2015年汛期我国南方季节内东西反相旱涝型及环流特征

The West-East Reverse Pattern of Intraseasonal Rainfall and Corresponding Circulations in the 2015 Flood Season

本文利用站点数据、再分析数据,采用经验正交函数分解(EOF)、合成分析等统计方法,探讨了2015年汛期(4—9月)内我国南方逐候降水的空间模态及其对应的环流特征。结果表明:2015年汛期,南方地区汛期总体表现为东西反向降水型,体现了强El Nino发展年的一般特征,但进一步分析发现汛期内候尺度东西反向降水型具有多样性特征。对候尺度降水资料EOF展开后的第一模态(EOF1)和第三模态(EOF3)为两类东西反相型降水,在对流层高、中、低层都有明显的差异。EOF1东多西少(A1)型是由低层菲律宾反气旋主导的降水型,副热带高压偏强西伸显著,南亚高压偏强偏东,我国南方东部的大部分地区降水偏多。而EOF3的东多西少(A2)型是由热带气旋活动主导的降水型,南海北部为气旋式环流;副热带高压偏强,相对于A1型偏东;南亚高压较常年同期偏强、偏东,东南沿海降水偏多。EOF1的东少西多(B1)型明显受到南下冷空气活动的影响,副热带高压偏强,位置相对偏东,印缅槽增强,有利于南方西部降水偏多。而EOF3的东少西多(B2)型是菲律宾反气旋位置异常主导的结果,副热带高压明显偏强偏西,引导水汽到南方西部地区。2015年汛期内东西反相旱涝型与菲律宾反气旋活动及位置、热带气旋活动及位置、冷空气活动路径有密切的关系,受到多种环流配置的影响。

Based on the observation and reanalysis data, the spatial mode and corresponding circulation characteristics of precipitation anomaly under pentad scale in Southern China during the 2015 flood season （from April to September） are analyzed by using the methods of empirical orthogonal function （EOF）, composite analysis and significance test. The results show that the west-east reverse pattern of precipitati- on anomaly is the major mode in the developing phases of strong E1 Nifio years and the pentad pattern in 2015 shows similar features. But the pentad scaIe of precipitation anomaly patterns can be divided into two types of west-east reverse patterns by using the first and third EOF mode, and they have obvious differ- ences in upper, middle, lower levels of the troposphere. The precipitation anomaly pattern of more in east and less in west （A1） with the first EOF mode is dominated by the anticyclone activities around Philippines at the low level, but the pattern of more in east and less in west （A2） with the third EOF mode is domina- ted by tropical cyclone activities. The pattern of less in east and more in west （B1） with the first EOF mode is obviously affected by the moving southward of the cold air activities, but the pattern of less in east and more in west （B2） with the third EOF mode is dominated by abnormal position of the anticyclone ac- tivities around Philippines at the low level. The precipitation anomaly features of west-east reverse pattern in Southern China during the 2015 flood season are closely related to the positions of anticyclones around Philippines, tropical cyclone activities and the moving path of the cold air activities.