台风“莫拉克”影响期间浙江大风成因分析

利用常规资料、浙江省自动站加密资料、NCEP/NCAR1°×1°每日4次再分析资料和多普勒天气雷达资料对2009年第8号台风“莫拉克”影响期间浙江大风的成因进行了分析。此次台风大风影响具有影响时间早、持续时间长、影响范围大和大风强度强的特点。副热带高压快速加强西进是造成台风大风提早出现的主要原因之一。鞍型场、3个台风相互影响使得“莫拉克”台风移速减慢，导致台风大风对浙江沿海的影响时间增长。“莫拉克”登陆福建后其西北侧华北高压以及东南侧海上高压的存在使得地面气压梯度维持，导致大风影响时间增长和影响范围增大。垂直方向环流将高层动量下传导致低层风速猛增。多普勒天气雷达径向速度产品VCP21进行速度退模糊后可以作为台风大风分布范围和极大风速预测的一个参考依据，预测时其在沿海海面效果要较内陆好。

Causal Analysis of Strong Wind Weather in Zhejiang Induced by Typhoon Morakot

An analysis is made of the causes of strong wind weather in Zhejiang during the typhoon Morakot by using the conventional radiosonde, automatic station, NCEP/NCAR 1°×1° reanalysis, and Doppler radar data. Results show that strong winds had the characteristics of early influence, long duration, wide scope, and strong intensity. The strengthened and westward moved subtropical high is the main cause that made the strong wind appear earlier. The typhoon moved slowly, which was caused by the saddle field and the interaction of three typhoons, leading to the persisting strong wind. The maintenance of pressure gradient is the cause of earlier and wider strong wind influence. The analysis indicates that the downward transport of high level momentum and the downward moving wind speed center enhanced the surface winds. The velocity products of Doppler radar can also be used as important references for forecasting extreme wind speeds in typhoons.