Cumulus Convection and Larger Scale Circulations I. Broadscale and Mesoscale Considerations

Abstract

This paper (part I) is a discussion of the magnitude and implication of the vertical circulation patterns of the summertime tropical atmosphere as derived from synoptic scale considerations. Part I is compared to the vertical circulation patterns derived from cumulus scale considerations as discussed by López in part II, a companion paper. From the synoptic scale considerations, we show that a very significant subsynoptic or local vertical motion is occurring within the cloud regions of the Tropies. This mass-cancelling local up- and-down circulation is not resolved by the mean or synoptic scale flow patterns. The magnitude of this local or up- and-down vertical circulation can be estimated from cloud-cluster scale (approx. 4°) mass, vapor, energy, and rainfall-evaporation budgets. Results are closely comparable to those obtained by López from an independent small-scale approach through modelling of individual cumulus elements. This local vertical circulation is shown to be fundamental for the mass, vapor, and energy balances of the tropical atmosphere. Other discussions of the characteristics of the cumulus convective atmosphere are included.