Impacts of Local Convective Processes on Rain Water Budgets in a Tropical Island

Multi-scale meteorological influences govern rain budgets in coastal-tropical environments. This study aims to determine the impacts of tropical island processes on local convective storm production. An analysis of the period between 1 June 2015 and 31 July 2016 showed that island-enhanced local convective storms on the west side of the island of Puerto Rico accounted for 89 of 322 storms. While large scale influences such as the El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), African easterly waves, and Saharan dust transport modulate moisture conditions over the Caribbean, analysis of local data from weather stations and the Convection, Aerosol, and Synoptic-Effects in the Tropics (CAST) field campaign in Puerto Rico showed that local island processes can initiate or enhance convective rain events. Analysis of the wind flow, convective available potential energy (CAPE), lifted index (LI), and the bulk Richardson number (BRN), provide evidence of thermal and mechanical forcings on precipitation including surface heating, orographic uplift, and sea-breeze trade-wind convergence. In the presence of these forcings, triggered or modified convection with available precipitable water exceeding 50 mm ultimately enhanced rainfall totals in western storms even amidst intense dust episodes with aerosol optical thickness (AOT) over 0.4. These results may have major implications for considering the impacts of local processes on water budgets in tropical islands.