湿斜压大气中暴雨中尺度系统发展的一种可能机制

根据暴雨中尺度系统发生时的大气运动特征,在绝热、无摩擦条件下,从湿斜压原始方程出发,考虑大气运动的涡度及散度演化不仅受动力场的制约,而且还受到热力场的约束,采用不同于传统研究涡度及散度方程的分析方法,导出了新形式的涡度及散度方程。在此基础上,分析了湿斜压大气中对流层中低层气流旋转与辐合持续增长的动力特征,初步揭示了湿斜压大气中暴雨中尺度系统发展的动力机制。

A Mechanism of Mesoscale Heavy Rain System Development in Moisture Baroclinic Atmosphere

Torrential rain and flood are the main disasters of meteorology in China in summer.So meteorology workers pay close attention to the cause of torrential rain and the forecast of it.Our level of understanding heavy rain process is low because of the complex nature of heavy rainfall formation.It is imperative to enhance research on the formational and development mechanism of the mesoscale vortex systems.According to divergence and vorticity fields evolution restricted by not only dynamic fields but also thermodynamic fields in adiabatic and non-frictional atmosphere,new typical divergence and vorticity equations are obtained by means of thermodynamic equation led into traditional divergence and vorticity equations.Dynamic property of low-level convergence and cyclone vorticity growth is analyzed on basis of new equations.Dynamic mechanism of mesoscale heavy rain system development in moisture baroclinic atmosphere is revealed.The results show that the reactions and overlap between low-level warm(moisture) disturbance from the south and high-level cold(dry) air mass from the north lead to quickly development of mesoscale heavy rain systems in instable stratified atmosphere. A typical case is that the low-level jet in combination with high-level trough often leads to the formation and development of meso-scale heavy rain systems in summer.