On the Maintenance of Zonal Mean Flow

Abstract

Assuming that the longitudi n al phase of each wave component of disturbance takes random values, relations which hold among mean eddy transports have been found in the case of stationary mean. In the middle latitudes, where the horizontal eddy transport of heat is northward, the vertical eddy transport of heat is expected to be upward from one of these relations, causing the transformation from eddy potential energy to eddy kinetic energy. As to the vertical eddy transport of momentum, it seems to be upward not only in low latitudes but also in middle latitudes. This suggests, from the balance requirement of angular momentum, that the downward transport of angular momentum by the frictional effects, in addition to the indirect meridional circulation, cannot be so small in magnitude as hitherto been considered.Combining these relations among eddy transports with the equations for the balance of angular momentum and thermal energy, it has been found possible to express the relation between the distributions of mean zonal flow and heat source. Detailed discussions for this expression are left for future studies, but the observed relation between them can be thus explained at least qualitatively.