中东急流的季节变化特征及其与热力影响的关系

Seasonal variation features of Middle East jet stream and its relation with thermal effect

采用多年平均的NCEP/NCAR再分析资料,研究了中东急流强度和位置的季节变化特征及其与南北温差的关系。结果表明:1)中东地区上空西风带的强度和位置的垂直结构均具有明显的季节变化特征,冬、春季西风中心强度较大,夏、秋季西风中心强度较小;600hPa以上,冬、春季西风中心位置偏南,夏、秋季西风中心位置偏北。各季节的所有高度上,200hPa的西风中心风速最大。2)中东急流的强度和位置具有明显的季节变化特征。冬半年(11月—次年4月)中东急流较强,南北位置基本维持在27.5°N附近;夏半年(5—10月)中东急流较弱,5月后急流中心位置偏北,6—9月位于40°N附近,10月南撤至32.5°N。3)中东急流的强度和南北位置变化与500～200hPa整层平均的南北温差的对应关系很好,根据热成风原理,认为南北温差的季节性变化对中东急流的强度和南北位置变化具有重要影响。

Based on the annual average NCEP/NCAR reanalysis data,the seasonal variation characteristics of the intensity and location of the Middle East jet stream（MEJS）and their relations with the South-North temperature differences（SNTD）are discovered.Results show that there are obvious seasonal variation characteristics for the vertical structures of intensity and location of westerlies over the Middle East area.The intensity of westerly center is stronger in winter and spring,but weaker in summer and autumn.Above 600 hPa,the location of westerly center is southward in winter and spring,but northward in summer and autumn.In each season,the velocity of 200 hPa westerly center is maximum.The intensity and location of MEJS have obvious seasonal variation characteristics.MEJS is stronger and locates in 27.5°N from November to the next April.MEJS is weaker from May to October and moves northward after May with its center maintaining over about 40°N from June to September and 32.5°N in October.The seasonal variation characteristics of the intensity and location of MEJS are significant with good corresponding relations to the SNTD averaged from 500 to 200 hPa.It shows that the seasonal adjustment of SNTD has important effects on the seasonal variations of intensity and location of MEJS according to the principle of thermal wind.