夏季热带东风急流的结构、变化及其与亚非季风降水的关系  

The Structure and Variation of Tropical Easterly Jet and its Relationship with the Monsoon Rainfall in Asia and Africa

作　　者：陈桦[1] 丁一汇[2] 何金海[3] 

机构地区：[1]江苏省常州市气象局,常州213001 [2]国家气候中心,北京100081 [3]南京信息工程大学大气科学学院,南京210044

出　　处：《大气科学》2007年第5期926-936,共11页Chinese Journal of Atmospheric Sciences

基　　金："九五"国家攀登A项目"南海季风试验研究(SCSMEX)";KLME060201;国家重点基础研究发展规划项目2006CB403607

摘　　要：使用NCEP/NCAR再分析资料研究热带东风急流(TEJ)的长期变化及其与亚非降水分布的关系。用150~100 hPa纬向风代表TEJ,并定义了一个指数(TEJI)来度量急流的变率。分析发现,TEJ主要覆盖了热带地区从日界线向西延伸到非洲西海岸的大片地区,其核心位于150~100 hPa印度半岛南部10°N^15°N,中心风速超过30 m/s。急流中线大致位于70°E,以东是急流的入口区,以西是出口区。在入口区急流轴线有两个分支,南支位于0°~10°N,呈西北-东南走向,北支位于10°N^20°N,呈西南-东北走向。TEJ存在40~60天和20~30天的季节内振荡周期,以及2~4年和7~10年的周期变化。出现暖事件时TEJ减弱,出现冷事件时TEJ加强。TEJ存在明显的年代际变化,1978年是其气候突变点,突变前为强TEJ时期,突变后TEJ显著减弱。亚洲和中非的主要降水带、对流区、高层辐散及大尺度上升运动都出现在东风急流入口区的右侧及出口区的左侧,但出口区西非的情况略显复杂。在急流的入口区和出口区存在两个近于相反的垂直环流,它们与降水分布密切有关。在急流的入口区,强TEJ年其垂直环流更强,其右侧的降水也更大;但在急流的出口区,强、弱TEJ年的垂直环流没有明显差异,其左侧的降水也没有明显差异。The long-term variation of the Tropical Easterly Jet （TEJ） and its relationship with the distribution of rainfall in Asian and African monsoon regions are studied using the National Center for Environmental Prediction/ National Center for Atmospheric Research （NCEP/NCAR） reanalysis data from 1958 to 2002. TEJ is denoted by 150-100 hPa zonal wind, and an index （TEJI） is defined to measure the variability of TEJ. It is shown that TEJ covers large tropical areas extending from the date line to the west coastal regions in Africa. Its core is located in 10° N-15°N in southern Indian peninsula with the maximal speed larger than 30 m/s, and the mid-line lies around 70°E, its east being the entrance region and its west the exit region. There are two branches of the TEJ axis in the entrance region, the southern one in 0°- 10°N lying northwest-southeast and the northern one in 10°N- 20°N lying northeast-southwest. Westerly prevails in the mid-latitudes, while easterly is limited in the lower-latitude areas with its maximal intensity in the layer of 150 - 100 hPa. The zonal wind shear between the upper and lower troposphere is very significant in the Asian-African monsoon regions, but easterly occupies almost the entire troposphere in the tropical oceans. TEJ has intraseasonal oscillation （ISO） with periods of both 40 - 60 days and 20 - 30 days, but the latter is not significant. The disturbance starts to travel eastward and westward from the dateline along 7.5°N- 12.5°N, and it starts to travel northward from the equator along 70°E. TEJ has interannual variation with periods of 2 - 4 years and 7 - 10 years. Generally it is negatively correlated with ENSO.. TEJ weakens in warm events and strengthens in cold events. Compared to La Nifia years, easterly is weaker in E1 Nifio years. TEJ has obvious interdecadal variation, and 1978 is its climate jump year. It is a strong TEJ period before 1978, and TEJ weakens significantly after the climate jump. In Asia and central Africa, the primary rainfall

关 键 词：热带东风急流 季风降水 垂直环流 

分 类 号：P425[天文地球—大气科学及气象学]