ON THE INFLUENCE OF THE MEAN MERIDIONAL CIRCULATION ON THE ZONAL FLOW

Abstract

The mean meridional circulation calculated earlier from observed values of transports of momentum and sensible heat by solving the zonally averaged form of the quasi-geostrophic omega equation is used to investigate the influence of this secondary flow on the zonally averaged values of the wind and temperature in the atmosphere. The contributions from the horizontal transport processes and the mean meridional circulations are computed separately in order to estimate their relative importance. It is found that the mean meridional circulation counterbalances the horizontal transport of momentum in the upper troposphere, while the two effects work in the same direction in the lower part of the atmosphere. With respect to changes in the zonally averaged temperature field, it is found that the effect of the mean meridional circulation opposes the effect of the horizontal transport of sensible heat almost everywhere. The recent results of calculations of the mean meridional circulation are also used to discuss the role of zonal heating and friction in quasi-geostrophic models.