夏季东亚副热带西风急流不同尺度波的特征分析

ANALYSIS OF THE CHARACTERISTICS OF THE EAST ASIAN SUBTROPICAL WESTERLY JET UNDER DIFFERENT SCALES IN SUMMER

利用1960—2015年NCEP全球再分析日平均资料和中国国家气象站20时的日降水量资料,分析在超长波、长波和天气尺度波的不同尺度纬向风场中,夏季东亚副热带西风急流的空间分布和活动特征,初步研究了不同尺度波的东亚副热带西风急流与典型梅雨异常年降水的关系,通过分析东亚副热带急流的周期性变化,进一步探讨本研究工作的实际应用价值。研究表明,超长波是东亚副热带西风急流扰动的主要成分,与急流位置的演变具有较高的一致性,对于梅雨期间的雨带位置和强度变化均有较好的指示意义;长波、天气尺度波是叠加在超长波上的次低频和中间尺度扰动,后者与梅雨强度的变化有一定对应关系。东亚副热带西风急流与其超长波的位置变化具有明显的单、双周振荡特征,在实际预报业务中可以充分利用超长波的周期性和较高预报技巧,为中期天气分析和预报提供更有价值的参考信息。

By using the daily reanalysis data provided by National Centers for Environmental Prediction- National Center for Atmospheric Research （NCEP-NCAR） and daily precipitation data at 20：00 BT （Beijing Time） from Chinese meteorological stations during 1960-2015, spatial distribution and activity characteristics of the East Asia subtropical westerly jet （EASWJ） in summer, which are in zonal wind wave with the ultralongwave, long wave and synoptic-scale wave, are analyzed. A preliminary study on the relationship between the EASWJ with different spatial scales and typical Meiyu precipitation is performed. Research shows that ultra long wave is the main component of the disturbance of EASWJ, highly consistent with the position evolution of the jet stream.It also has a nice indication for rain belt change in position during the period of Meiyu. In addition, long wave and synoptic scale waves are sub-low frequency and medium-scale perturbations superimposed on ultra long waves, which has a certain corresponding relationship with the change of Meiyu intensity. The position change of the EASWJ and ultra long wave has a obvious characteristics of weekly and biweekly oscillation. So,full use of ultra long wave cycle may provide valuable reference information for medium-term weather analysis and forecasting.