Convective Fluxes in Tropical Cyclones

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  • 1 Department of Atmospheric Science, Colorado State University, Fort Collins 80523
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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.

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.

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