Numerical Simulation Of A Severe Convection Event Over Inhomogeneous Underlying Surface

The study of the trigger,oraganization and evolution of severe convective weather systems has been a frontier issue in mesoscale weather research.It's also a practical problem in current weather prediction because of its complexity.This paper pays atention to the influence of a severe precipitation process by nonuniform underlying serface under the affection of Meiyu Front.Four sensitvity experiments with high-resolution numerical simulation concerning underlying serface are designed and compared in order to analyse the macanics of the influence of underlying serface to a sever weather system.The result shows that,the influencd by the land and sea underlying serface is mainly caused by the dynamic and thermal differences between the land and sea.The land and sea breeze is favor of the genesis of the convergence zone in the low-level atmosphere around the costal areas.The convergence leads to the updraft of the air and increases the low-level wind shear which proveides dynamic conditions for the genesis and strengthening of sever weather system.The wind from the sea transport water vapor to land which provides favorable water vapor conditions.On the other hand,the land and sea breeze accelerate the exchaging of air mass from the sea with which from the land and stablize the boundary layer.The underlying land warms rapidly during the day.The low-level sensible heating flux keeps strengthening before mid-day which leads to the gathering of convective available potential energy.In the favorable conditions,convective systems rapidly develops.Three of the sensitivity experiments all show that the larger the land size is,the larger the sensible and latent heating flux will be which leads to the development of convection and the boundary layer.The topography leads to a two-way influenc to the front rainband.On the one hand,the topography changes the wind by the barrier in the low-level which decreases the southen wind in the costal area.Also,the friction caused by topography weakens the convective system and lowers the boundary layer.On the other hand,the topography slows the rainband so that the rainband may updraft long enough and get strengthened.