EGU2019 Sessions mit HD(CP)² chairs:

Atmospheric Convection 

Convener: Cathy Hohenegger
Co-conveners: Leo Donner, Holger Tost

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

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

-chemistry and chemical transport in convection


Coupled atmosphere-hydrological modeling for improved hydro-meteorological prediction (co-organized)

Convener: Harald Kunstmann
Co-conveners: Martin Drews, Stefan Kollet, Alfonso Senatore

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.


Clouds, moisture, and precipitation in the polar regions: Sources, processes and impacts (co-organized)

Convener: Manfred Wendisch
Co-conveners: Susanne Crewell, Irina V. Gorodetskaya, Tom Lachlan-Cope, Nicole van Lipzig

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.


Impact of Land-Atmosphere Feedbacks on Weather and Climate (co-organized)

Convener: Volker Wulfmeyer
Co-conveners: Matthias Mauder, Linda Schlemmer, Chiel van Heerwaarden

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.


Coupled Data Assimilation for Earth System Models (co-organized)

Convener: Harrie-Jan Hendricks Franssen
Co-conveners: Gabriëlle De Lannoy, Lars Nerger, Insa Neuweiler, Clemens Simmer

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 different compartments. This session focuses on weakly and strongly coupled data assimilation 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.

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