Erdsystem-Modellierung

Head

Jun. - Prof. Dr. Holger Tost


Staff

Dipl. Harald Rybka

 




Institute for Atmospheric Physics
Johannes Gutenberg University Mainz
J.-J.-Becherweg 21
55128 Mainz
Germany

Phone: +49-(0)6131-39-25968


Research Interests

Influence of Convection Parameterisations in large scale models

Several convection parameterisations have been developed to consider the impact of small-scale unresolved processes in Earth System Models associated with convective clouds. The influence of convection schemes in general circulation models concerns a variety of atmospheric processes like the transport of trace gases, formation of precipitation etc. The parameterised mechanims induce a variety of uncertainties concerning climate change scenarios.
The plot shows the relative change in 30° zonally averaged Radon concentrations for a 2xCO2 scenario considering four different convection schemes.


Superparameterisations

Cloud Resolving Models (CRMs) covering a horizontal grid spacing from a few hundred meters up to a few kilometers have been used to explicitly resolve small-scale and mesoscale processes. Special attention has been paid to realistically represent cloud dynamics and cloud microphysics involving cloud droplets, ice crystals, graupel and aerosols. The entire variety of physical processes on the small-scale interacts with the larger-scale circulation and has to be parameterised on the coarse grid of a general circulation model (GCM). Since more than a decade an approach to connect these two types of models which act on different scales has been developed to resolve cloud processes and their interactions with the large-scale flow. The concept is to use an ensemble of CRM grid cells in a 2D or 3D configuration in each grid cell of the GCM to explicitly represent small-scale processes avoiding the use of convection and large-scale cloud parameterisations which are a major source for uncertainties regarding clouds. The idea is commonly known as superparameterisation or cloud-resolving convection parameterisation.
I investigate the influence of this newly implemented parameterisation on the atmospheric temperature, precipitation patterns and cloud occurence. Furthermore, different transport routines are observed which reflect the fast convective transport of short-lived tracers like radon or methyl iodide.


Earth System Modelling
The global interactions and feedbacks of atmospheric chemistry and the climate of the Earth system can only be described and analysed with the help of comprehensive Earth System Models.
For that purpose I develop and apply the global chemistry climate model EMAC .
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