两次西行热带气旋影响云南的诊断分析

Diagnostic Analysis of Two Westbound Tropical Cyclones Affecting Yunnan

运用中央气象台台风实时业务定位数据、云南省124个国家气象站降水实况和NCEP再分析资料(水平分辨率1°×1°,时间分辨率逐6 h),对比分析了1213号台风启德和1309号强热带风暴飞燕影响云南的路径、环流场、云图、水汽条件、动力条件等特征。结果表明:"启德"影响云南期间青藏高压位置偏西,副热带高压呈带状,热带气旋(TC)位于副热带高压西南侧的东南风到偏东风中,引导气流有利于台风取偏西路径影响云南。而"飞燕"影响时青藏高压位置偏东,副热带高压呈块状,TC位于副热带高压西侧的偏南风中,引导气流有利于热带低压取西北路径影响云南,从而使得"飞燕"影响时云南中部处于气旋性风场中,西南气流和副热带高压外围偏南气流两支气流汇集在此,在云南中部也产生了较强降水。两个TC影响云南时对流层中低层保持了较大的水汽输送。水汽主要来自于其本身、南海洋面和孟加拉湾。水汽辐合中心处于低压倒槽的槽前,随着系统自东向西影响云南的中部及以南地区。强降水区低层辐合、高层辐散,强上升运动为降水提供了有利的动力机制,释放了不稳定能量。因此,做好青藏高压和副热带高压的形态、位置的预报有利于把握登陆后热带低压的移动路径,从而准确预报降水强度和落区。

The real-time typhoon subjective positioning data from National Meteorological Centre,precipitation observation data from 124 national weather stations in Yunnan Province and the NCEP reanalysis data with 1.0°×1.0° horizontal resolution and 6 h temporal resolution are used to analyze the influence of No.1213 TC 'Kai-tak' and No.1309 TC 'Jebi' on Yunnan.The characteristics of the tropical cyclone(TC) moving path,circulation field,cloud,water vapor,dynamic conditions are analyzed.The results show that while 'Kai-tak' influences Yunnan,the position of Qinghai-Tibet high pressure is by west and the subtropical high is zonal.TC lies in the southeast to easterly wind of the southwest side of the subtropical high,so the path of TC is the west path.But when 'Jebi' affects Yunnan,the position of Qinghai-Tibet high pressure is by east and the subtropical high is massive.TC is in the southerly wind of the west side of the subtropical high,so the path of TC is the northwest path,and the central part of Yunnan is in cyclonic wind field where the southwestern airflow and the subtropical high periphery south airflow gather creating heavy rainfalls there.When the two TCs affect Yunnan,the lower troposphere has a larger transport of water vapor.The water vapor mainly comes from TC,the South Sea of China and the Bay of Bengal.Moisture convergence center is in the front of the low pressure inverted trough,impacting the central and southern part of Yunnan from east to west along with the weather system.Heavy precipitation zone has convergence in lower level and divergence in higher level.Strong upward motion provides favorable dynamic mechanism for precipitation and releases unstable energy.Therefore,the forecasting of the shapes and positions of the Tibetan high and subtropical high is beneficial to forecasting the moving path of tropical low after its landing so that the forecast of rainfall intensity and location can be more accurate.