THE SENSITIVITY OF NUMERICAL SIMULATION TO OROGRAPHY SPECIFICATION IN THE LOW RESOLUTION SPECTRAL MODEL－PART I: THE EFFECTS OF OROGRAPHY ON THE ATMOSPHERIC GENERAL CIRCULATION

In order to identify the sensitivity of the numerical simulation to the orography specification in a low resolution spectral model, two sets of numerical experiments for full-mountain and no-mountain cases are performed. By comparing the results, it is possible to determine the effects of mountains on the atmospheric general circulation.This is a global, spectral model incorporating the primitive equations segmented by physical parameteriza-tion and mountains, with five equally-spaced sigma levels in the vertical and a triangular truncation at wavenumber 10 in the horizontal.Analysis of results supports earlier work by demonstrating that the low resolution global spectral model is capable of simulating the major features of global general circulation and indicates that it is necessary to consider the effects of mountains on stationary disturbances in the numerical simulation. The simulations show that topography plays an important role in intensifying heat sources for maintenance of disturbances.All the simulation tests indicate that orography has an important influence on the distribution of heat sources and sinks. It reflects that interaction and interrelation exist between the effects of orography and heat sources and the atmospheric circulation via the dynamical processes of atmosphere. This result confirms the view points proposed by Yeh and Zhu (1958), but differs from those by Kasahara and Washington (1971), Manabe and Terpstra (1974).