Implementation of the Klemp height-based terrain-following coordinate in the GRAPES regional model: Idealized tests and inter-comparison

A height-based terrain-following coordinate (Klemp coordinate) has been implemented into the GRAPES regional model and compared with the traditional Gal-Chen coordinate and smooth level vertical coordinate (SLEVE coordinate). Idealized tests of the resting-atmosphere and the gravity wave were designed and carried out to assess the model's performance. The results show that the computational errors of pressure gradient force under the Klemp coordinate were mostly reduced in comparison with the other two coordinates. For the gravity wave test, the simulation by using the Klemp coordinate significantly outperformed the others. Moreover, implementation of a generalized Mahrer's approach can further improve the accuracy of the horizontal pressure gradient force.The results of a real case experiment show similar conclusions.