EFFECTS OF MOUNTAINS ON THE GENERAL CIRCULATION OF THE ATMOSPHERE AS IDENTIFIED BY NUMERICAL EXPERIMENTS.

In order to identify the effects of mountains upon the general circulation of the atmosphere, a set of numerical experiments is performed by use of a general circulation model developed at the Geophysical Fluid Dynamics Laboratory of NOAA. The numerical time integrations of the model are performed with and without the effects of mountains. By comparing the structure of the model atmospheres that emerged from these two numerical experiments, it is possible to discuss the role of mountains in maintaining the stationary and transient disturbances in the atmosphere. The model adopted for this study has a global computational domain and covers both the troposphere and stratosphere. The results of the analysis reveal many important effects of mountains. For example, the probability of cyclogenesis in the model atmosphere increases significantly on the lee side of major mountain ranges where the core of the westerly jet is located. Also, mountains affect the hydrologic processes in the model atmosphere by modifying the field of three-dimensional advection of moisture, and alter the global distribution of precipitation very significantly. In general, the distribution of the model with mountains is less zonal and more realistic than that of the model without mountains.