Climate modeling using an equivalent meridional circulation

Numerical integrations of a simple two-layer general circulation model are used to determine the climate of the model, represented by long-term mean values. The response of the model to changes of the solar constant and the angular velocity of the earth is considered. Concerning the effect of the large-scale motions on the mean temperature field, it is shown that the total heating has clearly a more simple meridional variation than any of the parts into which the heating is normally divided. Furthermore it is found that the total heating due to the large-scale motions is reproduced very well by a certain hypothetical meridional circulation, determined from the mean temperature field. By using this equivalent meridional circulation in the thermodynamic equation, a climate model is formulated as an analogue to the general circulation model. The mean temperature fields at the two levels are the only dependent variables, and numerical integrations of the model are carried out very quickly. The results of the integrations show that the steady state solutions obtained simulate very well the long-term mean temperature fields found from the general circulation model.DOI: 10.1111/j.2153-3490.1982.tb01812.x