Impact of the Preceding Boreal Winter Southern Annular Mode on the Summertime Somali Jet  

作　　者：SHI Wen-Jing XIAO Zi-Niu 

机构地区：[1]Department of Atmospheric Science,Nanjing University of Information Science & Technology [2]China Metrological Administration Training Center [3]Institute of Atmosphere Physics,Chinese Academy of Sciences

出　　处：《Atmospheric and Oceanic Science Letters》2014年第6期534-539,共6页大气和海洋科学快报（英文版）

基　　金：supported by the National Natural Science Foundation of China (41175051 and 41101045);Plans to Graduate Research and Innovation Projects of Jiangsu Province Colleges and Universities (CXZZ13_0517)

摘　　要：One of the major high-latitude circulation systems in the Southern Hemisphere is the Southern Annular Mode(SAM). Its effect on the Somali Jet(SMJ), which connects the Southern and Northern hemispheres, cannot be ignored. The present reported results show that time series of both the Southern Annular Mode Index(SAMI) during the preceding winter and the summertime Somali Jet intensity Index(SMJI) display a significant increasing trend and have similar interdecadal variation. The latter was rather strong around 1960, then became weaker up to the mid-1980 s, before starting to strengthen again. The lead-lag correlations of monthly mean SAMI with the following summertime SMJI showed significant positive correlations in November, December, and January. There are thus connections across two seasons between the SAM and the SMJ. The influence of the winter SAM on the summer SMJ was explored via analyses of SST anomalies in the Southern Indian Ocean. During strong(weak) SAM/SMJ years, the SST east of Madagascar is colder(warmer) while the SST west of Australia is warmer(colder), corresponding to the positive(negative) Southern Indian Ocean Dipole-like(SIODL) event. Subsequently, the SIODL excites an anticyclone located over the Arabian Sea in summer through air-sea coupling from winter to summer, which causes an increase in the summer SMJ intensity. The anticyclone/high branch of the SAM over the Southern Hemisphere subtropics and the cyclone/low over the east coast of Madagascar play an important role in the formation of Southern Indian Ocean "bridge" from winter to summer.One of the major high-latitude circulation systems in the Southern Hemisphere is the Southern Annular Mode（SAM）. Its effect on the Somali Jet（SMJ）, which connects the Southern and Northern hemispheres, cannot be ignored. The present reported results show that time series of both the Southern Annular Mode Index（SAMI） during the preceding winter and the summertime Somali Jet intensity Index（SMJI） display a significant increasing trend and have similar interdecadal variation. The latter was rather strong around 1960, then became weaker up to the mid-1980 s, before starting to strengthen again. The lead-lag correlations of monthly mean SAMI with the following summertime SMJI showed significant positive correlations in November, December, and January. There are thus connections across two seasons between the SAM and the SMJ. The influence of the winter SAM on the summer SMJ was explored via analyses of SST anomalies in the Southern Indian Ocean. During strong（weak） SAM/SMJ years, the SST east of Madagascar is colder（warmer） while the SST west of Australia is warmer（colder）, corresponding to the positive（negative） Southern Indian Ocean Dipole-like（SIODL） event. Subsequently, the SIODL excites an anticyclone located over the Arabian Sea in summer through air-sea coupling from winter to summer, which causes an increase in the summer SMJ intensity. The anticyclone/high branch of the SAM over the Southern Hemisphere subtropics and the cyclone/low over the east coast of Madagascar play an important role in the formation of Southern Indian Ocean ＂bridge＂ from winter to summer.

关 键 词：Southern Annular Mode Somali Jet Southern Indian Ocean Dipole ocean-atmosphere coupled bridge 

分 类 号：P434[天文地球—大气科学及气象学] P9