Wave-CISK in Mass Flux Form

Abstract

A reformulation of wave-CISK shows that gravity waves generated by the divergence of cumulus mass fluxes am responsible for the forcing of further convection. When downdrafts are included, a new, non-propagating instability arises. This mode has a growth rate much larger than the usual, propagating wave-CISK mode, but requires the downdraft mass flux to exceed a certain critical value. The nonpropagating mode apparently corresponds to air-mass thunderstorms, whereas the propagating mode suggests long-lived convection. The two modes respond very differently to wind shear.