Numerical Simulation Of A Strong Tornado In Eastern China With Different Microphysical Schemes

A tornado that occurred in eastern China on 23 June 2016 was simulated with the Weather Research and Forecasting(WRF)model(version 3.9)using three different microphysical schemes [WRF single-moment 6-class(WSM6)scheme,Morrison double-moment scheme and Milbrandt–Yau(MY)scheme].The results showed that the Morrison scheme's simulation result was the best among the three schemes,while the WSM6 and MY schemes were able to simulate weak tornado-like vortices in a specific region.The Morrison scheme produced a better structure of three layers,including a cold pool near the ground,thick heating layer in the middle levels,and cooling again above 14 km.The mass and heat budget analysis of the cloud microphysics scheme for the severe convection system shows that water vapor condensation is the main source term and heating term of the water condensate.Three kinds of schemes,a wide range of water vapor condensation process as monomers provides the upward movement of the main energy,in Morrison,the strong cold pool water evaporation formed near the ground,the water vapor condensation and the strong mixing from the rapid evaporation,strong energy conversion in the dragon coils inside,in the other source sink term,under the joint action of a strong development;In the other two schemes,weak ground evaporation is not conducive to convection excitation.From the microphysical processes,the possible formation mechanism was that the convective activity was first evoked by the near-ground cold pool,and then the horizontal vortex tube was raised and vertically stretched before turning in the vertical direction by the release of latent heat caused by the water vapor condensation.Thereafter,the vortex tube was cut off by the downward movement caused by the cloud water evaporation and the snow melting in the front of the convection system,causing the violent vertical lift of the rear vortex tube,forming the tornado.