河南省集中降水时段中期天气分析

The Medium Range Weather Analysis on Tight Precipitation Period in Henan

2003年8～9月、2004年7～8月河南省降水异常偏多.利用1985～2004年7～9月历史候图格点资料,对2003、2004年7～9月逐候500hPa图和同期历史平均图进行对比分析,同时对影响2003、2004年7～9月集中降水时段的500hPa图上中高纬度形势场、西太平洋副热带高压活动、西风环流指数、强集中时段的暴雨出现的环流特征等进行分析.结果表明:河南省集中降水时段出现在长波调整期;极涡中心从东欧北部东移或从北美洲北部西退预示着河南省降水时段开始,且极涡中心在中西伯利亚高原北部稳定,使降水时段维持;副高脊线的进、退和脊线稳定在28°N附近是降水稳定维持的条件;亚洲中纬度西风偏弱、东风偏强是产生强降水的条件;集中降水时段出现在低环流指数的波动期.

The weather was singularly wet during Aug-Sep 2003 and Jul-Aug 2004 in Henan. Based on the historical pentad grid point data, the circulation of every pentad at 500hPa during Jul-sep 2003 and 2004 and the historical average charts at the corresponding period were contrasted and analyzed. The circulation pattern of middle and higher latitudes,the activities of west pacific subtropical high at 500hpa,the westerly circulation index and the characteristics of the circulation during the tight rainstorm time were studied. The results show that the tight rain period accords with the time when long-waves adjust; the phenomena that the core of the polar vortex moving eastward from the north of the eastern Europe and withdrawing from the north of the northern Africaare the indication of the beginning of the tight precipitation period, and the stabilization of the core in the north of the middle Siberian plateau can keep the precipitation in Henan; the marching and withdrawing of the ridge line of subtropical high and the stabilization of the ridge line near 28N are the conditions of the lasting of precipitation; weaker west wind and stronger east wind are the conditions that strong precipitation comes into being; the tight precipitation time appears during the period when low circulation index waves.