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《Acta Meteorologica Sinica》 2006-02
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THE IMPACT OF 30-60 DAY OSCILLATIONS OVER THE SUBTROPICAL PACIFIC ON THE EAST ASIAN SUMMER RAINFALL

Han Rongqing~1 Li Weijing~2 Dong Min~21 Nanjing University of Information Science and Technology,Nanjing 2100442 National Climate Center of China Meteorological Administration,Beijing 100081  
The relationships between the precipitation over Eastern Asia(20°-45°N,110°-135°E) and the 30-60 day intraseasonal oscillations(ISO) over the boreal Pacific during the summer are studied.The daily wind and height fields of NCEP/NCAR reanalysis data and the 24 h precipitation data of China 687 stations during 1958-2000,and the pentad precipitation of CMAP/NOAA from 1979 to 2002, are all analyzed by the Space-time filter analysis.The analysis results,from every drought and flood summer for 4 different regions of East Asia respectively during 1958-2000,showed that the precipitation amount in the East Asian summer monsoon region is well correlated to the westward propagation of 30-60 day ISO via the north central-eastern Pacific,and depends little on the intensity changes of the East Asian summer monsoon.And the westward ISO is usually the low-frequency low and high pressure systems from the Bay of Alaska in northeastern Pacific and the Okhotsk in the northwestern Pacific of mid-high latitudes,and the ISO evolving in subtropical easterlies.In mid-high latitude the phenomena are related to the westward propagating mid-ocean trough and block high backing off.Therefore the westward propagating ISO from the north central-eastern Pacific to East Asia is indispensable to sufficient rainfall occurring for East Asia in summer, which is resulted from long-wave adjustment process in the mid-high latitudes and ISO evolving in tropical easterlies.
【Fund】: 国家自然科学基金项目(40375025);; 国家自然科学基金项目(90211011)
【CateGory Index】: P462.4
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