New information is needed about the potential sources and pathways of trans-Atlantic dust plumes. Such knowledge has important implications for the long-distance transport and survivability of microorganisms. Forward trajectories of trans-Atlantic dust plumes were studied over a 14-year period, between 2008 and 2021 (n =>500,000 trajectories). Two major dust transport patterns emerged from these analyses. First, summer trajectories (June – August) that arrive in the southeastern regions of the United States and the Caribbean basin and travel above the marine boundary layer at an average altitude of 1,600 m. Second, winter trajectories (December – February) that arrive in the Amazon basin and travel within the boundary layer at an average altitude of 660 m. Ambient meteorological conditions such as solar radiation and relative humidity along dust trajectories suggest a more suitable condition for the survivability of microorganisms reaching the Amazon during the winter with a lower mean solar radiation flux of 294 W m-2 and mean relative humidity levels at around 61% as compared to averages of 370 W m-2 solar radiation and 45% relative humidity for summer trajectories intruding the Caribbean basin. Nevertheless, 14% of winter trajectories (4,664 out of 32,352) reaching the Amazon basin face intense precipitation of higher than 30 mm and get potentially removed as compared to 8% of trajectories (2,540 out of 31,826) intruding the Caribbean basin during the summer. Collectively, our results have important implications for the survivability of microorganisms in trans-Atlantic dust plumes and their potential for major incursion events at receptor regions.

Mineral dust is among the top contributors to global aerosol loads and is an active element in the Earth system. Ability of non-photosynthetic vegetation (NPV) to suppress dust emission has been supported by observations and small-scale studies, but current regional to global scale models fail to include NPV in the vegetation coverage input. In this study, we implemented a satellite-based total vegetation dataset, which included NPV, into a regional atmospheric chemistry model and conducted simulations of the entire year 2016 for the conterminous United States. We also conducted a control simulation using only the photosynthetic vegetation (PV) to analyze the effects of NPV on dust emissions. Above 10% decreases in simulated dust emissions are seen over most of the southwestern United States from spring to autumn due to NPV. Reductions in dust concentrations are the largest in spring, and when compared to observations, attenuate the overpredictions of fine soil concentrations at over 93% of the observation sites in the western U.S. Further analyses of essential parameters to the inclusion of NPV indicate that sheltering the surface and increasing the threshold velocity through drag partitioning are major mechanisms for the suppression of dust emissions. On the other hand, NPV causes the friction velocity to increase by more than 10% over most erodible lands during autumn and winter, which can amplify the dust flux. This study highlights the necessity of including NPV into the dust model and states that uncertainty analyses of total vegetation datasets are important.