It has been recognized recently that the role played by organized cumulus-scale convection is very important in understanding the dynamics of the general circulation of the atmosphere, particularly in the tropics. Because of large differences between the size of cumulus-scale convection and of large-scale motion, it is difficult to deal with both phenomena in one system of atmospheric equations. In this paper we discuss (1) the effects of an ensemble of convective elements on the large-scale motion, and (2) the influence of the large-scale motion on the development of organized cumulus clouds. A scheme is proposed to solve simultaneously two systems of equations for the large-scale flow and for the cumulus-scale convection. The effects of cumulus convection are included in the equations for the large-scale motions. The largescale (synoptic) conditions are included in the equations for the cumulus convection which determine not only the structure of cumulus clouds, but also the population of the clouds.