Based on NCEP 2. 5° × 2. 5°reanalysis data of wind and daily station precipitation data from 1998 to 2008,a regular pattern is found that when there is a heavy rain in Shanghai, 10-20 day LFO zonal wind along 30° N in East China becomes stronger than normal and there is 10-20 day LFO southerly wind in Fujian and Zhejiang coastal area at the same time. So define the two areas as influencing areas. After doing lag correlation analysis with 10-20 day LFO wind in whole field and 10-20 day LFO zonal and meridional wind of the two influencing areas separately,two key areas are found,which are area 110°-130°E,0°-10°N and area 160°-140°W,45°-55°N respectively. It is found that 10-20 day LFO zonal wind propagates from area 110°-130°E,0°-10°N to the region around Shanghai and 10-20 day LFO meridional wind propagates from area 160°-140°W,45°-55°N to Shanghai. Therefore through LFO propagation, 10-20 day LFO wind of the two key areas would influence the weather of Shanghai area. Results also show that 10-20 day LFO zonal wind and 10-20 day LFO meridional wind of the two key areas have a good relationship with precipitation of Shanghai 15-20 days later. Prediction test shows that the 10-20 day LFO wind in the two key areas can be good indicators of extended range forecast of summer precipitation in Shanghai.%利用1998-2007年上海站降水资料和NCEP逐日700 hPa再分析风场资料,通过统计分析,发现上海强降水发生日,在10～20天滤波的合成低频流场上,我国沿海30°N附近地区纬向风明显加强,浙江福建沿海地区为一致的偏南风,故定义这两个区域为影响区.通过单点相关方法,在10～20天滤波的经纬向风场上分别找到一个与影响区风速超前15～20天相关性好的关键区域:110～130°E,0°～10°N和160～140°W,45～55°N.研究表明,关键区域的10～20天低频经纬向风有明显向上海附近地区传播的趋势,并且与15～20天后上海降水有显著正相关,对上海市6-8月未来15天的降水有较好的指示作用.
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