A multi-model analysis of the transatlantic dust transport, deposition, and optical properties in the AeroCom Phase III

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Abstract. Transatlantic dust from North Africa is the largest intercontinental aerosol flux on Earth, affecting radiative forcing, cloud processes, and biogeochemical cycling, yet the inter-model spread of dust transport remains large in previous AeroCom experiments. With the progress in 17 AeroCom Phase III (P3) models, this study evaluates the transatlantic dust cycle for 2010 against AERONET inversions, satellite products (MODIS, CALIOP, MISR, IASI, POLDER, and MODIS-TIR), DustCOMM, CAMS, MERRA-2, in-situ records, and GPCP precipitation across subregions from North Africa to the Caribbean. We found that AeroCom P3 narrows mid-visible dust optical depth (DOD) diversity to 30–45 % across the transport domain relative to AeroCom P2 (38–59 %), yet this convergence masks compensatory biases, as models with lower (or higher) mass loading may have higher (or lower) mass extinction efficiency (MEE), yielding similar DOD despite a large spread of mass representations. Compared with observational estimates, model biases intensify with transport distance, with median DOD underestimated by ~50 % and ~70 % over mid- and long-range regions, and loss frequencies exceed satellite estimates by a factor of 2–3. Such biases remain unresolved even with super-coarse extensions, indicating that constraining mid-visible DOD alone is inadequate for the dust cycle. The excess removal implicates deficiencies in gravitational settling, wet scavenging, and vertical transport parameterizations. This systematic underestimation could propagate into dust radiative forcing, cloud-dust interactions, and nutrient delivery to Atlantic and Amazonian ecosystems. Progress requires size-resolved benchmarking (DOD at 550 nm and 10 µm with size-segregated mass), non-spherical settling treatments, and mechanisms sustaining coarse particles aloft.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.