Precipitating Convection

 

Group Leader: Cathy Hohenegger

 

Our group aims to understand the processes that set basic features of the climatological distribution of precipitation, with a particular emphasis on the role that interactions between convection and the surface  play in setting this distribution.  In this context, we focus on two aspects of the precipitation distribution: the role of the land surface in setting  the mean precipitation amount over land;  and the role of ocean-atmosphere interactions in setting properties of the InterTropical Convergence Zone. The strength of the coupling between convection and the underlying surface is virtually unknown, being set by the convective parameterization in traditional Earth System Models, whereas in storm-resolving regional climate models, it is spuriously constrained by the limited domain size. Our inability to understand basic features of the precipitation distribution, in part due to the use of inappropriate modelling tools, undermines confidence in our ability to answer more subtle questions, like how precipitation may change with warming.

Given these interests, being able to represent convection explicitly on global domains and the surface dynamically is of crucial importance for our research and explains the leadership role that we take in the MPI internal Sapphire project, in the development of a coupled storm-resolving earth system model operating with a grid spacing of O(1 km) on decadal time scales and in the development of the ICON large-eddy model version (ICON-LEM). Our interests in how the surface influences convection naturally extends to the dynamics of that surface, bringing the group closest to the other departments.  This brute-force modelling strategy is paired with the application of storm-resolving simulations of radiative convective equilibrium (RCE) to problems of climate, a useful conceptualization to investigate interactions between convection, the surface and its spatial distribution. It is also paired with the design and execution of field campaigns, such as FESSTVaL in Germany or BOW-TIE in the tropical Atlantic to obtain highly resolved measurements of the near-surface air and the underlying surface.

 

Since 2011, the group benefits of a preferential contact with and support from the German Weather Service via its involvement in the Hans Ertel Centre for Weather Research