初夏南海季风低压发展的数值试验

NUMERICAL EXPERIMENT ON DEVELOPMENT OF MONSOON DEPRESSION OVER THE SOUTH CHINA SEA IN EARLY SUMMER

本文用热带有限区域σ—坐标六层初始方程数值预报模式对1979年6月下旬一次南海季风低压的发展过程进行了数值模拟,试验结果表明,本例南海季风低压的发展对大地形不敏感,与南海台风的数值试验结果不同.削减湿度场的试验表明,季风低压的发展与大气中水汽含量密切相关,湿度减小,季风低压发展缓慢甚至发展不起来.积云对流过程及其潜热的释放对季风低压发展有显著影响,它使得低压区的上升运动加强.改变低压南侧的西南风强度,导致水汽及能量输送的减小,不利于低压的发展.低压的发展主要由积云对流所驱动.

This paper gives a successful numerical prediction (24h and 48h ) for the development process of monsoon depression over the South China Sea . A series of numerical experiments has been done . The results show that the influence of topography is little. But other experiments including reducing moisture, cancelling cumulus convection process and weakening the southwesterlies to the south of the depression produce a decaying result of the depression . It is also found that the development of depression is basically driven by the cumulus convection process.