1998年7月21日武汉暴雨小尺度动力特征的数值模拟研究

利用三维完全弹性积云数值模式,模拟了1998年7月21日武汉暴雨期间强降水积云的发生、发展过程.着重分析了积云动力学特征以及近地层散度场、水汽通量等对积云降水的发展、维持的贡献.结果表明,特殊的温、湿层结配置是这次强降水对流云发生的主要原因,而近地层高温、高湿气体源源不断地向云体输送,是强降水积云长时间维持的能量来源.合适的上下层风切变,特别是近地层逆向云体风速的存在,使得云体移动前方下层高温、高湿气体向云内输送,云后部伴随降雨而出现的干冷出流迅速流出,上层高空急流的存在,为积云顶部出流在更大范围扩散提供了条件.散度场、水汽通量场的分布及演变,也进一步证明了上述结论.

A Numerical Research on Rain Storm Kinetic Process of the Wuhan Area on July 21, 1998

A three-dimensional non-hydrostatic convective cloud numerical model with fully elastic primitive equations was used to simulate the occurrence and development of the rain-storm in Wuhan, on July 21, 1998. The characteristics of cloud kinetic process and physical quantity flux are analyzed. The results indicate that the special vertical distribution of temperature and humidity is the major cause of this rain-storm. The transport of air with high temperature and humidity from low-level to cloud is the mainly energy source for the development of this rain-storm in a long time. The suitable wind shear, particularly the existence of low-level air flow anti-direction of cloud movement, makes the high temperature and moisture air transport from the front area of cloud at low-level into cloud, and down-wind with dry and low temperature occurring with the rain fall flowing out quickly. Also the upper air jet current supports the flow-out air at the top of convective cloud diffusion far away. This structure of kinetic field maintains the rain-storm for a long time. The analyzed results of divergence field, water vapor flux also furthermore support this conclusion.