1991年7月初江淮地区特大暴雨中不同尺度天气系统分析

ANALYSIS FOR THE DIFFERDNT SCALE WEATHER PATTERNS DURING THE HEAVY RAIN PERIOD OF JULY 1-5 1991 IN JIANG-HUAI REGION

利用水平平滑滤波方法对不同等压面上大尺度场的分析结果表明：在1991年7月1日—5日的暴雨过程中，从高层到低层青藏高原北部有一急流中心，急流中心位于40°N附近。和这次暴雨过程直接对应的急流中心位于29°N附近。1－5日这两个急流中心均稳定少动且中心风速比常年大。大范围降水区中的强暴雨中心和中低层的流场、风场辐合区以及扰动低压中心吻合较好。低层等压面上大中尺度系统相互作用项的区域平均值对700hPa中尺度系统发展的贡献最大。高层200hPa和中层500hPa贡献数值接近，高中低层大尺度系统相互作用项对700hPa中尺度系统发展的贡献具有同步性。

The horizontal filtering technique is employed to separate meso-scale field from large scale field for a case of heavy precipitation over Yang-Zi river occurred on 1 - 5 July 1991.The northern large-scale jet stream has a maximum velocity center exceeding 50m/s on 200hPa. Meanwhile, the southern jet stream corresponding to the large-scale precipitation area has a maximum wind velocity on 500hPa exceeding 20m/s. It is also found that when the meso-scale center of high field and wind vector field are nearly the same, a heavy rain center is always located. Finally, the contribution term to the development of meso-scale low on 700hPa at different Ievels are evaluated. It is found that 700hPa term is the biggest, while 500hPa and 200hPa terms have the same magnitude. They have same variation step.