On the role of mean meridional circulations in the energy balance of the atmosphere

The poleward energy flux in the atmosphere over the Northern Hemisphere is first discussed. The flux associated with the mean meridional circulations is computed and compared with the calculations of the eddy flux. The results indicate a great difference between the tropics and the extratropics with respect to the mechanism of the flux: south of about 30° N the mean meridional circulations are the principal flux agency, whereas eddies dominate at higher latitudes. The total flux is compared with the mean meridional distribution of the heat sources and sinks of the atmosphere. Satisfactory agreement is found, particularly regarding the annual mean conditions.

The role of mean meridional circulations in the hemispheric balance of kinetic energy is found to be small in summer but relatively large in winter, when they seem to be important, especially for the maintenance of the kinetic energy of the mean motion.