Development of a Regional Climate Model (CREM) and Evaluation on Its Simulation of Summer Climate over Eastern China

Abstract

This paper describes and evaluates the performance of a regional climate model developed at the State Key Laboratory of Numerical Modeling for Atmospherics Sciences and Geophysical Fluid Dynamics/Institute of Atmospheric Physics (LASG/IAP). The model has been developed based on the numerical forecast model, Advanced Regional Eta-coordinate Model (AREM), of LASG/IAP. An advanced radiation package and a common land surface scheme have been included into the AREM. The new model is regarded as the Climate version of AREM and named CREM. To evaluate its performance in reproducing the summer climate over eastern China, the CREM with 37 km horizontal resolution was integrated from 1 May to 1 September of 1995-2004. The lateral boundary forcing data is derived from the NCEP-DOE (National Centers for Environmental Prediction-Department of Energy) reanalysis data at 6-h intervals. Evaluations on the model performance indicate that the CREM can reasonably reproduce the spatial distributions of climatological monthly (June, July, and August) mean precipitation and circulation over eastern China. The simulated monthly mean precipitation has high spatial correlation with the observation over central-eastern China, except with larger variability. Compared with the precipitation, both the spatial distribution and the spatial variability of geopotential height at 500-hPa and the zonal wind at 200-hPa are better simulated. The interannual variation of precipitation anomalies over central-eastern China is well captured by the model. The variation of the Meiyu front is realistically depicted except that the simulated rainbelt shifts northward in July. A case study of the 1998 flooding year suggests that the model can reproduce not only the seasonal mean precipitation and circulation, but also the temporal evolution of the rainfall and monsoon system over eastern China. In particular, the two northward-propagating intra-seasonal oscillation events are successfully captured in the simulation. The main deficiency of CREM is the overestimation of rainfall amount and the northward shift of the rainbelt, which probably results from the high frequency of rainstorms and exaggerated thermal contrast between central-eastern China and southern China.