Evaluation of RegCM simulation ensemble using different parameterization scheme combinations: a case study for an extremely wet year in the Carpathian region

Abstract

AbstractDue to its high influence on agriculture, infrastructure, water management, and other areas, precipitation is one of the most important climate factors. However, it is still challenging for climate models to realistically reproduce regional patterns, temporal variability, and precipitation intensity. This is especially true for extreme conditions and terrains with heterogeneous orography, like the Carpathian region.For the sake of quantifying the uncertainty and improving the accuracy of the precipitation simulations of the RegCM4.7 regional climate model over the Carpathian region, we evaluate the performance of different options at 10 km horizontal resolution, using ERA-Interim reanalysis data as initial and boundary conditions. Altogether 24 simulations were carried out by using various combinations of the physical schemes (2 land surface, 2 microphysics, 3 cumulus convection and 2 planetary boundary layer (PBL) schemes) for the year 2010, which was the wettest year in the Carpathian region (especially in Hungary) since 1901. Different parameterization combinations lead to different simulated climates, so their variance can serve as an estimate of model uncertainty due to the representation of unresolved phenomena.The results show that RegCM is sensitive to the choice of scheme combinations. The analysis of the RegCM4.7 ensemble indicates systematic precipitation biases, which are linked to different physical mechanisms in the summer and winter seasons. Based on the results, RegCM4.7 is the most sensitive to the applied convection scheme, but the interactions with the other schemes (e.g., land surface and microphysics) affect the convective and large-scale precipitation in addition to the total precipitation.