High Resolution Sensitivity Studies with the Regional Climate Model CCLM in the Alpine Region

The presented Study investigates the performance of the regional climate model CCLM operated at high resolution (10 kin grid) over the European Alpine region to find a suitable setup for long term regional climate simulations over mountainous terrain and to quantify various error sources. CCLM is run in 8 different Setups, spanning a substantial range of possible settings of the model and is driven by the ECMWF's ERA-40 reanalysis. The results are systematically evaluated focussing on 2 in air temperature and precipitation amount. The annual mean error in the entire Alpine region lies between -0.14 and -0.42 mm/d for precipitation and -0.98 and -1.44 K for temperature, depending on the model setup. By objectively defining climate subregions covering the Alpine region we also take advantage of the high model resolution to analyze subregional performance of the CCLM. It is shown that modifications of the domain size and vertical resolution have the greatest impact on the results, while altering the parameterization and numerics does not yield a significantly different Outcome.