重庆2次西南涡暴雨过程的类比分析

Analogy on the two cases of southwest vortex rainstorms in Chong Qing

基于AREM模式分别对2010年夏季发生在重庆的两次西南涡暴雨过程进行数值模拟,并利用模拟结果对暴雨过程的动力和热力场演变以及涡度收支变化进行分析。结果表明:1)西南涡造成的降水落区位于低涡中心附近,整个降水过程雨带分布与低涡移动路径相一致;2)整层水汽通量辐合极值出现时间超前于最大降水出现时间,降水增强阶段,整层水汽呈增长趋势,说明存在稳定的水汽输送;3)最强辐合出现时间略早于最大正涡度出现的时间,说明大气辐合能够促进涡度的发展,辐合中心比正涡度中心位置低;4)涡度辐合辐散项对低涡的发展加强起最主要的作用;涡度平流项和涡度辐合辐散项的作用集中体现在中低层大气中,而垂直对流项和扭转项的作用则在中高层更为明显;降水的强弱与涡度变率的大小及伸展高度相对应。

Based on the AREM model, numerical simulations are conducted for two southwest vortex rainstorms in the summer of 2010 in Chongqing, and the evolution of dynamic and thermal physical quantities in the heavy rain events is analyzed by using the simulation results. The results are as follows. 1） Southwest vortex rainfall occurs in the near of the vortex center, and the precipitation rainband distribution associated with the entire event is consistent with the low vortex moving path. 2） The layer-total moisture convergence maximum occurs in advance to the maxi-mum precipitation. The precipitation increases with the layer-total moisture, which indicates that there is the stable supply of water vapor. 3） The strongest convergence appears earlier than the maximum value of vorticity implying that convergence enhances the development of vorticity. The convergence center is lower than positive vorticity center position. 4） The term of convergence-divergence of vorticity plays the main role in the de-velopment of vortex. The role of the terms of vorticity horizontal advection and horizontal convergence-divergence is confined in the mid and low at-mosphere, while the role of the vertical advection item was more evident in the upper-level. The intensity of rainfall corresponds to the variability and the stretching height of vorticity.