Assessing the sensitivity of RegCM4 to cumulus and ocean surface schemes over the Southeast Asia domain of the coordinated regional climate downscaling experiment

Abstract

Multi-year experiments are conducted using the most recent version of the Abdus Salam International Centre for Theoretical Physics regional climate model RegCM4 (version 4.7) to customize its performance over Southeast Asia — a region with few RCMs applied to date. The model is driven by ERA-Interim reanalysis data at a grid spacing of 25 km using the CORDEX (Coordinated Regional Climate Downscaling Experiment) Southeast Asia domain. The authors focus on comparing the convection schemes of Emanuel and Tiedtke (Tiedtke-1) and Tiedtke with effects of sea surface evaporation introduced (Tiedtke-2). The authors find that, for temperature over land, the model shows reasonable performance in reproducing the present-day climatology in both December–January–February (DJF) and June–July–August (JJA) in all the experiments. Meanwhile, cold biases prevail in both seasons, although portions of warm bias exist in DJF. For precipitation, the spatial pattern and amount, as well as seasonal evolution, are in general reproduced well in the experiments. Better performances of Tiedtke-1 and Tiedtke-2 are evident compared to Emanuel, particularly over ocean. Thereby, the optimal configuration of RegCM4.7 for future climate change simulations over the region is identified as using the Tiedtke scheme with spray effects considered, along with the default settings for other physical parameterizations.

Keywords

• regcm
• coordinated regional climate downscaling experiment
• convective scheme
• southeast asia