热带气旋大风风圈半径非对称性特征及成因简析

Analysis on the asymmetric characteristics and causes of the wind circle radius of tropical cyclones

为进一步完善热带气旋大风风圈的分析和预报业务,利用中央气象台(NMC)发布的热带气旋报文资料、ERA5再分析资料,研究了2015年6月30日至2020年12月31日热带气旋最大强度时的7、10和12级风圈的非对称性特征及成因。统计结果表明:热带气旋的7级风圈半径非对称性最大,10级次之,12级最小;非对称分布热带气旋的7、10和12级风圈最大半径大多分布在东北、东南和西北象限;同一热带气旋的7级和10级风圈最大半径大多分布在相同的象限。将7级风圈单一象限分布的热带气旋与多象限分布的热带气旋各按象限分布分成4类,分析4类7级风圈单一象限分布的热带气旋生成季节、地面10 m风特征及风圈非对称分布的成因发现:各类热带气旋具有明显的季节特征;地面10 m风场呈不对称分布;风圈非对称分布与西太平洋副热带高压、西南气流及地面冷高压等天气系统与热带气旋的相互作用造成的各象限位势高度梯度非对称分布密切相关。

To improve the analysis and forecast of tropical cyclone(TC) wind circle, the asymmetric characteristics and causes of wind circle maximum radii of 55.6 km/h, 92.6 km/h and 118.5 km/h for TCs at their maximum intensity during 30 June 2015 to 31December 2020 are studied using the TC data released by the National Meteorological Centre(NMC) and data extracted from ERA5reanalysis. Statistical results show that the 55.6 km/h wind circle radius of TC is the most asymmetric, followed by the 92.6 km/h and118.5 km/h wind circle radii. The 55.6 km/h, 92.6 km/h and 118.5 km/h wind circle maximum radii of TC with asymmetric distribution are mostly located at the north east(NE), southeast(SE) and northwest(NW) quadrants. The 55.6 km/h and 118.5 km/h wind circle maximum radii of the same TC are roughly located at the same quadrant. Single quadrant distribution TCs and multiquadrant distribution TCs of 55.6 km/h wind circle are divided into four types according to quadrant distribution. By analyzing the generation season, surface wind and the causes of asymmetric distribution of TC with single quadrant distribution of 55.6 km/h wind circle, it is found that the generation of these four types of TC have obvious seasonal characteristics. The surface wind in different quadrants of TC shows asymmetric characteristic. The asymmetric distribution of wind circle is closely related to the asymmetry of potential height gradient in different quadrants caused by the interactions between TC and other weather systems, including the Western Pacific Subtropical High, the southwesterly air flow and surface cold high pressure, etc.