convergence and divergence

convergence and divergence, in meteorology, the accumulation or drawing apart of air, as well as the rate at which each takes place. The terms are usually used to refer specifically to the horizontal inflow (convergence) or outflow (divergence) of air. The convergence of horizontal winds causes air to rise, whereas the divergence of horizontal winds causes downward motion of the air (subsidence). Ground-level atmospheric pressure is not affected by convergence if divergence of an equal magnitude occurs simultaneously at higher levels.