Johnson, R.H., and G.S. Young, 1983

Heat and moisture budgets of tropical mesoscale anvil clouds

J. Atmos. Sci., 40, 2138-2147

Abstract

An analysis of the heat and moisture budgets of tropical mesoscale anvil clouds has been carried out. Mesoscale anvils, defined as widespread (100 km) cloud systems extending from near the freezing level to the high troposphere, are characterized by light, stratiform precipitation. These cloud features, which are preceded by and generally merged with cumulonimbus clouds, are prevalent throughout the tropics and summertime midlatitudes and may account for an important fraction of the total tropical rainfall.

Sounding data from the December 1978 field phase of the International Winter Monsoon Experiment (Winter MONEX) are used to determine heat and moisture (Q1t and Q2) budgets for a number of mesoscale anvil cloud systems. The composite heating (Q1) profile shows a warming peak in the upper troposphere near 350 hPa or 8–9 km that can be attributed to condensation and freezing in the anvil and a cooling peak in the lower troposphere near 700 hPa or 3 km due to rainfall evaporation and melting. The moisture (Q2) budget shows a drying maximum in the upper troposphere coincident with the warming peak and a moistening maximum in the lower troposphere near 800 hPa or 2 km.

The heat budget is compared with that determined recently for mesoscale anvils by Houze (1982), who has used an independent and different approach, and good agreement between the two heating distributions is found. The heating and moistening profiles for mesoscale anvils are considerably different from those determined by large-scale budget studies of entire tropical cloud clusters, which contain both cumulonimbus and mesoscale anvil cloud effects. In particular, the heating profiles diagnosed here show an upward shift in the level of maximum heating, and cooling, instead of heating in the lower troposphere, extending from near the freezing level to the surface.