The Possible Causes Of Drought And The Simulation Study In Sichuan-Chongqing Region In Summer 2006

Based on the NCEP/NCAR reanalysis monthly mean data, the 160 stations rainfall data in china , the OLR data and the calculated heat source data, the anomalies of atmospheric circulation have been analyzed in summer 2006. It is shown that the vertically integrated moisture transport from south to north in summer 2006 is weaker than normal. The West Pacific Subtropical High is stronger and shifts northwestward. There are no blocking high over Ural mountains and the Northeast Asia. The South Asia high is also stronger than normal, and it controls continuously the area over east of Sichuan and Chongqing. One reason that the west Pacific Subtropical High is stronger and shifts north is the heat sources over the Tibetan Plateau is weaker while the western Pacific warm pool is stronger. The rainfall of Sichuan and Chongqing during summer has a close correlation with the west Pacific Subtropical High, which tends to north (south) in drought(flood) years. The reason for that is similar to 2006.And then numerical simulations are made using the IPRC-RegCM .The control experiments and the anomalous heating sources over the Tibetan Plateau and the western Pacific warm pool are designed. The numerical simulations indicate that the heat sources over the Tibetan Plateau play an important role in the forming and maintaining of the atmospheric circulation. And possibly it is the main reason of causing the rainfall over its surroundings. When the heat source over the east of the Qinghai-Tibet Plateau is weaker and the heat source over the west Pacific Warm Pool is stronger, the precipitation to Sichuan and Chongqing region will increase, this is consistent with the diagnostic analysis result.