东亚大尺度低空急流的背景流场与东半球的越赤道气流

本文介绍了关于东亚大尺度低空急流背景流场的研究,指出其上游的季风西风带对它的重要作用,以及它与东非地区越赤道气流之间的关系。利用欧洲中期预报中心提供的资料,考查了1979,1982和1983年8个夏季月的东亚大尺度低空急流,进一步研究了它们的上游流场和背景气流,指出东亚地区的低空急流主要以亚洲季风为背景。大风动量一次一次地沿着季风气流向急流区传播,它还与越赤道气流关系密切;绝大多数大尺度低空急流是东半球几支越赤道气流东传后汇合的产物。5月,以80°E附近的越赤道气流为主;6月中旬后,索马里地区低空急流建立,东非越赤道气流成为主要的影响系统,并经常与105°E的越赤道气流共同作用影响我国或东亚地区的低空急流。

THE RELATIONSHIP BETWEEN LARGE SCALE LOW LEVEL JET OVER EAST ASIA AND MONSOON AS WELL AS CROSS-EQUATORIAL CURRENTS IN SUMMER

A review regarding the investigation of the background circulation of large scale low-level jet over East Asia is given, which indicates the important effect of the monsoon westerlies on LLJ and the relationship between LLJ and cross-equatorial currents.The data of the Global Analyses provided by ECMWF are used to investigate the relationship between LLJ and monsoon as well as cross-equatorial currents. It indicates that a large amount of momentum of the monsoon westerlies is transferred downstream to the low-level jet area, strengthening the jet speed. Most of the LLJ over Asia are connected with the cross-equatorial currents in Eastern Hemisphere. The cross-equatorial currents near 80°E are the main currents connected with LLJ in May. However, once the Somaria jet is. established, it becomes the main flow together with the cross-equatorial currents. near 105°E to influence the low-level jet over East Asia.