Abstract: By the method suggested by Dorodnitsizn a solution of the simultaneous non-linear differential equations for the thermal convection are obtained.The rapid dissipation of cumulus is investigated.The cumulus dissipation starts from the cloud top and propagates rapidlv downward.In this case the effects of non-linearity and unstable stratification are important.It is pointed out that the downdraft is a chief feature in the cumulus dissipation.