Water Budget of a Mesoscale Convective System in the Tropics

A squall-line cloud cluster observed in the Global Atmospheric Research Program's Atlantic Tropical Experiment (GATE) is studied as an example of a mesoscale convective system in the tropics. The system is divided into convective and stratiform regions. Composite wind, vertical motion, humidity, radar and satellite data fields have been derived for the system and are used to calculate the components of the water budgets of each region. Particular attention is devoted to understanding the sources of condensate for the stratiform region. The mesoscale updraft in the stratiform cloud accounts for 25–40% of the condensate making up the stratiform cloud, while the remaining 60–75% is supplied by horizontal transfer to the stratiform region of condensate generated in the cumulonimbus towers of the convective region.