Developments of the Orthogonal Curvilinear Terrain-Following Coordinate: the New Basis Vectors

Tuesday, 16 December 2014
Jinxi Li1, Yiyuan Li1 and Bin Wang1,2, (1)IAP Insititute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, (2)Center for Earth System Science, Tsinghua University, Beijing, China
We have developed the orthogonal curvilinear terrain-following coordinate (OS-coordinate) proposed by Li et al. (2014), especially focusing on the restriction of the time step in the OS-coordinate. We first propose two new methods to solve the basis vectors of the OS-coordinate, both of which avoid the spatial rotation proposed by Li et al. (2014), therefore simplifying the solving procedure of the OS-coordinate. Moreover, for the major drawback of the OS-coordinate, which is the convergence and the divergence of the grid-lines pointed out by Li et al. (2014), we revise their basis vectors and design a new general rotation parameter to create the new basis vectors of the OS-coordinate. The experimental results show that using these new basis vectors, we can improve the orthogonality of the 3-D coordinate surfaces of the OS-coordinate. More importantly, we can easily control the distance between the neighbour grid-lines, therefore alleviating the restriction of the time step in the OS-coordinate. These have been validated by the idealized Schär-type advection experiments.