Impact of height-based terrain-following coordinates on a case of quasi-stationary front simulations around the Tibetan Plateau

Abstract

The GRAPES_Meso model has some forecast problems, such as larger south wind and more false precipitation in the downstream region of the Tibetan plateau. The proper smoothed-level terrain-following coordinate (SLEVE T-F coordinate for short) could efficiently reduce the pressure gradient force error and the mass transport error that are closely related to the wind and water vapor forecasting, therefore, potentially increase prediction performance. Four kinds of T-F coordinates are selected here to simulate a typical quasi-stationary front process. The results of the simulation indicate that under the weak evolution of synoptic background, the improvement of the SLEVE T-F coordinate would be more significant. The SLEVE T-F coordinate can reduce the bias of the wind, false precipitation, false synoptic systems and so on, which results in small calculating error and the better performance of the simulation.

Keywords

• grapes model
• terrain-following coordinate
• quasi-stationary front
• dynamic core
• numerical modelling