台风“布拉万”路径和强度的诊断分析

Abstract

利用日本气象厅的热带气旋最优路径数据和多种卫星再分析资料，本文对1215号台风“布拉万”移动路径和强度变化的主要影响因素进行了天气学诊断分析。在台风生命史内，“布拉万”呈反气旋式移动，其方向与500 hPa流场的引导气流方向基本一致，是副热带高压、西风槽及双台风共同作用的结果。在“布拉万”发展初期，高海温、弱的水平风垂直切变以及对流层中低层强烈的辐合上升运动使其逐渐达到了生命史中最大强度。随后，低海温和较强的垂直切变使台风结构遭到破坏，低层台风中心的辐合上升运动减弱。同时，“布拉万”移入西风槽，强冷空气入侵，台风逐渐减弱衰退。 Best-track data from the Japan Meteorological Agency and reanalysis datasets from the multi sa-tellite altimeters are analyzed during the lifetime of the No. 1215 typhoon “Bolaven”, using the synoptic analysis. Main influence factors for the variations of typhoon’s path and intensity are diagnosed in this paper. During the whole lifetime, typhoon “Bolaven” gradually changes its direction. This movement is mainly guided by the subtropical high, westerlies as well as the typhoon “Tembin”. The strengthening of typhoon “Bolaven” is consistent with the higher sea surface temperature and lower vertical wind shear. Besides, typhoon’s convergence and upward motions in the middle and lower troposphere also can promote this enhancement. As a result, “Bolaven” reaches its maximum intensity. Subsequently, due to the decrease of the sea surface temperature and the increase of the vertical wind shear, typhoon’s structure is destroyed. Meanwhile, the corresponding convergence and upward motions are weakened at low levels. Coupled with the strong cold air advection by the westerly trough, all these adverse factors lead to the “Bolaven” weakened.