Early Summer Rains and Their Mid-Summer Cessation Over the Caribbean: Dynamics, Predictability, and Applications

of a dissertation at the University of Miami. Dissertation supervised by Professor Brian Mapes. No. of pages in text. (103) The annual rainfall cycle in the Caribbean is characterized by a bimodal pattern with peaks in the late spring (“early rainfall season”) and late summer (“late rainfall season”) with a mid-summer minimum (“mid-summer drought”). The time average rainfall pattern during the early rainfall season reveals a distinct southwest to northeast spatial pattern , known as the Caribbean rain-belt, that is similar to other northern hemisphere subtropical rain-belts. A series of Caribbean farmer interviews guided my decision to focus on the dynamics and evolution of the Caribbean rain-belt. Results from farmer interviews reveal that their livelihoods are more vulnerable to variability in the timing and amount of the early season rains rather than variability in the mid-summer drying. Therefore, there is a strong social and economic relevance to understand rainfall dynamics during the Caribbean early rainfall season. The atmospheric dynamics that contribute to the Caribbean rain-belt are diagnosed from the quasi-geostrophic omega equation from daily observations. Forcing for ascent at the upper troposphere is supported by positive zonal wind at 200hPa and jet streaks, while positive temperature advection from the tropics at 500hPa provides forcing for ascent in the mid-troposphere. Moisture availability for the Caribbean rain-belt is regulated by local sea surface temperature and by moisture advection from the tropics in