Sensitivity analysis of RegCM4 model: present time simulations over the Mediterranean.

The sensitivity of RegCM4 to different physics parameterizations is being investigated in this study. It is the first part of an attempt to find the most optimal combination of configurations to "run" RegCM4 for the area of study. The spatial resolution of the model is 25 × 25 km. The performed simulations include changes in the model's convection, atmospheric boundary layer, and ocean flux schemes for the period 1981–1990 in the Mediterranean region. The simulations were forced by ERA-Interim data for the initial and boundary conditions (ICBC) and sea surface temperature (SST). The processing of the different simulated data was performed on a seasonal basis. For a detailed evaluation of the changes, the domain of study was divided in five smaller areas derived from the EURO-CORDEX analysis domain. E-OBS data were used to validate RegCM4. It has been found that UW-PBL scheme presents a negative bias regarding atmospheric boundary layer thickness and temperature, and it reduces the wet/dry biases of Holtslag PBL scheme. Additionally, BATS1e Monin-Obukhov scheme increases both precipitation and temperature. Regarding cumulus convection schemes, Grell scheme is characterized by a reduction of convective precipitation, while total precipitation increases mainly in the windward side of mountainous ranges. This scheme also presents a cold bias. Wind speed, in the case of Grell and UW-PBL schemes, presents a reduction in continental areas, while a reinforcement of the Etesian winds is evident in Aegean Sea. [ABSTRACT FROM AUTHOR]