Observational And Numerical Simulation Study Of Dynamical Mechanism Of Inertial Gravity Waves In Hail Storm Processes

Based on the observation of the inertial gravity waves in hailstorm processes in Guizhou Province a theritical and numerical simulation study was made.Through the detection we find that atmosphere gravity waves, as displaying significant behavior law, are stronger in winter-spring than in summer-autumn, with abrupt weakens/strengthens in May/October , and more vigorous at night than during daytime especially those of the short-periods when without distinguished weather process. The waves of 40-80 min periods are strongest of all on a time average basis. Using the parameterization of cumulus convection and expansion of Taylor equation, the isolated wave solution is derived from the nonlinear Kdv equation of inertial gravity waves (IGWs) under the conditions of baroclinic atmosphere and cumulus convection heating for explaining the features of IGW according to observation records. The results show that the IGW's strength is increased with growing of the vertical wind shear and that the jet stream is the most important IGW's source and the prime cause that the IGWs is stronger in winter-spring than in summer-autumn. The Asian jet stream southward shift in October and northward jump in May is the cause of IGW abrupt strengthening in October and weakening in May, respectively, while underside the jet stream is excited the strongest IGW. Normally, the strength ofIGW is proportional to the absolute vorticity, the buoyancy frequency (N~2) and thefrequency of IGWs, which may be regard as the reasons why the IGWs are stronger in the night than in daytime when without distinguished weather process and why the strength of IGWs with periods 40-80 min is stronger than that with periods 140-160 min. The strength of IGW is also proportional to the nonlinear cumulus convection parameter b and Coriolis parameter f. A hail storm process was simulated by using the mesoscale numerical model of WRF in Puding county of Guizhou province and the results of the simulation were analyzed by using Morlet wavelet method.And the result shows that characteristics of the spatial-temporal distribution of IGWs.After more,from the studies of observation and dynamics factors of IGWs and weather system, the dynamics mechanism of IGWs can be shown in this paper. The IGWs with short periods are strengthened in each 1～4 hour before the hail storm.The results of the simulation show that in the upper troposphere ,the IGWs with short/long periods are weaker/stronger before hail storm than that after hail storm. The periods of IGWs with long periods have a obviously shortening after the hail storm.The IGWs are strengthened along with the height.