A computer simulation of the general circulation of the atmosphere for purposes of climatological studies. The atmosphere is contained within a notional three-dimensional grid and its condition described by the gas laws calculated at each point of intersection within the grid. Climatic development is then simulated by repeated recalculations of the effect of changes at one intersection on the intersections surrounding it. Present GCM studies are limited by the coarseness of the grids used, which cannot reflect events, such as cloud formation, occurring on a smaller scale, and by ignorance of the detail of certain important processes, such as those affecting energy transfer between the oceans and atmosphere.