Assessing the Effects of the Saharan Air Layer on Atmospheric Instability and Convective Patterns in the Tropical North Atlantic Ocean during the Puerto Rican Early Rainfall Season

Every spring and summer, strong winds across the Sahara Desert loft dust particles and advect them westwards within the Saharan Air Layer (SAL). These dust plumes often reach the Caribbean Sea and can heavily affect regional weather patterns. Namely, Saharan dust acts as a suppressant to convective processes. The Puerto Rican Early Rainfall Season (ERS), spanning from April through July, overlaps with Saharan dust migration periods. SAL plume episodes during the ERS are common in Puerto Rico with impacts including air quality reductions, poor visibility, and diminished diurnal convective coverage, often lasting no more than 2 days. Prolonged periods of enhanced dust concentrations can create more significant societal and environmental effects, potentially leading to drought. For this study, MERRA-2 reanalysis column-integrated zonal and meridional dust fluxes are used to calculate dust transport across the tropical Atlantic back to 1980. High integrated dust transport (IDT) corridors are objectively identified through size, length, location, and dust-flux criteria to compile a database of Saharan dust outbreaks entilted the Database for Early Rainfall Season Atlantic Dust (DERSAD). This revealed the highest frequency of dust outbreaks in the eastern tropical Atlantic, up to 26.6% of DERSAD days. High variability in SAL plume activity was observed through the reanalysis. In 2015, Puerto Rico and surrounding Caribbean islands experienced an extreme drought, resulting in major water shortages and severe crop loss. This corresponds with the greatest frequency of Saharan dust plumes on record for the Caribbean, up to 564% of the ERS climatological mean. Additionally, 2020 featured several intense Saharan dust plumes, most notably in late June when IDT values were 11 times higher than the daily averages for late June in Puerto Rico. This research intends to build an objective database of SAL events, as well as assess the effects of the SAL on convective instability and precipitation patterns across the Caribbean Sea to assist in preparedness for future drought.