南北半球台风形成的物理场特征对比分析

AN ANALYSIS ON PHYSICAL FIELDS IN THE GENESIS STAGE OF TROPICAL CYCLONES IN SOUTHERN AND NORTHERN HEMISPHERE

关键词:  南北半球  台风生消  低层辐合

Key words:  southern hemisphere and northern hemisphere  tropical cyclogenesis and tropical cycloysis  low level convergence

摘要:

以南半球7619热带风暴和北半球8111号台风为例,对台风生成前后台风生成区附近的低空大尺度纬向流场的变化及越赤道气流强度的变化进行分析和计算,并对台风生成区大气层结的温湿场分布、大气低层涡度场的逐日变化和对流层上下层的风垂直切变场逐日变化进行计算。同时进行南北半球台风对比分析,找出了南北半球台风生消时段大尺度环流和台风生成区大气物理场的共同特征和相同的天气变化机制,分析表明台风生成的决定性因素是低层大尺度流场对台风生成区辐合的加强,致使水平切变急剧增大的结果。由此提出一个生消诊断公式,讨论了用天气学方法定量预报台风生消的可能性。

Abstract:

Based on the cases of the southern hemisphere tropical cyclone 7619 and the northern hemisphere tropical cyclone 8111, the variations of low level large scale zonal wind field and the intensity of the crossing-equator wind in the two different original zones of tropical cyclone 7619 and 8111 are calculated. The day-day variations of low level vorticity field and the vertical wind shear fields in troposphere, and the stratified thermo-hygro fields are calculated too. Although the two tropical cyclones are from different hemisphere but their atmosphere physical fields and synoptic situations show some common characteristics in the beginning and ending stages. It is indicated that as the low level large scale streamline convergence in the tropical cyclone original zone is intensified, the horizontal wind shear becomes big quickly which is the main cause for tropical cyclogenesis. A diagnostic formula is provided and the predictability for tropical cyclogenesis and tropical cyclolysis by the way of synoptical quantiative analysis is discussed here.