Diagnostic Analysis of Vorticity Equation of a Torrential Rainstorm Process in Henan in 2009

doi:10.3969/j.issn.1673-7148.2012.04.003

Abstract：Using NCEP/NCAR reanalysis grid data, conventional meteorological data and mesoscale WRF model, a torrential rainstorm process on August 28 to August 30, 2009 in southern Henan is simu-lated and diagnosed. The results show that the effect of the simulation results of the torrential rainstorm is well. The simulated physical quantities can reflect the actual characteristics of the the torrential rain- storm. The intensity and location of the rainstorm is consistent with the fact. The upper trough, the sub-tropical high, super low-altitude easterly jet and low-level wind shear are the main effect system. This pa-per made use of the method of vorticity equation to analyze diagnostically the rainstorm process. The vor-ticity advection and the convergence and divergence of the vorticity equation are the main dynamic condi- tions. The vertical transportation and tilting items of the vorticity equation take small contribution to the vorticity change. The vorticity advection plays a positive contribution to the vorticity local change in mid- dle and low-level. The vertical transportation, tilting items, and convergence and divergence play a nega-tive contribution to the vorticity change. The vorticity advection makes the middle and low-level cyclonic rotation stronger, which is beneficial to the convergence stronger in the middle and low-level and local vorticity increase. And the others make the convergence weaken and vorticity decrease. Using the simula-tion produce of vertical helicity and so on to diagnose the rainstorm process, result shows that the center of the rainstorm corresponds to the large value center of the vertical helicity, the negative value center of water vapor flux divergence. The torrential rainstorm was occurred in the good dynamic, water vapor and heat conditions.