atmosphere and ocean such models consist of a fluid dynamics solver (dynamical core) coupled to physics parameterizations to represent processes that occur below the grid scale (physics). Over time these models have become capable of sophisticated simulations, incorporating such features as multi-scale prediction, structure-preserving discretization and a detailed treatment of physics. New work is constantly being undertaken to improve the accuracy and efficiency of these models, both the dynamical core and the physics.

This session encompasses the development, testing and application of novel numerical techniques for Earth system models, including new discretizations, test cases, advection schemes, vertical discretizations, adaptive multi-scale models, physics-dynamics coupling, global and regional climate and NWP models, structure-preserving discretizations and parameterizations (that are not covered in other sessions).

Models of the class used in the CMIP6 experiment to make global
climate projections are imperfect representations of reality that
differ widely in regard to the overall magnitude of warming, in their
regional projections, and in their short-range predictions. While
better models of the underlying physical processes are ultimately
needed, immediate improvement may come simply from better methods to
combine existing models. Contributions are solicited on new methods to
fuse models of climate and weather ranging from output averaging techniques to methods that
dynamically combine model components in a synchronizing, interactive
ensemble. The importance (or lack thereof) of nonlinearities in
determining the sufficiency of output averaging is a topic of special
interest.

Remote sensing techniques and earth system modelling have been widely used in earth science and environmental science. In particular, the world is suffering significant environmental changes such as hydro-climatic extremes, sea level rise, melting glaciers and ice caps and forest fires. The earth observations and earth system models provide valuable insight into climate variability and environmental change. Meanwhile, the question on how to derive and present uncertainties in earth observations and model simulations has gained enormous attention among communities in the earth sciences.

However, quantification of uncertainties in satellite-based data products and model simulations is still a challenging task. Various approaches have been proposed within the community to tackle the validation problem for satellite-based data products and model simulations. These progress include theory advancement, mathematics, methodologies, techniques, communication of uncertainty and traceability.

The aim of this session is to summarize current state-of-the-art in uncertainty quantification and utilization for satellite-based earth observations and earth system models.

Numerical atmospheric dispersion models are an essential tool for assessment of emergency situations related to airborne particles or gases released into the atmosphere by natural or man-made hazards. They are used complementary to observational data in order to fill-in e.g. temporal- or spatial gaps and to conduct forecasts facilitating the planning of mitigation strategies.
The focus of this session will be on environmental emergency scenarios (airborne hazards) which can have extremely high impact on society and environment: volcano eruptions, nuclear accidents, as well as more localised emergencies, such as dust storms and strong vegetation fires or other occasions when hazardous pollutants are injected into the atmosphere.

The session gathers geoscientific aspects such as dynamics, reactions, and environmental/health consequences of radioactive materials that are massively released accidentally (e.g., Fukushima and Chernobyl 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 chemical/biological/electrical 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 >30 year (halftime of Cesium 137) monitoring data after the Chernobyl Accident in 1986, >5 year 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);
(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.

Public information:
The release of radioactive materials by human activity (such as nuclear accidents) are both severe hazard problem as well as ideal markers in understanding geoscience at all level of the Earth because it cycles through atmosphere, soil, plant, water system, ocean, and lives. Therefore, we must gather knowledge from all geoscience field for comprehensive understanding.

Fire is a global phenomenon influencing ecosystem functioning, carbon stocks and fluxes, and atmospheric composition, with large impacts on human health, safety and economy. The relative importance of climate, vegetation and humans as drivers of fire activity varies across spatial and temporal scales. Multiscale and interdisciplinary assessments of fire behavior are required to understand global climate-fire feedbacks, as well as regional interactions between vegetation and humans, and fire.
Fire influences the global carbon cycle among others through its carbon emissions and post-fire ecosystem carbon sequestration. In addition, black carbon (also known as pyrogenic carbon, charcoal, soot) is a crucial component in the carbon cycle, yet uncertainties remain regarding sizes, losses and fluxes between land, rivers, oceans and atmosphere.
Remote sensing provides baseline information for all stakeholders involved in monitoring of biomass burning at different scales and for understanding how ecosystems respond to fires. However, there are still large uncertainties in satellite-based active fire, burned area, and fire emissions estimates, in part due to the complexity and diversity of the ecosystems affected. Building on the environmental significance and scientific challenges described above, this session will bring together fire scientists working on biomass burning monitoring and early warning systems. The aim of this session is to improve the understanding of interactions between fire, vegetation, carbon, climate and humans. We invite contributions developing or using remote sensing datasets, in situ observations, charcoal records, laboratory experiments and modeling approaches. We welcome studies that help to improve our understanding of (1) the relative importance of climate, vegetation and humans on fire occurrence across spatial and temporal scales (2) the impacts of fire on vegetation, atmosphere and society, (3) feedbacks between fire, vegetation and climate, and (4) the role of fire in the carbon cycle, with special focus on the transfer of black carbon and other fire markers from terrestrial ecosystems to aquatic environments, and their biogeochemical fate in these environments, (5) innovative use of remote sensing technologies (LIDAR, infrared cameras, drones) for fuel characterization, fire detection and monitoring; (6) algorithms/models applicable to regional-to-global scale fire analyses exploring active fire detection and characterization (e.g., fire radiative power, area affected, combustion phase), burned area mapping, atmospheric emissions and smoke transport, (7) fire product validation and error assessment, (8) analytical tools designed to enhance situational awareness among fire practitioners and early warning systems, addressing specific needs of operational fire behavior modeling.

Invited speakers:
Emilio Chuvieco, University of Alcala
Elena Kukavskaya, Sukachev Institute of Forest, Russian Academy of Sciences

The Tibetan Plateau and surrounding mountain regions, known as the Third Pole, cover an area of > 5 million km2 and are considered to be the water tower of Asia. The Pan Third Pole expands on both the north-south and the east-west directions, going across the Tibetan Plateau, Pamir, Hindu Kush, Iran Plateau, Caucasian and Carpathian, and covering an area of about 20 million km2. Like the Arctic and Antarctica, the Pan Third Pole’s environment is extremely sensitive to global climate change. In recent years, scientists from around the globe have increased observational, remote sensing and numerical modeling research related to the Pan Third Pole in an effort to quantify and predict past, current and future scenarios. Co-sponsored by TPE (www.tpe.ac.cn), this session is dedicated to studies of Pan Third Pole atmosphere, cryosphere, hydrosphere, and biosphere and their interactions with global change. Related contributions are welcomed.

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).

A planned outcome of this session is a summary document providing a mountains perspective and input for the IPCC Sixth Assessment Report, more specifically for Working Group I report on the Physical Sciences Basis and the cross-chapter paper on 'Mountains', which is flagged for the Working Group II report. This summary document is organized and supported by the Mountain Research Initiative (MRI).

The occurrence of extremes such as droughts, flash floods, hailstorms, storm surges and tropical storms can have significant and sometimes catastrophic consequences to society. However, not all low probability weather/climate events will lead to “high impacts” on human or natural systems or infrastructure. Rather, the severity of such events depend also intrinsically on the exposure, vulnerability and/or resilience to such hazards of affected systems, including emergency management procedures. Similarly, high impact events may be compounded by the interaction of several, e.g., in their own right less severe hydro-meteorological incidents, sometimes separated in time and space. Or they may similarly result from the joint failures of multiple human or natural systems. Consequently, it is a deep transdisciplinary challenge to learn from past high impact events, understand the mechanisms behind them and ultimately to project how they may potentially change in a future climate.

The ECRA (European Climate Research Alliance) Collaborative Programme on “High Impact Events and Climate Change” aims to promote research on the mechanisms behind high impact events and climate extremes, simulation of high impact events under present and future climatic conditions, and on how relevant information for climate risk analysis, vulnerability and adaptation may be co-created with users, e.g., in terms of tailored climate services. For this aim, this Interdisciplinary and Transdisciplinary Session invites contributions that will serve to (i) better understand the mechanisms behind high impact events from a transdisciplinary and interdisciplinary perspective, e.g. case studies and the assessment of past high impact events, including detection and attribution; (ii) project changes to high impact events through, e.g. high resolution climate and impacts modelling (including economic modelling); (iii) produce climate information at the relevant scales (downscaling); and co-create climate services with users to help deal with the risk and/or impacts of high-impact events, e.g. risk analysis and climate adaptation. Abstracts that highlight recent advances from a transdisciplinary perspective for example through the innovation of climate services will be particularly encouraged. Authors and contributors to this session will be offered to present their work in a Special Issue of the journal “Sustainability”.

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 together with the EU H2020 ANYWHERE project will coordinate 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 and ANYWHERE to the research community. We therefore invite papers studying Compound Events and addressing the following topics representing the five working groups of DAMOCLES and Work Package 2 of ANYWHERE working on multi-hazard impacts..

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?

As discussed by EGU2017 DB2 and EGU 2018 TM16, there had been an impressive series of international agreements and development of large networks of cites that call for qualitative improvements of urban systems and their interactions with their environment. The main goal of this ITS is to mobilise geoscientists, highlight their present contributions and encourage holistic approaches beyond the traditional silos of urban meteorology/hydrology/climatology/ecology/resilience, as well as some other terms.

Public information:
See also Town Hall TM 19 "Cities and Interdisciplinary Geosciences"
to be held on Thursday 11 April in room 1.85 from 19:00 to 20:00.
https://meetingorganizer.copernicus.org/EGU2019/session/33913

As the most evident example of land use and land cover change, urban areas play a fundamental role in local to large-scale planetary processes, via modification of heat, moisture, and chemical budgets. With rapid urbanization ramping up globally it is essential to recognize the consequences of landscape conversion to the built environment. Given the capability of cities to serve as first responders to global change, considerable efforts are currently being dedicated across many cities to understand urban atmospheric dynamics and examine various adaptation and mitigation strategies aimed to offset impacts of rapidly expanding urban environments and influences of large-scale greenhouse gas emissions.

This session solicits submissions from both the observational and modelling communities examining urban atmospheric dynamics, processes and impacts owing to urban induced climate change, the efficacy of various strategies to reduce such impacts, and techniques highlighting how cities are already using novel science data and products that facilitate urban adaptation to and mitigation of the effects of climate change.

Cities all over the world are facing rising population densities. This leads to increasing fractions of built-up and sealed areas, consequencing in a more and more altered and partly disrupted water balance - both in terms of water quantities and qualities. On top, climate change is altering precipitation regimes.

This session focuses on according urban ecohydrological problems and approaches to solve them spanning from technical to nature-based solutions in different time and spatial scales from the building to the whole city.

The study of the ionized and neutral atmosphere reveals to be an efficient diagnostic tool to understand the interaction among the geospheres and the impact of the solar wind on the Earth. Any variation from the expected behaviour can be helpful to identify various forcing mechanisms originated from below and above. The vertical coupling in the atmosphere involves the influence of the upper atmospheric layers on climate and the response of the ionosphere to the modification of neutral atmosphere chemistry and dynamics. An exacerbation in the space weather conditions, in turn, can cause changes in the neutral composition and in the electron density structuring. In addition, natural hazards, such as tsunami, earthquakes, thunderstorms can produce atmospheric acoustic gravity waves that result in electron density perturbations in the ionosphere.
The broad availability of instruments on board satellites and hosted at ground opens new opportunities of multi-disciplinary and multi-instruments collaboration to advance the current understanding in the field.
This session welcomes observational, theoretical, and modeling contributions on atmospheric irregularities to identify the coupling mechanisms within the atmosphere, between the atmosphere and the lithosphere, and between the atmosphere and the geospace.

'Cosmic rays’ collectively describe particles that bombard the Earth from space. They carry information about space and, once near the Earth, interact with the magnetosphere, atmosphere, hydrosphere and lithosphere. Secondary cosmic rays created within the atmosphere can provide information about our planet that is vital to science and society. Secondary neutron radiation plays an extraordinary role, as it not only carries information about solar activity, but also produces short and long living tracer isotopes, influences genetic information of living organisms, and is extraordinarily sensitive to hydrogen and therefore also to water. Given the vast spectrum of interactions of cosmic rays with matter in different parts of the Earth, cosmic-ray research ranges from studies of the solar system to the history of the Earth, and from health and security issues to hydrology and climate change.

Although research on cosmic-ray particles is connected to a variety of disciplines and applications, they all share similar questions and problems regarding the physics of detection, modeling, and environmental factors that influence the intensity. Questions that all disciplines have in common are, for example, “How does the cosmic-ray intensity and energy spectra change with time and location on Earth?”, “How to correct the signal for magnetospheric or atmospheric fluctuations?”, “What is the influence of local structures, water bodies, and surface conditions?”, “Which computer model for cosmic-ray propagation is correct?”, or “What can we learn from other types of cosmic-ray particles?”.

The session brings together scientists from all fields of research that are related to monitoring and modeling of cosmogenic radiation. It will allow sharing of expertise amongst international researchers as well as showcase recent advancements in their field. The session aims to stimulate discussions about how individual disciplines can share their knowledge and benefit from each other.

We solicit contributions related but not limited to:
- Health, security, and radiation protection: cosmic-ray dosimetry on Earth and its dependence on environmental and atmospheric factors
- Planetary space science: satellite and ground-based neutron and gamma-ray sensors to detect water and soil chemistry
- Neutron monitor research: detection of high-energy cosmic rays variations and its dependence on local and atmospheric factors
- Hydrology and climate change: low-energy neutron sensing to measure water in reservoirs at and near the land surface, such as soils, snow pack and vegetation
- Cosmogenic nuclides: as tracers of atmospheric circulation and mixing; as a tool in archaeology or glaciology for dating of ice and measuring ablation rates; and as a tool for surface exposure dating and measuring rates of surficial geological processes
- Detector design: technological advancements for the detection of cosmic rays
- Cosmic-ray modeling: advances in modeling of the cosmic-ray propagation through the magnetosphere and atmosphere, and their response to the Earth’s surface
- Impact modeling: How can cosmic-ray monitoring support environmental models, weather and climate forecasting, irrigation management, and the assessment of natural hazards

The session aims to collect original or review contributions on the use of data from Low-Earth-Orbiting (LEO) satellites making measurements in the thermosphere-ionosphere to investigate ionospheric anomalies related to space weather, geophysical and artificial sources. In fact, data from LEO satellites can provide a global view of near-Earth space variability and are complementary to ground-based observations, which have limited global coverage. The AMPERE project and integration of the Swarm data into ESA’s Space Weather program are current examples of this. The availability of thermosphere and ionosphere data from the DEMETER satellite and the new operative CSES mission demonstrates that also satellites that have not been specifically designed for space weather studies can provide important contributions to this field. On the other hand, there are evidences that earthquakes can generate electromagnetic anomalies into the near Earth space. A multi-instrumental approach, by using ground observations (magnetometers, magnetotelluric stations, GNSS receivers, etc.) and LEO satellites (DEMETER, Swarm, CSES, etc.) measurements can help in clarifying the missing scientific knowledge of the lithosphere-atmosphere-ionosphere coupling (LAIC) mechanisms before, during and after large earthquakes. We also solicit contributions on studies about other phenomena, such as tropospheric and anthropogenic electromagnetic emissions, that influence the near-Earth electromagnetic and plasma environment on all relevant topics including data processing, data-assimilation in models, space weather case studies, superimposed epoch analyses, etc.

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.

The solar system terrestrial planets, and especially the Earth, provide the best opportunity to learn about the basic physical principles of rocky planets, which can then be applied to the evolution of exoplanets and their atmospheres. Similarly, knowledge of the diversity and properties of exoplanetary systems can provide important information about the formation and evolution of our own solar system. In this session, we will focus on general discussions of exoplanetary science, and especially the application of solar system based knowledge to exoplanets and understanding how the Earth can be understood in the exoplanetary context. Of particular interest are studies of atmospheric evolution due to surface-atmosphere interactions and atmospheric losses to space, as well as interactions between stars and planets. Topics include recent advances in observations of (exo)planets lying in the habitable zone, model studies calculating the habitable zone boundaries, factors affecting habitability including atmospheric processes (e.g. outgassing, escape), high energy particles, remote biosignatures and their spectra, planned missions such as JWST, PLATO, E-ELT, LUVOIR, HABEX and ELF and their impact on our knowledge of exoplanetary habitability.

The InSight mission to Mars landed in Elysium Planitia on November 26. InSight's scientific objective is the study of the Martian interior using two seismometers, a heat flow probe and geodetical measurements. Auxiliary instruments will collect meteorological and magnetic data for at least one Martian year.
This session provides initial results from Mars, status reports of instrument deployment and relevant pre-landing science.

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.

From the real-time integration of multi-parametric observations is expected the major contribution to the development of operational t-DASH systems suitable for supporting decision makers with continuously updated seismic hazard scenarios. A very preliminary step in this direction is the identification of those parameters (seismological, chemical, physical, biological, etc.) whose space-time dynamics and/or anomalous variability can be, to some extent, associated with the complex process of preparation of major earthquakes.
This session wants then to encourage studies devoted to demonstrate the added value of the introduction of specific, observations and/or data analysis methods within the t-DASH and StEF perspectives. Therefore studies based on long-term data analyses, including different conditions of seismic activity, are particularly encouraged. Similarly welcome will be the presentation of infrastructures devoted to maintain and further develop our present observational capabilities of earthquake related phenomena also contributing in this way to build a global multi-parametric Earthquakes Observing System (EQuOS) to complement the existing GEOSS initiative.
To this aim this session is not addressed just to seismology and natural hazards scientists but also to geologist, atmospheric sciences and electromagnetism researchers, whose collaboration is particular important for fully understand mechanisms of earthquake preparation and their possible relation with other measurable quantities. For this reason all contributions devoted to the description of genetic models of earthquake’s precursory phenomena are equally welcome. Every 2 years selected papers presented in thsi session will be proposed for publication in a dedicated Special Issue of an international (ISI) scientific journal.

Natural hazards and climate change impacts in coastal areas
Coastal areas are vulnerable to ocean, atmospheric and land-based hazards. This vulnerability is likely to be exacerbated in future with, for example, sea level rise, increasing intensity of tropical cyclones, increased subsidence due to groundwater extraction. Drawing firm conclusions about current and future changes in this environment is challenging because uncertainties are often large. This calls for a better understanding of the underlying physical processes and systems. Furthermore, while global scale climate and detailed hydrodynamic modelling are reaching a mature development stage the robust assessment of impacts at regional and local scales remains in its infancy. Numerical models therefore play a crucial role in characterizing coastal hazards and assigning risks to them.

This session invites submissions focusing on assessments and case studies at global and regional scales of potential physical impacts of tsunamis, storm surge, sea level rise, waves, and currents on coasts. We also welcome submissions on near-shore ocean dynamics and also on the socio-economic impact of these hazards along the coast.

Tipping elements in the Earth's climate system are continental-scale subsystems that are characterized by a threshold behavior. It has been suggested that these include biosphere components (e.g. the Amazon rainforest and coral reefs), cryosphere components (e.g. the Greenland and Antarctic ice sheets) and large-scale atmospheric and oceanic circulations (e.g. the thermohaline circulation, ENSO and Indian summer monsoon). Once operating near a threshold or tipping point, these components can transgress into a qualitatively different state by small external perturbations. The large-scale environmental consequences could impact the livelihoods of millions of people.

In this session, we aim to bring together experts presenting and discussing the state-of-the-art research on tipping elements in the Earth's climate system, both in empirical data and numerical modelling of past, present and future climate. Among other topics, issues to be addressed in this session include critical thresholds for specific tipping elements, typical time scales of tipping, interactions and feedbacks between tipping elements, the potential for tipping cascades as well as environmental and socio-economic impacts of tipping.