A global model with overlapping mercator and stereographic grids

A global nine-layer primitive equation model is developed to investigate the dynamic and thermodynamic influences of plateaus and high mountains on the atmospheric circulation. Besides topography, the effects of solar radiation, longwave radiation, large-scale condensation, cumulus convection and surface fluxes of heat momentum are also included in the model. In order that the finite-difference approximations represent fairly accurately the circulation in both higher and lower latitudes, we use Mercator projection in lower latitudes and Stereographic projection in higher latitudes.The simulated sea level pressure, wind field, precipitation distribution and vertical circulation in summer and winter are given, respectively, and they are compared with the observations.