AREM AND ITS SIMULATIONS ON THE DAILY RAINFALL IN SUMMER IN 2003

Facing significant effects of the Tibetan Plateau and many other steep mountains on the weather,especially on the precipitation in China,a regional Eta-coodinate model (REM) has been developed since 1980s and the REM has been popularly used not only to the summer precipitation predictions and the heavy rainfall studies butalso to related simulation studies in hydrology and environment in China since 1990s.According to distincta-tmospheric circulation and complex terrain features in China and learning from the current state-of-art smodels,such as,NCEP Etamodel,MM5,AR PS,IAP-model,CMAHLAFS,et al.,REM was paid muchattention on handling topography,moisture advection and minimizing artificial diffusion.Because of well handling with topography and water vapor trans-portation,the REM has shown it sgreat capabilities in capturing major features of precipitation in the Eastern China,including the distribution of summer rain belt,heavy rainfall intensity and maximum rainfall location.Based on the REM sframework,anadvanced REM (AREM) has been developing under cooperation with other institutes in recent years,which includes increasing resolut ions in vertical and horizontal and updating physical parameterizations.The horizontal resolution could reach about 18 km.In the vertical,the model could be unevenly divided into 32 layers.The main physical process in A REM consists:(1) explicit prediction scheme in cloud and precipitation;(2) modified Betts convective adjustment scheme;(3) nolocal PBL paramet erization scheme;(4) a two-step shapepreserving moisture advection scheme.Inaddition,from REM to AREM,many attentions are paid to the coding standardization and modularization.The preliminary version of AREM has beingused to study and predict the heavy rainfalls along the Yangtze River reaches.Realtime used predict ions in Hunan,Hubei and Anhui provinces in recent years show the great capabilities of AREM in forecasting the heavy rainfall events over most of China region.Case studies show that the AREM captures reasonable structures and evolutions of the rainfall systems along the Yangtze River.In this study,the capability of the AREM in predicting summer precipitation features over the Eastern China was shown by reproducing the summer rainfall from June 1 to August 30 in 2003.The AREM captures well notonly the southnorth movement of rainbelt,butalso the mean precipitation dist ribution and rainfall centers,in the summer of 2003.