Mesoscale Numerical Simulation And Diagnostic Analysis Of A Torrential Rainstorm Process In Southern Henan In2009

Using Mesoscale WRF model, Conventional meteorological data and NCEP/NCAR Reanalysis data, a torrential rainstorm process in August28to August30in Henan is simulated and diagnosed by the equation of Potential Vorticity budget and Vorticity Equation.Using the high-resolution simulation results by the model to study the physical mechanism, the large-scale circulation, water vapor, dynamic conditions and thermal conditions. The main conclusion includes:1、By the analysis of the large-scale circulation and low level jet,we find that the upper trough and the subtropical high are the main circulation pattern of the torrential rainstorm process. The cold air and low level jet are the main weather system.Beneficial circulation situation and temperature conditions and moisture conditions are the main factor to the development and strengthen of the rainstorm.2、The simulation results of the accumulated precipitation and circulation pattern and physical quantities are contrasted to the actual.The results show that the simulation result of this model that simulated the torrential rainstorm process is preferred. The simulated direction of movement of the precipitation and the precipitation area and the precipitation intensity are close to the actual one. The simulated circulation pattern is consistent to the actual too.The simulation circulation can characterize the atmospheric circulation features of the torrential rainstorm process. In addition, the simulation distribution and value and change trend of temperature and the water vapor flux are consistent with the real atmosphere. Therefore,the simulation results by this model are reliable.The high-resolution data of the model can be used to diagnose the torrential rainstorm process.3、To diagnostic the rainstorm process, this paper made use of the method of vorticity equation. Vorticity advection and the convergence and divergence of the vorticity equation are the main dynamic conditions.But the two aspects are counterproductive. Vertical transportation and tilting items of the vorticity equation take small contribution to the vorticity change. Vorticity advection play a positive contribution to the vorticity change. Vertical transportation, tilting items and convergence and divergence play a negative contribution to the vorticity change. The low-level vorticity advection in rainstorm regional prompted local vorticity increased,strengthening of the cyclonic circulation and enhancement of the convergence.4、Potential Vorticity budget can well diagnose the characteristics of the dynamic and thermodynamic of the rainstorm. The local changes of Potential Vorticity can characterize the process of rainstorm.The Potential Vorticity in the low-middle atmosphere increaseed with the rainstorm developing. The storm center is constant with the positive area of the local changes of Potential Vorticity. Among the budget various, the latent heat is the main contribution items. The effect of the horizontal advection, vertical transportation and friction is small. The horizontal advection and the latent heat take the positive contribution to the local changes of Potential Vorticity. The role of latent heat make the potential vorticity gradually increased. The horizontal advection is conducive to make the potential vorticity gathered to the flow field convergence zone.The vertical transportation and friction take the negative contribution to the local changes of Potential Vorticity. The vertical transportation can thansfer the Potential Vorticity from the lower to the high-level and reduce the Potential Vorticity in low-level. Under the influence of the friction, the Potential Vorticity in low-level is dissipatived and reduced.5、Using the simulation physical of vertical helicity, Q vector and so on to diagnostic the rainstorm process,result shows that the center of the rainstorm corresponds to the center of the vertical helicity, the convergence center of Q vector, the negative center of water vapor flux divergence. The torrential rainstorm developmented in the good dynamic, water vapor and heat conditions.