2001年7月下旬河南连续性强降水中期天气特征

The Medium Range Weather Character of Henan Continuous Rainstorm during July 21～31, 2001

从大尺度环流形势场、西风环流指数、阻塞高压、副热带高压和南亚高压等方面 ,对 2 0 0 1年汛期强降水多发时段的中期天气特征进行了分析 ,结果表明 :①极涡由一个中心分裂为多个中心 ,北半球极涡呈偶极型或多极型 ,其中有一较强中心位于东半球偏于亚洲一侧 ;②亚欧中高纬环流形势为两脊一槽型 ,亚洲中部为一低压槽 ;③连续性强降水发生在西风环流指数由峰值向谷点过度的过程中 ;④鄂霍次克海阻塞高压的建立是造成我省连续性强降水的关键 ;⑤西太平洋副热带高压在短时间内迅速西伸北跳 ,14 0°E副高脊线位置位于 30°N附近并稳定 ;⑥10 0hPa南亚高压脊线北跳至 33°N以北 ,且中心位置自西向东震荡并稳定于

Analyzing the large-scale circulation, westerly circulation index, barrage high, subtropical high and south Asia high, we concluded the medium range characters during flood season, as following: ① The polar vortex can be split into several centers from one, and the stronger center is at east hemisphere.② Europe-Asia circulation position between middle and high latitudes, is two ridges-one trough, there is a low trough in the middle of Asia.③ Continuous rainfall took place, during westerly circulation index transform from front to the lowest point.④ Okhotsk barrage high is the important reason of our province's rainfall.⑤ Subtropical high over west pacific is moves westwards during short time, this is benefit to the development of south-west current and the deliver of vapor.⑥ The center of 100hPa south Asia high can give indication to forecast of rainfall.