1998年二度梅雨期西太平洋副热带高压活动的诊断分析

A DIAGNOSTIC ANALYSIS OF ACTIVITIES OF THE WESTERN PACIFIC SUBTROPICAL HIGH DURING THE SECOND MEIYU PERIOD IN 1998

文章对 1 998年长江流域二度梅雨期西太平洋副热带高压的活动与大气经圈环流的关系进行了分析。结果指出 ,副高的进退与经圈环流的调整有着密切的关系。副高的北跳并不是由与其相联系的反环流下沉支直接北移所引起的。低纬度深厚上升运动的发展不利于副高维持在较低的纬度 ,而中纬度反环流的突然向南调整则有利于副高在更北的纬度建立 ,于是副高出现突然北跳的现象。它是江淮地区出梅的一种经圈环流调整形式。副高在稳定期间 ,随着与它相联系的反环流的南北运动而作相应的南北运动。副高在南退之前 ,对流层顶附近有反环流生成 ,然后迅速向南运动 ,副高也随之迅速南退。

The relationship between atmospheric meridional circulation and activities of the Western Pacific Subtropical High during the second Meiyu period in 1998 over the Yangtze River is analyzed. The results show that the advance and retreat of the Western Pacific Subtropical High are closely connected with the variation of the meridional circulation. The northward jump of the Western Pacific Subtropical High is not directly caused by the northward movement of the descending branch of the counter-circulation, which is connected with the Western Pacific Subtropical High. The development of the deep ascending motion at the lower latitudes obstructs the maintaining of the Western Pacific Subtropical High in the lower latitudes. Whereas, the sudden southward movement of the counter-circulation at the middle latitudes is in favor of the buildup of the Western Pacific Subtropical High in the farther north latitudes. Then, the Western Pacific Subtropical High jumps northward abruptly. This is a form of the re-adjustment of the meridional circulation that ends Meiyu in the Yangtze-Huai River Region. The Western Pacific Subtropical High moves northward or southward along with the connected counter-circulation while remaining steady. Before the Western Pacific Subtropical High retreats from north, a new counter-circulation originates near the tropopause. When the new counter-circulation moves south rapidly, the Western Pacific Subtropical High moves south along with it.