The summer drying problem over south-eastern Europe: Sensitivity of the limited area model HIRHAM4 to improvements in physical parameterization and resolution

This study concentrates on the too dry and too warm simulation of climate over south-eastern Europe during the summer. This is a special model feature that is typical for many regional climate models, and also to a lower extend visible in GCMs. Here, the HIRHAM4 atmospheric high resolution limited area model is considered using prescribed SSTs and lateral boundary conditions determined from ECMWF re-analysis data. In former studies it was indicated that the warm and dry bias cannot be explained by systematic errors in the large scale general circulation.In order to analyse this model deficit, several sensitivity tests and climate simulations were performed using different versions of HIRHAM4. A model area was chosen that covers central and south-eastern Europe at a 50 km resolution. As a typical year, 1990 was chosen as integration period. These experiments include also a very high resolution simulation using a resolution of 25 km on the same area. This paper presents an excerpt of the investigations performed with a focus on the Danube catchment.