Following Wu and Chen (1989), in terms of the mean meridional circulation function elliptical differential equation similarin form to that developed by Kuo (1956) and by use of time average statistics of the atmospheric circulation in the wave number domain atthe same time intervals, a study is made of the contribution of the in-ternal forcing of the atmosphere on two space scales to the mean meridi-onal circulation. Results show that the planetary waves have a con-siderable influence on the intensity of the upper center of the bi-Hadleycell and, in contrast, the synoptic-scale waves exert vital effects on the Ferrel cell. In the NH such internal forcings by the planetary andsynoptic-scale waves make much the same contributions to the mean meridional circulation whereas in the SH the latter contribute far morethan the former. Further more, in the northern winter (summer) the contribution of heat (angular momentum) transport of the planetary waves allows the descending (ascending) branch to occur as far as around 40°N, a very important contribution to the winter (summer) monsoon circulation in East Asia.