Convective Fluxes in Tropical Cyclones

Abstract

Vertical fluxes of mass, static energy and angular momentum in tropical cyclones and their environments are analyzed using composite rawinsonde data. Cumulus-scale eddy fluxes are derived using a spectral cloud model incorporating the effects of downdrafts, overshoot cooling, multiple-level cloud detrainment and ice-phase transitions. Deep convection exists in all regions in approximately direct proportion to the low-level mass convergence, and large amounts of shallow cloudiness are found everywhere. A bimodal cloud distribution is found only in the outer convective area. Direct warming of the troposphere through cloud-induced subsidence is very small in the upper troposphere inside a radius of 4° latitude. Angular momentum appears to be conserved in deep and middle-level convection, while shallow clouds and dry turbulence transport momentum downward in the lower levels. These principles could be incorporated into cumulus parameterization schemes.