上海夏季海风锋及其触发对流的时空分布和环流背景分析  

CHARACTERISTICS AND CIRCULATION BACKGROUND OF SHANGHAI SUMMER SEA BREEZE FRONT AND ITS INDUCED CONVECTION

作　　者：顾问[1,2,3] 张晶[2] 谈建国[1,3] 戴建华[2] 岳彩军[1,3] 

机构地区：[1]上海市气象科学研究所/上海市卫星气象遥感应用中心,上海200030 [2]上海中心气象台,上海200030 [3]上海市气象与健康重点实验室(上海市气象局),上海200030

出　　处：《热带气象学报》2017年第5期644-653,共10页Journal of Tropical Meteorology

基　　金：国家自然科学基金项目(41275021);气象关键技术集成与应用面上项目(CMAGJ2015M21);上海市科委项目(13231201400)共同资助

摘　　要：基于2011—2014年6—9月多普勒雷达、加密自动站和NCEP/NCAR再分析资料,对上海地区海风锋及其触发对流的时空分布和环流背景进行统计,得出主要结论:(1)近4 a来上海夏季海风锋登陆65次,其中海风锋触发对流19次。海风锋最早于09时登陆,平均持续时间为5.2 h。海风锋触发对流时段为13—15时,对流平均维持时间为2.5 h。海风锋触发对流多出现在市区、北部郊区和浦东新区,呈现强局地性;(2)根据海风锋登陆点将海风锋分成北支、南支和双支3种类型。海风锋类型与环境风向密切相关,环境风为东北风时形成南支海风锋,环境风为偏南风和西南风时形成北支海风锋,环境风为偏西风时形成双支海风锋。南支海风锋不易触发对流,这与其出现时上海的热力条件不如北支和双支海风锋出现时有关;(3)海风锋触发对流日的环流背景为:500 hPa副热带高压强盛,上海受副高控制;中低层西南风增温、增湿,促进层结不稳定;低层925 hPa为弱西风。海风锋触发对流日的大气可降水量和K指数显著大于无对流日,但与其它对流日无明显差异。Based on the Doppler radar, encrypted automatic stations and NCEP/NCAR reanalysis data from June to September, 2011--2014, the spatial and temporal distribution of a sea breeze front （SBF） and its induced convection were investigated. The results show that during the 4 years the summer SBF landed 65 times, while SBF-induced convection occurred 19 times. The SBF is prone to land at 0900 to 1200 （local time） withan average duration of 5.2 hours. SBF-induced convection tends to happen at 1300 to 1500 withan average duration of 2.5 hours. It has strong local characteristic, most likely to occur in the downtown areas, Pudong New District and Baoshan District. The SBF is divided into 3 categories according to its landing site： N-SBF landing from Yangtze River estuary, S-SBF landing from Hangzhou Bay and SN-SBF landing from both sides. Compared with SN and N-SBF, S-SBF is more difficult to trigger the convection because of the poor thermal conditions. Types of SBF depend largely on the direction of background wind. S-SBF occurs when background wind is northeasterly, N-SBF occurs when background wind is southerly and southwesterly, SN-SBF occurs when background wind is westerly.During the SBF-triggering convection days, Shanghai is under the control of a 500 hPa subtropical high. At 700 and 850 hPa southwesterly wind increases warm and humidity, promoting stratification instability. Westerly wind is rather weak at 925 hPa. PWV and K index are much greater at convection-induced days than convection-free days.

关 键 词：海风锋 对流 多普勒雷达 统计特征 时空分布 环流背景 

分 类 号：P458.121.1[天文地球—大气科学及气象学]