摘要
本文用13年夏半年(5—10月)月平均风场和两年逐日风场资料研究了200hPa南亚热带东风急流的气候学特征和中期振荡过程。研究表明,南亚夏季热带东风急流显著的非季节性变动和年际差异与低纬对流层高层大尺度环流变化和南亚夏季风活动密切相关,相对于多年平均而言,存在5类异常的东风急流。 各种分析表明,热带东风带存在三种主要的中期振荡。准50天周期振荡与夏季南亚对流层上部大尺度散度场的变化相关联,表现为十分显著的向南的位相传播。准50天和25天振荡均存在显著的年际变化。准50天周期振荡系统性不强的年份,准25天周期振荡是低纬行星波的主要振荡,在东风急流区除表现为系统性向西传播外也表现为向南的位相传播。准双周振荡在东风带一般向西传播。
Based on 13 year monthly mean wind and 2 year day -to-day wind for Northern summer (May to September), a study on the climatological features and medium -range oscillations of South Asia tropical easterlies at 200 hpa was made. The significant intraseasonal and interannual changes in the TEJ characterized by 5 kinds of anomalous patterns, and its close relationship to low latitude upper -tropospheric, broad -scale circulation anomaly and to South Asia summer monsoon, were discussed .
Three kinds of medium-range oscillation in the easterlies were found. The quasi -50 day oscillation related to the summer upper-tropospheric, broad-scale divergent changes over South A-sia possesses southward phase propagation over summer monsoon region. It was also found that the quasi - 50 and 25 day oscillations assume prominant interannual change. In the year with weak quasi -50 day oscillation, the dominant oscillation of low latitute planetary wave, which shows equatorward phase propagation and systematic westward propagation, is the quasi - 25 day oscillation. The biweekly oscillation, in general, propagates westward in the easterlies.
出处
《热带气象》
CSCD
1990年第1期12-22,共11页
