江南南部初夏雨季的降水和环流气候特征  

Climatic Characteristics of Rainfall and Atmospheric Circulation during the Early Summer Rainy Season in the South Part of Jiangnan

作　　者：苗长明[1,2] 郭品文[1] 丁一汇[3] 刘樱[4] 沈杭锋[2] 

机构地区：[1]南京信息工程大学,南京210044 [2]杭州市气象局,杭州310051 [3]国家气候中心,北京100081 [4]浙江省气候中心,杭州310002

出　　处：《大气科学》2014年第2期285-296,共12页Chinese Journal of Atmospheric Sciences

基　　金：浙江省社会发展项目2009C33053

摘　　要：基于1961~2010年气象台站逐日降水资料、同期美国NCEP/NCAR的逐日再分析格点资料,通过气候平均、REOF分析、聚类分析等方法,分析了江南地区初夏降水的地域性和时段性特征,及西太平洋副高和高、低空急流等大气环流的相应演变过程。结果发现:(1)江南南部27.5°~29.5°N存在一个独立于华南前汛期和江淮梅雨的初夏雨季,该雨季平均发生时间为6月11~30日,比江淮梅雨早约8天左右。(2)西太平洋副高的西伸东退是江南南部初夏雨季发生发展的重要环流背景,6月第2候副高发生突变性加速西伸之后雨季开始,雨季期间850hPa副高西伸脊点基本稳定在最西位置即133°E附近,6月第6候副高东退北抬后雨季结束。(3)低层急流大风带的形成和位置是江南南部初夏雨季阶段的重要动力条件,印度洋和孟加拉湾向东北延伸的低层急流与西太平洋副高西北侧的气流连通形成低层急流大风带,并与北侧上空的高空急流耦合,降水集中区位于低层急流大风带左侧、高空急流入口区右侧。Daily surface observation precipitation datasets from 1961 to 2010 and National Centers for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） reanalysis datasets were used to perform rotated empirical orthogonal function （REOF） and cluster analyses in determining the climatic characteristics of the early summer rainfall and relevant atmospheric circulation in the southern part of Jiangnan, which is the southern region of the Yangtze River. The results reveal a concentrated rainy period in the region, which is the early summer rainy season independent of the pre-flood season in South China and the Meiyu in the Yangtze-Huaihe River basin. This rainy season has an average duration of 20 days and generally begins on June 11, approximately 8 days before the start of the Meiyu. In addition,movement westward and eastward of the West Pacific subtropical high （WPSH） provide important circulation backgrounds for this rainy season. That occurring after the WPSH extended westward abruptly and rapidly in the pentad of June 5-10. The west ridge points of the WPSH at 850 hPa remained steady near 133~E, which is its westernmost point during the rainy season, then the early summer rainy season ended as the WPSH retreated eastward and shifted northward at the end of June. Moreover, low-level jet （LLJ） patterns are significant dynamic factors during the early summer rainy season. The LLJ at 850 hPa from the Bay of Bengal and Indian Ocean connected with the wind current at the northwest side of the WPSH and coupled with the upper-level westerly jet at the region of concentrated precipitation located to the left of the LLJ and to the ri~,ht of the unner-level let inflow boundarv oreciselv in the southern oart of Jian^nan.

关 键 词：江南南部 初夏 雨季 大气环流 

分 类 号：P462[天文地球—大气科学及气象学]