Application of Gravity Wave Drag Scheme at the Sloping Area of Tibet Plateau in a Case Study

In this paper,a case study was carried out to find to what extent the numerical simulation results will be affected by turn on the gravity wave drag scheme in Weather Research and Forecasted Model. The case is a continuous heavy rain process in southwest China,and two numerical simulations lasted 120 hours was done to simulate the process. One with the gravity wave drag scheme turned on and another with the gravity wave drag scheme turned off. The difference between two simulations was getting clearer after 48 ~ 72 hours. Values of geopotential height on Tibet Plateau is higher with gravity wave drag scheme than without it. Values of geopotential height at downstream areas of Tibet Plateau is lower with the scheme than without it. The simulated position of a vortex on Tibet Plateau is more precisely with the scheme. And both simulations can depicted an active southwest vortex in Sichuan basin. The position of maximum precipitation are better characterized by the simulation with the scheme,but value of the precipitation are over too much in both simulations. This may because the precipitation process is so complicated and gravity wave drag scheme is not the key point to influencing the result. Also,the scheme cannot make much influence on temperature and surface pressure. Overall the result with gravity wave drag scheme is slightly better. It need to admit that this is only a case study and have its uncertainty. The applicability of the scheme is sure need to have a long-term test in the in subsequent work.