1998年夏季热带内外大气低频振荡特征分析

THE FEATURES OF THE TROPICAL AND EXTRA-TROPICAL ATMOSPHERIC LOW FREQUENCY OSCILLATION DURING THE SUMMER OF 1998

利用ECMWF的格点风和位势高度场资料,对1998年夏季热带内外地区大气低频振荡特征进行了分析研究。结果表明,亚洲季风区的季节内振荡非常显著。850hPa季节内振荡纬向风的经向传播揭示出南海地区的西风振荡受南北两支西风的共同影响。与长江流域特大洪涝密切相关的大气环流系统(乌拉尔阻高和西太平洋副高)对季节内振荡有较强的响应。在欧亚范围,持续性异常环流十分活跃,大气低频波的活动与环流持续异常的形成有密切的联系,季节内振荡是高低纬环流持续异常同时发生的纽带。其低频(30～60d)遥相关型的分布同江淮洪涝年的波列结构相类似。

The characteristics of the tropical and extra-tropical atmospheric low frequency oscillation during the summer of 1998 is studied based on the ECMWF grid wind and height data. Results show that intraseasonal oscillation over Asian monsoon regime is obvious. Latitudinal propagation of zonal wind at 850 hPa intraseasonal oscillation show that oscillation of westerlies over the South China Sea region is affected by two separated branches of northern and southern westely belts. Atmospheric circulation systems (Ural blocking high pressure and western Pacific subtropical high pressure) which are closely associated with severe flood around Changjiang River basin strongly response to intraseasonal oscillation. Persistent anomalies are active over the Eurasian continent. Activities of atmospheric low frequency wave are closely associated with the forming of circulation perisistent anomalies. Intraseasonal oscillation is the key to simultaneous occurrence of persistent anomalies at high and low latitudes. Distribution of low frequency (30～60 d) teleconnection pattern is an analogue to the wave train structure of Changjiang and Huaihe River flooding year are analogue.