南海台风“韦帕”生成环境条件及移动转向成因分析

Analysis on the formation environmental conditions and causes of movement and recurvature of Tropical Storm Wipha

利用华南区域常规观测站资料、静止卫星红外云图及NCEP格点再分析资料,对2019年第7号台风"韦帕"生成环境条件、移动转向的成因进行了分析。结果表明,台风"韦帕"生成于热带辐合带弱垂直风切变中心附近,高海温是其生成及发展的基础条件,强度维持与西南季风及越赤道气流卷入密切相关。感热通量和潜热通量变化显示,"韦帕"所获取的海表面热通量较少,这是其强度增强有限的主要原因;台风移动路径与引导气流密切相关,其不同阶段受不同层次引导气流影响,且引导气流弱,台风移动速度也较慢;台风"韦帕"发生停滞及转向,主要由于大尺度环境场发生明显改变,西太平洋副热带高压、南亚高压及东风波都起重要的影响;低层台风中心附近风速变化影响台风环流结构内力的方向大小,也会造成台风路径移向的变化,高层辐散区对台风中心移动有"引导"作用。

Based on the data of conventional observation stations in South China, geostationary satellite infrared cloud images and NCEP grid reanalysis data, the environmental conditions and causes of movement and recurvature of Tropical Storm Wipha in 2019 were analyzed. The results show that(1) Tropical Storm Wipha was generated near the weak vertical wind shear center of the tropical convergence zone. High sea temperature is the basic condition for its generation and development, and the intensity maintenance is closely related to the southwest monsoon and the involvement of cross equatorial airflow. The changes of sensible heat flux and latent heat flux show that the heat flux from the sea surface obtained by Wipha was less, which is the main reason for the limited enhancement of its intensity.(2) The movement path of a typhoon is closely related to the guided airflow, and its different stages are affected by different levels of guided airflow. The weaker the guided airflow is, the slower the typhoon moves.(3) Weipa stagnated and turned, mainly due to significant changes in the large-scale environmental field. The West Pacific subtropical high, South Asia high and easterly wave all played an important role.(4) The change of wind speed near the low-level typhoon center will not only affect the direction of internal force of typhoon circulation structure, but also cause the change of typhoon path;the highlevel divergence area can guide the movement of typhoon center.