菲律宾附近对流与长江流域夏季降水关系的初步研究

RELATIONSHIP BETWEEN THE SUMMER CONVECTION AROUND THE PHILIPPINE AND THE RAINFALL IN THE YANGTZE RIVER BASIN

利用NOAA提供的1979～2008年的向外长波辐射(OLR)资料对菲律宾附近对流进行分析并定义了菲律宾附近对流指数(PHCI)和菲律宾附近对流位置指数(PHCP)。根据PHCI和PHCP的变化情况,对我国长江流域的夏季降水进行了分析。结果表明:(1)不同等级的PHCI对长江流域降水有不同的影响。PHCI最弱,长江流域降水偏多,而PHCI最强易使长江中游及江淮之间降水偏少;PHCI较弱时,长江中游偏北局部地区偏多,PHCI较强时,长江流域降水偏少;PHCI微弱时使长江下游局部地区降水偏多,而PHCI微强则对长江流域降水几乎影响不大。(2)PHCP偏北偏东时,长江下游地区降水是偏少的,而PHCP偏向其他3个方向时,长江中游地区降水均偏多,其中偏南偏东方向长江下游降水也略偏多。(3)PHCP和PHCI相互关系:PHCP偏南,则PHCI是较弱的;PHCP偏北则并不变化一致,经向位置偏西则PHCI偏弱,经向位置偏东则PHCI偏强。

Using the monthly Outgoing Long-wave Radiation(OLR)data provided by NOAA during the period 1979～2008,the convection around the Philippine was analyzed and two indexes named Philippine Convection Index(PHCI)and Philippine Convection Position(PHCP)were defined.Based on the PHCI and PHCP,the relationship of the PHCI/PHCP and the summer precipitation in the Yangtze River Basin were studied.The results show that the different grades of the PHCI have different effect on the rainfall of the Yangtze River Basin.When the PHCI is the highest,the precipitation of the Yangtze River Basin is much more,but when the index is the lowest,the precipitation is less in the middle reaches of the Yangtze River and the Jianghuai Valley.When the PHCI is higher,the precipitation is more in the north of the middle reaches of the Yangtze River,but when the index is lower,the precipitation is much less in the Yangtze River Basin.When the PHCI is slightly high,it makes the more precipitation in the lower reaches of the Yangtze River,and when the index is slightly low,there makes no strong effect.The precipitation is less in the lower reaches of the Yangtze River when the PHCP is in the north and east,while in the other three directions(the north and west,the south and east,the south and west)the precipitation is more in the middle reaches of the Yangtze River.At the same time,when the PHCP is in the south and east,the precipitation is more in the lower reaches of the Yangtze River.When the PHCP is in the south,the PHCI is higher.But it is not the same variation when the PHCP is in the north.Furthermore,when the longitude position is in the west,the PHCI is higher,and vice versa.