梅雨期高层流场对低层急流及中尺度系统影响的数值试验

A NUMERICAL STUDY ON THE INFLUENCE OF WIND FIELDS AT UPPER LEVELS IN THE MEI YU PERIOD ON THE DEVELOPMENT OF LOW LEVEL JET AND MESOSCALE SYSTEMS

中文关键词:  梅雨锋暴雨  高低层流场耦合  数值试验

英文关键词:Heavy rainfall on mei-yu front  Coupling of high and low level winds  Numerical ex periments

中文摘要:

      用中尺度模式对一次江淮流域暴雨过程进行了数值试验,并研究了对流层高层青藏高压东侧偏北大风的强弱与低层流场及中尺度系统发生及至降水过程的影响。试验不仅较成功地模拟了本次暴雨过程及相应的系统,而且揭示出较强的高空偏北大风将引起对低空急流的加强。而更为重要的是低层切变线的出现以及其上中尺度涡旋的发生。上下风场所构成的垂直反环流圈大大有利于对流的发展,特别是在切变线地区的上升支,带有明显的中尺度特征。

英文摘要:

      Using a mesoscale model a numer ical study on a heavy rainfall case occurring in the Yang tze-Huaihe River Valley is made in this paper.The influence of the intensity of northeast erly wind in front of the Tibet an High at upper level on the low level wind field and development of mesoscale systems as well as heavy rainfall is invest igated.The model well repro duced the heavy rainf all process and the weather systems associated.And it indicates that the strong northeas terly flow around the High atupper troposphere will bring about notonly the streng thening of low level southeast erly wind,but also the appear ance of shear-line and mesoscale vortex at low level.The coupling of northerly wind at upper level and southerly wind at lower level constructs an indirect vertical circulation which is most favourable for the development of conv ective motions.Its ascending branch in the shear-line area is very strong and shows a pro nounced mesoscale characteristic.