Assessing conditions favoring the survival of African dust-borne microorganisms during long-range transport across the tropical Atlantic†

Abstract

Forward trajectories of trans-Atlantic dust plumes were studied over a 14 year period (N ∼500 000) with a focus on ambient meteorological conditions affecting the survivability of the microorganisms co-transported with dust. Major dust transport patterns that emerged from the ensemble of trajectories closely follow the established seasonal transport patterns of African dust over the tropical Atlantic Ocean: summer transport (June–August) reaching the southeastern US and the Caribbean at an average altitude of 1600 m and winter transport (December–February) reaching the Amazon basin at around 660 m. Summer trajectories take on average 270 hours to cross the Atlantic, while winter ones take 239 hours. A higher diversity is expected in microorganisms co-transported to the Amazon due to the higher diversity in contributing dust emission sources. Analysis of meteorological conditions along the trajectories indicate more favorable conditions for microorganism survival reaching the Amazon. During the winter and for Amazon trajectories, lower mean solar radiation flux of 294 W m⁻² and mean relative humidity levels at around 61% are observed as compared to averages of 370 W m⁻² solar radiation and 45% relative humidity for summer trajectories entering the Caribbean basin. Nevertheless, 14% of winter trajectories (4664 out of 32 352) reaching the Amazon basin face intense precipitation, potentially removing microorganisms, as compared to 8% of trajectories (2540 out of 31 826) entering the Caribbean basin during the summer. These findings have important implications for the survivability of microorganisms in trans-Atlantic dust plumes and their potential for major incursion events at receptor regions.