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

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 maximum 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 developmen of vortex. The role of the terms of vorticity horizontal advection and horizontal convergence-divergence is confined in the mid and low atmosphere, 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.