2017年秋季华西秋雨的多时间尺度变化特征及成因分析  

Characteristics of Variability on Multiple Timescales and Cause Analysis of Autumn Rainfall in West China During 2017

作　　者：梁萍 周兵[3] 马悦[1] 汪佳伟[1] LIANG Ping;ZHOU Bing;MA Yue;WANG Jiawei(Shanghai Climate Centre,Shanghai 200030;Key Laboratory of Cites'Mitigation and Adaptation to Climate Change in Shanghai,CMA,Shanghai 200030;National Climate Centre,Beijing 100081)

机构地区：[1]上海市气候中心,上海200030 [2]中国气象局上海城市气候变化应对重点开放实验室,上海200030 [3]国家气候中心,北京100081

出　　处：《气象》2019年第8期1104-1112,共9页Meteorological Monthly

基　　金：国家重点研发计划(2017YFC1502301);国家自然科学基金项目(41775047);国家重点基础研究发展计划(973计划)(2012CB955901);上海市气象局青年起航计划;国家气象科技创新工程“次季节至季节气候预测和气候系统模式”共同资助

摘　　要：利用我国723个常规观测气象站降水资料和NCEP再分析资料等,综合大气环流的季节内-季节异常、海洋外强迫年际异常及降水的长期变化影响,分析了2017年华西秋雨异常的成因。结果表明:20世纪60年代以来,华西秋雨存在3~4、6~9、12~18 a、36 a等多个时间尺度的准周期变化,并自1990年以来呈现增加的长期变化趋势。2017年华西秋雨异常偏多是多时间尺度变率叠加影响的结果。2017年秋季,北半球极涡偏向东亚地区,贝加尔湖低槽多冷空气分裂南下,西太平洋副热带高压异常偏强偏西,华西地区处于水汽输送异常辐合大值区,出现降水异常偏多。在季节内时间尺度上,东亚夏季风的季节内撤退过程偏慢,夏季风北界位置持续偏北,9-10月主雨带维持在华西—江汉—江淮一带。自西太平洋经南海北上的水汽输送的季节内变化,并与东北冷涡的季节内活动相配合,是造成华西秋汛的季节内环流影响因子。华西秋雨年际异常与赤道中东太平洋海温呈现显著的负相关。夏末秋初开始发展的拉尼娜状态是2017年我国秋季降水异常的重要外强迫因子。2017年华西秋雨的异常偏多也与其近年来的年代一多年代际正距平位相及长期增加趋势相关联。Based on the precipitation observations from 723 basic meteorological stations in China and the NCEP reanalysis data,the possible causes of the 2017 autumn rainfall anomalies in West China were investigated by detailed investigations about the impacts of sub-seasonal to seasonal anomaly of atmospheric circulation,interannual anomaly of external forcing from ocean together with long-term variations of precipitation.The results show that quasi-period variations with multiple timescales,including 3—4 a,6—9 a,12—18 a and 36 a since 1960 s,along with an increasing long-term trend since 1990 found in the autumn rainfall in Western China.The abnormal heavy rainfall in West China during autumn of 2017 resulted from the superposition influences from multi-time scale variations.In the autumn of 2017,the position of polar vortex in the Northern Hemisphere lay towards East Asia,allowing the cold air from the low trough near Lake Baikal to splitting southward.Meanwhile,the West Pacific subtropical high was excessively stronger and westward.Therefore,a stronger water vapor convergence area was formed and eventually led to the abnormal heavy rainfall in West China.On sub-seasonal time scales,the East Asian summer monsoon retreated more slowly than normal,and the northern boundary position of the summer monsoon was continuously maintained northward than normal.The main rain band was correspondingly maintained around the region of West China,Jianghuai and Hanjiang in September and October.The sub-seasonal variations of the northward water vapor transportation from the West Pacific Ocean through the South China Sea,together with the sub-seasonal activities of northeastern cold vortex,may be sub-seasonal circulation factors which influence the autumn rainfall anomaly in West China.In addition,the interannual anomaly of autumn rainfall in West China and central-eastern equatorial Pacific SST shows a remarkable negative correlation.The La Nina condition which developed from the late summer and early autumn in 2017 acts as the i

关 键 词：华西秋雨 夏季风 拉尼娜 西太平洋副热带高压 多时间尺度 

分 类 号：P466[天文地球—大气科学及气象学]