Diagnostic evaluation of the mean meridional circulation

Summary We evaluate the mean meridional circulation for the Northern and Southern Hemispheres, working with the angular momentum and the mass conservation equations. We derive and equation for the mass stream function on the lines at constant angular momentum and we numerically integrate this equation using the annual mean data related to the periods 1958 through 1963, and 1963 through 1973, as published by Oort and Rasmusson (Atmospheric Circulation Statistics, NOAA Prof. Pap. No., 5 (Rockville, MD, 1971)) and Oort (Global Atmospheric Circulation Statistics, 1958–1973,NOAA Prof. Pap. No. 14 (Rockville, MD, 1983)), respectively. In both hemispheres we find a weak polar cell, a rather intense Ferrel cell and a strong Hadley cell. The values of the intensity of the polar and Ferrel cells are accurately computed, while we are not confident on the numerical values of the intensity of the Hadley cell. because its rising branch is confined in a narrow region close to the Equator where our results are sensible to small variations in the data. Comparison with previous calculations are discussed.