Systematic identification of Saharan Air Layer events over the tropical North Atlantic Ocean

Every year, strong north African winds across the Sahara loft dust particles and advect them westwards within the Saharan Air Layer (SAL). These plumes of dust often reach the Caribbean Sea and can heavily affect regional weather patterns by suppressing convective initiation and maintenance. On occasion, SALs even affect the Gulf of Mexico and the continental United States. When concentrations are high, decreased rainfall can yield negative societal and ecological impacts, potentially leading to drought. The Puerto Rican early rainfall season (ERS), spanning from 1 April through 31 July, overlaps with the Saharan dust migration periods, and systematically detecting instances of SAL activity near the island is important for understanding longer-term drought-forcing trends in the region. The resulting dataset, which incorporates MERRA-2 Reanalysis data from 1980–2023 for the ERS months, reveals high variability in both SAL plume frequency and intensity throughout the tropical Atlantic during the April-July periods. Moreover, the frequency of ERS SAL dust plumes increased over the 44-year study period at a rate of 0.5 days a year. However, the regions of maximum frequency vary annually, but are mostly centered in the eastern tropical Atlantic. Machine learning tools were also used to assess SAL morphology and implications for SAL behavior. This study builds an objective database of SAL plumes that can be used to assess the vulnerability of Caribbean islands to dust activity, determine their role as a hydrometeorological forcing mechanism, enable future projections for SAL plume frequency, and ascertain prototypical SAL migration across the Atlantic.