The influence of exchange of sensible heat with the earth’s surface on the planetary flow

The exchange of sensible heat with the earth’s surface is one of the most important external forces which influence the motion of the atmosphere. This is studied with the aid of a linearized model, where the heating is assumed to be proportional to the difference between the temperature of the air at the bottom of the atmosphere and the temperature of the underlying surface. Since the temperature of the air is one of the dependent variables. the heating is dependent on the motion. The vertical decrease of the heating is given by a power function.

Stationary disturbances on the zonal flow are evaluated for a simple temperature distribution of the ground which corresponds to conditions in middle latitudes in winter, which result from the effects of two continents and two oceans. The resulting horizontal distribution of the heat sources and sinks is evaluated. It is found that the positions of the heat sources are about 30° to the west of the temperature maximum of the underlying surface.

The influence of friction, the vertical variation of the heating and the zonal wind profile are studied separately.

The longitudinal variation of the heating along 45° N is compared with the normal sensible heat transfer in winter estimated from observations. Good agreement is obtained both regarding the magnitude of the heating and the phase difference between the heating and the ground temperature fields.