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 o ver 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 exte nd visible in GCMs. Here, the HIRHAM4 atmospheric high resolution limited a rea model is considered using prescribed SSTs and lateral boundary conditio ns determined from ECMWF re-analysis data. In former studies it was indicated that the warm and dry bias cannot be exp lained by systematic errors in the large scale general circulation.In order to analyse this model deficit, several sensitivity tests and climate simul ations 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 experiment s include also a very high resolution simulation using a resolution of 25 k m on the same area. This paper presents an excerpt of the investigations pe rformed with a focus on the Danube catchment.