台湾岛地形诱生次级环流系统对热带气旋异常运动的影响机制

Mechansism of the Impact of the Cyclone System Induced by the Taiwan Island Topography on Tropical Cyclone Unusual Motion

对经过中国台湾岛和海南岛、吕宋岛、日本诸岛以及朝鲜半岛的热带气旋在过岛前后的运动、结构和强度的时空变化进行了统计诊断分析。研究结果表明，台湾岛附近热带气旋运动左偏（定义为偏于以前路径的左侧）机率最大，且台湾岛周围是产生诱生低压的高频区。采用理想东、西风环境场作为数值模拟背景场，数值研究了岛屿地形强迫与台湾附近的环境流场的相互作用及其对热带气旋运动偏转的影响，提出了岛屿地形强迫、背景场和热带气旋涡旋三者相互作用对热带气旋路径突然转折影响的观点，即台湾地形有利于环境场中诱生出一对偏差偶极涡，这对诱生偏差偶极涡将导致逼近岛屿的热带气旋产生运动方向的突然偏折，且在不同基本气流条件下，岛屿地形对热带气旋运动可能产生显著不同的影响。

The present paper analyzes statistically the temporal and spatial variation of the movement, structure and intensity of the tropical cyclone (TC) before and after it passes Taiwan Island, Hainan Island, Luzon Island, the Philippines, Islands of Japan and Korea Peninsula The result shows that the left-turning (deviate to the left of pre-track) probability of TC motion is the largest around Taiwan Island Furthermore, Taiwan is a high-frequency area to occur the induced cyclone Using the numerical simulation in which the ideal easterly and westerly wind are considered to be the background field, this paper studies the interaction between the island topographical forcing and the environmental flow field around Taiwan Island and its impact on the turning of tropical cyclone The results show that the interaction among island topographical forcing, environmental field and tropical cyclone vortex has influence on the sudden turning of the tropical cyclone track Thus the Taiwan topography has the positive effect on inducing a dipole difference vortex in the environment field, which will result in the sudden turning of the motional direction of tropical cyclones of approaching the island Besides, the island topography has significantly different effects on tropical cyclone motion under different basic flow conditions