CLIMATIC CHARACTERISTICS OF RAINSTORM ASSOCIATED WITH INVERTED TROUGH OF TROPICAL CYCLONE IN ZHEJIANG PROVINCE

DONG Mei-ying; CHEN Feng; XU Luan; YANG Cheng; QIU Jin-jing

doi:10.16032/j.issn.1004-4965.2017.01.009

Abstract：Based on the past 40 years of daily rainfall data of tropical cyclones and their best track observations from Shanghai Institute of Typhoon of China Meteorological Administration (CMA),climatic characteristics of rainstorms associated with inverted troughs of tropical cyclones (for brief,called RIT below) in Zhejiang province are investigated in this paper by statistical and weather analysis methods.Results are showed as follows:(1) On average,there are 1.8 times of RIT each year,which account for 41％ of total tropical cyclone rainstorm frequency and thus RIT is an important form of tropical cyclone rainstorm in Zhejiang province.Most of RIT happens from August to September and in coastal areas from the southern Ningbo city to Wenzhou city.Moreover,strong precipitation centers are usually located in coastal regions from Taizhou city to Wenzhou city;(2) Tropical cyclones which induce RIT mostly make landfall on the coastal regions from the eastern Guangdong province to the southern Zhejiang province,with northward then recurvature tracks or northwestward tracks over land.On the days of landfall,the RIT most likely occurs and has the strongest rainfall intensity.During the burst period of RIT,tropical cyclones are usually in the region from the coast of middle Fujian province via Taiwan Strait to northeast Taiwan Island;(3) The asymmetric distribution of maximum RIT relative to tropical cyclones is prominent,with high probability in the regions of north-northeast azimuth and the ring between 2.5 and 5.0 degrees of zonal distance from the tropical cyclone center.However,the maximum of RIT intensity appears in tropical depressions and is often located in the east-northeast azimuth.The extreme precipitation events mainly relate with the interaction between tropical cyclones and periphery systems such as western north Pacific subtropical highs,resultant easterly jets and strong convergence near the tropical cyclone inverted troughs,as well as active mesoscale deep convection in the east-northeast azimuth of tropical cyclones.