上海市夏季降水延伸期的预报方法

A study on extended range forecast method for summer precipitation in Shanghai

利用1998—2007年上海站降水资料和NCEP逐日700hPa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.

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.