三个登陆台风间接造成宁波大暴雨特征分析

Analysis on the characteristics of heavy rainfall in Ningbo indirect caused by three landing typhoons

利用常规观测和自动站加密观测、雷达、卫星云图及NCEP再分析资料,统计登陆福建未进入浙江而对宁波产生影响的台风,着重分析近几年预报与实况差别较大的“菲特”、“杜鹃”和“莫兰蒂”台风造成宁波强降水的原因。结果表明:此类台风1949—2016年共有82例,43.9%造成宁波局部暴雨,9.8%造成局部大暴雨,4.9%造成全市范围大暴雨,其中75%发生在2013年以后。远距离、范围小的台风减弱后,云系扩散,与冷空气、副热带高压、其他台风等相互作用,有利于急流和持续性强降水的形成;低层水汽收入增加(减少)对于宁波降雨增强(减弱)的开始时间有6—12h提前;非地转湿Q矢量散度负值的增强(减弱)对于宁波强降雨的开始(减弱)有提前6h的预示意义。

Based on the data from the conventional and intensive observations,satellite,radar,and the NCEP(National Centers for Environmental Prediction)re-analysis,the typhoons affected Ningbo,which landed in Fujian province but not in Zhejiang province,were investigated.The possible causes of heavy rainfall-induced by Typhoon Fitow,Dujuan,and Meranti in Ningbo were discussed.The results indicate that 43.9%of eighty-two typhoons selected from 1949 to 2016 results in local rainstorms in Ningbo,9.8%results in local large rainstorms,and 4.9%causes a city-wide large rainstorm.75%of these typhoons occur after 2013.It is found that after the weakening of a small scale typhoon coming from far-distance,the interactions of cloud diffusion with cold air,subtropical high and other typhoons facilitate to the formation of jet current and continuous heavy rain in Ningbo.However,the extension and degree of its influence are difficult to grasp.The increase or decrease of low-level water vapor supply is 6-12 hours ahead of the beginning time of rainfall increasing or decreasing.The strengthening or weakening of negative non-geostrophic wet Q-vector divergence may indicate the beginning or weakening of heavy rain with 6 hours in advance.