2007年6—7月西太平洋副热带高压的异常特征及其成因分析

采用NCEP资料以及NOAA卫星观测的OLR场资料,分析了2007年6—7月淮河流域暴雨及江南、华南异常高温期间西太平洋副热带高压的异常特征,其表现为强度强且南北位置相对稳定,东西方向进退明显于南北方向的移动。通过分析经圈平面上的垂直环流及风矢量场的特征表明,副高南北两侧都存在一定强度的上升气流,北侧上升气流对西太平洋副高中心区700 hPa以上高度的下沉运动有激发作用,而南侧上升气流对西太平洋副高中心区的下沉运动作用不大。中高纬度阻塞高压双阻型的建立,有利于西太平洋副高的加强和发展。强劲而稳定少动的中纬度西风急流和热带地区异常活跃的对流均有利于西太平洋副高的相对稳定。

Abnormal Characteristics of Western Pacific Subtropical High from June to July 2007 and Analysis of Its Causes

Based on the NCEP data and outgoing longwave radiation (OLR) data provided by NOAA satellite observations, the paper analyzed the abnormal characteristics of western Pacific subtropical high (WPSH) during the storm rainfall over the Huaihe Valley and abnormal high temperature in the south of China from June to July in 2007. It is shown that the WPSH is stronger than normal and relatively stable in the north south movement.The shift in the east west direction is more obvious than in the south north direction. By analyzing the characteristics of vertical circulation field and wind vector on meridional plane, we find that the upward currents can be stimulated in the south and north of WPSH. The upward current in the north of WPSH stimulated the downward current in the center of WPSH at 700 hPa over the region. While the upward current in the south of WPSH plays a minor role on the downward current in the center of WPSH.The establishment of a blocking anticyclone in the mid higher latitude can intensify the WPSH. The strong and stable westerly jet in the middle latitude and the abnormal actively convection in the tropical region are conducive to the relative stability of the WPSH.