浙江秋季连阴雨气候统计特征及其异常环流背景  

Statistical characteristics of persistent autumn rainfall in Zhejiang Province and the associated circulation anomalies

作　　者：陈懿妮 楼茂园 李嘉鹏 娄小芬 刘汉华 CHEN Yini;LOU Maoyuan;LI Jiapeng;LOU Xiaofen;LIU Hanhua(Zhejiang Meteorological Observatory, Hangzhou 310017, China)

机构地区：[1]浙江省气象台

出　　处：《气象科学》2019年第2期264-273,共10页Journal of the Meteorological Sciences

基　　金：国家自然科学基金资助项目(41605035);浙江省气象局预报员专项(2016YBY24)

摘　　要：利用1971—2016年浙江常规气象站观测资料和多种再分析资料,分析了浙江省秋季连阴雨的气候特征及其异常环流背景。结果表明:(1)浙江每年每站平均出现1.8次秋季连阴雨天气,过程平均可持续5.5 d,平均雨量77 mm;秋季3个月中9月出现连阴雨的频次最高;大多年份会发生1~2次持续5~7 d的连阴雨,78%过程累计降水量在100 mm以下;发生时多为全省一致变化型,多发区集中在杭州—绍兴一带。(2)连阴雨过程次数、累计持续天数及累计降水量有一致变化性,均反映出浙江秋季连阴雨有明显的年际变化特征,有4个强年和7个弱年。(3)浙江秋季连阴雨强(弱)年对应南亚高压和西太平洋副热带高压“相向(背)而行”。强(弱)年时,西太平洋副热带高压异常偏西(东),南亚高压异常偏东(西),华东地区上空垂直上升运动强(盛行下沉气流),低层异常偏南(北)风提供了充足的水汽(阻碍了暖湿空气北上),有(不)利于浙江连阴雨的发生。(4)连阴雨强弱年大气环流异常与热带海表温度强迫有关。强(弱)年时,赤道太平洋海温呈拉尼娜状态(距平不明显),使东印度洋—南海—海洋性大陆上空对流活跃(偏弱),潜热加热(不足以)激发低层Matsuno-Gill型响应,(不能)在亚洲大陆激发气旋性环流异常,而赤道中东太平洋强(弱)下沉气流则(不能)在西北太平洋激发反气旋性环流异常,此低层气旋—反气旋异常环流配置(弱环流异常)使华东地区有低层偏南(北)风异常,水汽增多(减少),有(不)利于浙江连阴雨的发生。Based on the conventional observational data and reanalysis data of Zhejiang Meteorological Station from 1971 to 2016, the statistical characteristics of persistent rainfall in autumn in Zhejiang Province were analyzed. The results are shown as follows.(1) The average rainfall frequency in Zhejiang is 1.8 times per year, with each time lasting 5.5 days, and the average rainfall is 77 mm. In the three month of autumn, it is the most possible to see the continuous rainy weather in September. There is 1-2 times continuous rainy weather lasting 5-7 days in most years, and 78% of such weather has the cumulative precipitation below 100 mm. These characteristics are universal for the whole province, and the prone area is located in Hangzhou-Shaoxing region.(2) There are consistent characteristics in the frequency, accumulative lasting days and accumulative rainfall, which all characterize obvious interannual variation. There are 4 strong years and 7 weak years.(3) The strong (weak) year occurs when the South Asian high and the western Pacific subtropical high meet each other halfway (go back on each other). In strong (weak) years, the western Pacific subtropical high locates in the west (east) anomalously, and the South Asian high locates in the east (west) anomalously;the uplift (sinking) airflow prevails over the East China region, and the low-level anomalous south (north) wind brings (hinders) the warm and wet air, which are (not) conducive to the occurrence of persistent rainy weather.(4) The atmospheric circulation anomaly in strong and weak years is related to the tropical sea surface temperature forcing. In strong (weak) years, the equatorial Pacific sea temperature is in the La Ni a state (with unapparent anomaly), which makes the convection over the eastern Indian Ocean-South China Sea-Oceanic Continent more active (weaker). The latent heating stimulates (is not strong enough to stimulate) the low-level Matsuno-Gill response, and the cyclone circulation anomaly on the Asian continent is (cannot be) excited, so

关 键 词：秋季连阴雨 时空变化 强弱年 大气环流异常 热带海温强迫 

分 类 号：P434[天文地球—大气科学及气象学]