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Representation Of Complex Topography In Cartesian Coordinate Atmospheric Meso-scale Numerical Model


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W. Sha & H. Ueda


Representation of complex topography in Cartesian coordinate atmospheric meso-scale numerical model W. Sha1 & H. Ueda2 1 Geophysical Institute, Graduate School of Science, Tohoku University, Japan 2 Disaster Prevention Research Institute, Kyoto University, Japan Abstract We intend to develop an atmospheric meso-scale numerical model, which is expected to suitably treat the steep topography and complex objects on the earth's surface with a finer resolution. In this work, the finite volume method (FVM) in conjunction with the SIMPLER (Semi-Implicit Method for Pressure-Linked Equation Revised) algorithms is used for calculations of the unsteady, three-dimensional, compressible Navier-Stokes equations on a staggered grid. Abandoning the customary terrain-following normalization, we choose the Cartesian coordinate in which the height is used as the vertical one. Blocking-off method is introduced to handle all of the steep topography and complex objects above the earth's sea-mean level. For the spatial and temporal discretizations, higher-order upwind convection scheme is employed, and fully time implicit scheme is utilized. As a preliminary test, the model has been run on flows over a cube mounted on surface. Result of simulations is present, which shows the potential of our proposed approaches for the next-generation atmospheric meso-scale model development. 1 Introduction Since terrain-following vertical coordinate (sigma) system (Phillips 1957; Gal Chen and Somerville 1975) has been used extensively to accommodate orography in models for atmospheric flows, most of existing community meso- scale atmospheric numerical model in the world are using the terrain-following coordinate as the vertical coordinate. However, a problem that has received