Multi-model simulations of a convective situation in mountainous terrain

Kurzfassung

The goal of the present study is to investigate the variability of simulated convective precipitation by three convection-resolving models using different setups and initial and boundary conditions. The COSMO, MM5 and WRF models have been used to simulate the atmospheric situation on 12 July 2006, when local convection occurred in central Europe under weak synoptic forcing. The focus of this investigation is on the convective precipitation in the Northern Black Forest in South-West Germany. The precipitation fields from the nine model simulations differ considerably. Six simulations capture the convective character of the event. However, they differ considerably in the location and timing of the intense convective cells. Only one model simulation captures the early onset of precipitation; in all other simulations, the onset of convective precipitation is delayed by up to five hours. All model simulations significantly underpredict the amount of surface precipitation compared to gauge-adjusted radar observations. The simulated diurnal cycles show maximum CAPE and minimum CIN values in the early afternoon. The different onset times of precipitation in the model simulations are shifted in accordance to the simulated diurnal cycles of CAPE and CIN. In the simulations with an early onset of precipitation also maximum CAPE and minimum CIN values appear early. The amount of simulated precipitation, however, does not correlate with CAPE or CIN.