华南前汛期降水年代际异常特征及成因
投稿时间: 2016-02-24  最后修改时间: 2016-03-07  点此下载全文
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李丽平 南京信息工程大学 li.liping@163.com 
中文摘要:摘要:利用1981—2013年160站逐月降水资料、NCEP/NCAR逐月再分析资料、NOAA海表温度资料等,研究了华南前汛期降水年代际异常时空特征及其可能成因。结果表明:(1)华南前汛期降水在1992左右发生由异常偏少转为偏多的显著年代际转折,最显著异常中心位于广西东北部和广东北部。(2)1990s’初发生的对流层高层南冷北暖(40°N附近为界)、对流层下暖上冷的年代际转折,使得高低层环流场均出现了有利于北方干、湿冷空气和孟加拉湾、西太平洋暖湿水汽在华南区域交汇并辐合上升的形势,造成华南前汛期降水发生偏少转偏多的显著年代际转折。年代际转折前后两个时段中,位于热带的孟加拉湾槽、东亚沿岸EAP遥相关型波列中的西太平洋副高、阿拉斯加湾附近的脊,以及中纬度贝加湖以西以南脊的强度或位置均具有显著差异,故这些环流系统的年代际异常是华南前汛期降水年代际异常的重要原因。(3)南太平洋关键区海温在1990s’初开始呈现增暖趋势,在偏暖(冷)时期,华南低空受异常气旋(反气旋)环流控制,对流层上层西风急流偏弱偏南(偏强偏北),造成华南地区降水异常偏多(偏少)。
中文关键词:华南前汛期  降水  年代际异常  东亚大气环流  南太平洋海温
 
Interdecadal anomaly of rainfall during the first rainy season in
Abstract:Abstract: Based on the monthly mean rainfall data at 160 China stations, NCEP/NCAR reanalysis dataset, and NOAA sea surface dataset for 1981-2013, the temporal and spatial distributions of the interdecadal anomaly of precipitation and its possible causes over South China during the first rainy season are investigated. The results show that: (1) the precipitation over South China in around 1992 occurred an significant interdecadal turn from negative to positive anomaly, the center of the most evident anomaly located in northeast Guangxi and north Guangzhou. (2) The significant interdecadal changes in 1990s’ when the south was colder than north in the upper troposphere (40癗 bounded) and the lower was warmer than the upper in the troposphere, made high-low level circulation field presenting a favorable situation, which is in favor of the cold air in the north meeting with the warm and wet water vapor from Bay of Bengal and west Pacific and making a convergence and rising in South China; the meridional circulation at mid-latitude of 500hPa geopotential height enhanced, the Bay of Bengal trough deepened in tropics, East Asia-Pacific pattern (EAP) appeared “ - ” anomaly from south to north, and the western Pacific subtropical high is strong and southerly position; the 850hPa wind field had an abnormal anticyclone (cyclone) circulation in the east to Philippines ocean (Hetao of China to Japan Sea), South China was controlled by a cyclone circulation; subtropical westerly jet at the upper troposphere was weak and southerly, these all resulted a significant interdecadal turn of precipitation over South China. During the two periods before and after the interdecadal turning, there are significant differences for the strength and position of the Bay of Bengal trough over the tropical, the west Pacific subtropical high and the ridge near the Gulf of Alaska in EAP teleconnection wave train, and the ridge to the south and the west of Lake Baikal over the mid latitude, so the interdecadal anomalies of these systems are the important reasons of the precipitation anomalies during the first rainy season in South China. (3) The interdecadal anomaly over the key region of south Pacific sea surface temperature had a great effect on the first rainy East Asia general atmospheric circulation and precipitation in South China. South Pacific temperature occurred remarkable warming trend in the early 1990s’. During the warm (cold) period, the low level of South China was controlled by anomaly cyclone (anticyclone) circulation, upper-tropospheric westerly jet was weak and southerly (strong and northerly), which made the abundant(lack) of precipitation.
keywords:First rainy season of South China  Precipitation  Interdecadal anomaly  General atmospheric circulation in East Asia  South Pacific temperature
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