江淮梅雨异常的大气环流特征

Analyses on the General Circulation Characteristics of Meiyu over the Changjiang-Huaihe Valley

江淮梅雨是我国夏季风雨带向北推进期中的一个重要阶段。利用江苏省气象局提供的江淮地区1954-2001年人梅日期、冉梅日期和梅雨量资料，详细讨论了江淮梅雨丰、枯梅年同期大气环流的差异。结果表明：丰梅年高层100hPa南亚高压呈纬向分布，高压强度增强。中层500hPa极涡强度增强，乌拉尔山高压脊强度增强，鄂霍茨克海阻塞高压强度增强，蒙古高压增强，东亚大槽位置较常年偏东偏南，120°E副热带高压脊线位于20°～25°N之间。低层850hPa南半球越赤道气流抵达北半球后向北偏西方向伸展，与来自阿拉伯海、盂加拉湾的西南气流和副热带高压西南侧的东南气流在南海北部汇合，在我国江淮流域形成一条准东西向的强风速辐合带，一直延伸到国际日界线附近。丰梅年低层辐合增强，高层辐散增强，高低层抽吸作用增强，垂直运动增强，对流旺盛，有利于梅雨的异常偏多；枯梅年则反之。

The Meiyu over the Changjiang-Huaihe valley is the important constituent part of summer rain band in China. Based on the onset date, the end date and the precipitation of Meiyu characteristic data over the Changjiang-Huaihe valley from 1954 to 2001 provided by Jiangsu Meteorological Administration, the general circulation characteristic of the Meiyu is studied. The results show that there are significant difference characters of general atmospheric circulation in the corresponding period between the high Meiyu year and low Meiyu year. The motion of subtropical ridge line at 120°E located between 20°～25°N. The precipitation of Meiyu is marked increasing （decreasing） over the Changjiang-Huaihe region, which is responsible for the south Asia high is weaken （amplification） and intensity of polar vortex, subtropical west- erly jet, equatorial easterly jet, intensity of subtropical high, water-vapor transfer of the air current spanning the eqator in the Southern Hemisphere and southwest air flow from the subtropical high westerly, the intensity of convergence over the Changjiang-Huaihe, pumping action in the altitude-low level, ascending motion and convective activity are amplification （weaken）, and vice versa.