Precipitation in the Venezuelan Andes in the context of regional climate

Rainfall regimes are primarily unimodal in central and eastern Venezuela bu t bimodal (peaks in May-June and September-October-November with a minimum in July-August) in the northwest. There is a sharp transition across the An des suggesting a topographic-circulation connection. However, a mid-summer minimum also occurs at other locations in Venezuela and Central America dur ing individual years. This paper addresses the nature and control of the re gimes including the role of large-scale circulation features and convection as indicated by outgoing longwave radiation data. Altitudinal characterist ics of precipitation in the Andes and their spatial variability are also in vestigated. The development of the minimum within the rainy season annual c ycle is shown to be related to the combined effects of the evolution of sea surface temperatures in the east Pacific warm pool and reinforced in the a rea of the Andes by enhanced easterlies during July and August.