SEASONAL-VARIATION OF TROPICAL CIRCULATION AS SIMULATED BY A GLOBAL MODEL OF ATMOSPHERE

A mathematical model of the atmosphere with a seasonal variation of insolation and sea surface temperatures is integrated numerically with respect to time over three model years. The model has a global computational domain and a realistic distribution of mountains. It contains a highly idealized parameterization of convection, i. e. dry and moist convective adjustment. It is found that the model accurately simulates the seasonal variation of the location of the tropical rainbelt as well as that of the flow field associated with it. Over the continental regions of the model, the tropical rainbelt tends to form very close to the equator, whereas, in certain oceanic regions, it has a tendency to form away from the equator. Based upon a comparison of these results with those of another numerical experiment, it is concluded that this tendency is not due to an inherent characteristic of the rainbelt of the model to avoid the equator in oceanic regions, but rather it is due to the equatorial belt of low sea surface temperatures which is not favorable for the formation of a rainbelt. Over the sea, the surface temperature distribution seems to be the primary factor in determining the location of the rainbelt and accompanying tropical disturbances.