Abstract : Q.2
Evaluation of convection-resolving model simulations with the COSMO-Model in mountainous terrain

Jörg Trentmann, Heini Wernli, Ulrich Corsmeier, Jan Handwerker, Martin Kohler
Institute for Atmospheric Physics, University Mainz

Convective precipitation accounts for most of the summer precipitation in South-West Germany and can lead to significant monetary losses due to hail and/or wind gusts. The need for accurate forecasting of convective events motivated the development of high-resolution numerical weather prediction models like the LMK, WRF, and AROME. Especially the explicit treatment of deep convection is expected to lead to a significantly improved model performance during convective situations in summer. These high-resolution model results allow a process-based evaluation of the model performance also under convective conditions, since most scales of the atmospheric flow are explicitly resolved.

We conducted model simulations using the Local Model (LM) of the German Weather Service (DWD) with a horizontal grid point distance of approx. 2.8 km and without the parameterization of deep convection. Here, we present model results for 12 July 2006, when local single convective cells were initiated in the Black Forest region in South-West Germany that lasted about 2 hours. Detailed observations of the atmospheric conditions were obtained before, during, and after the convective event within the PRINCE (Prediction, identification, and tracking of convective cells) field experiment, a testrun for the COPS experiment in 2007. Available measurements include radio sondes, cloud and precipitation radar, lidar, and mobile radio sondes.

The model results will be evaluated with the field observations. Special focus will be given to the boundary layer structure and their temporal and spatial variation. The processes that lead to the initiation of convection in the model will be evaluated and compared with observations. Using high-frequency model output, the initiation and evolution of a single convective cell in the model will be analyzed. These investigations allow a detailed evaluation of the model simulations under convective conditions in mountainous terrain.