北半球夏季大气季节内振荡对中国东南沿海热带气旋暴雨的影响

摘要

本文采用美国台风联合警报中心整编的1981-2012年的best-track热带气旋资料、中国大陆743站逐日降水数据、亚太经合组织气候中心的北半球夏季季节内振荡(BSISO)指数和美国国家环境预报中心及大气研究中心的再分析资料,分析了中国东南部地区热带气旋暴雨特征及其与BSISO 8个位相的联系.结果表明:7、8月,中国东南沿海地区的热带气旋暴雨发生的频次最多,多个站点热带气旋暴雨占总暴雨频次的比例达40％以上.7、8月热带气旋暴雨主要发生于BSISO1的第1、2、7、8位相,发生的暴雨频次占总频次的78.4％,主要分布于福建省沿海地区和西南部;BSISO2的第5、6、7位相热带气旋暴雨发生的频次也较多,占总频次的73.6％,主要分布于福建省沿海地区及西南部和广东省西南沿海地区.对发生较多热带气旋暴雨的BSISO1和BSISO2位相背景下的环流合成异常的诊断显示,西北太平洋伸向中国东南沿海地区,大尺度引导气流为显著的异常东风带,有利于热带气旋登陆中国大陆;显著异常的纬向东风切变、气旋性相对涡度和整层水汽的异常辐合,有利于热带气旋登陆过程强度的维持,促使热带气旋暴雨发生在中国大陆.%The relationship between eight phases of boreal summer intraseasonal oscillation and tropical cyclone heavy rain in southeastern coast China was analyzed based on the Tropical Cyclone (TC)best-track data from the Joint Typhoon Warning Center,the daily precipitation data from 743 stations of China,the NCEP/NCAR reanalysis data from 1981 to 2012 and the BSISO indices from Apec climate cente.The result shows that the TC heavy rain in July and August occurred most frequently in the southeastern coastal areas of China,and TC heavy rain frequency proportion of monsoon heavy rain in many stations is over 40％.The TC heavy rain in July and August occurred mainly in phase 1,2,7,8 of BSISO1,which accounts for 78.4％,and is mainly distributed in the southeastern coast of Fujian Province and southwestern Fujian Province.It also occurred mainly in phase 5,6,7 of BSISO2,which accounts for 73.6％ and is mainly distributed in the southeastern coast of Fujian Province,southwestern Fujian Province and southwestern coast of Guangdong Province.Diagnosis of abnormal circulation in abnormal background of BSISO1 and BSISO2 in TC heavy rain in the phases that TC heavy rain happened mostly of BSISO1 and BSISO2 shows there is a significant anomalous easterlies of the large-scale steering current in the Northwest Pacific extending to the southeastern coastal areas of China that makes it easy for the TC to land China.Abnormal easterly shear of vertical zonal wind,abnormal cyclonic relative vorticity and abnormal column-integrated moisture convergence are helpful to maintain the landfall TC,so that the TC heavy rain occurs in the southeastern coastal areas of China.