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Even though desert dust is the most abundant aerosol by mass in Earth s atmosphere, the relative contributions of the world s major source regions to the global dust cycle remain poorly constrained. This problem hinders accounting for the potentially large impact of regional differences in dust properties on clouds, the Earth s energy balance, and terrestrial and marine biogeochemical cycles. Here, we constrain the contribution of each of the world s main dust source regions to the global dust cycle. We use an analytical framework that integrates an ensemble of global aerosol model simulations with observationally informed constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth (DAOD). We obtain a dataset that constrains the relative contribution of nine major source regions to size-resolved dust emission, atmospheric loading, DAOD, concentration, and deposition flux. We find that the 22 29 Tg (1 standard error range) global loading of dust with a geometric diameter up to 20 um is partitioned as follows: North African source regions contribute 50% (11 15 Tg), Asian source regions contribute 40% (8 13 Tg), and North American and Southern Hemisphere regions contribute 10% (1.8 3.2 Tg). These results suggest that current models on average overestimate the contribution of North African sources to atmospheric dust loading at 65 %, while underestimating the contribution of Asian dust at 30 %. Our results further show that each source region s dust loading peaks in local spring and summer, which is partially driven by increased dust lifetime in those seasons. We also quantify the dust deposition flux to the Amazon rainforest to be 10 Tg yr1, which is a factor of 2 3 less than inferred from satellite data by previous work that likely overestimated dust deposition by underestimating the dust mass extinction efficiency. The data obtained in this paper can be used to obtain improved constraints on dust impacts on clouds, climat

Even though desert dust is the most abundant aerosol by mass in Earth s atmosphere, the relative contributions of the world s major source regions to the global dust cycle remain poorly constrained. This problem hinders accounting for the potentially large impact of regional differences in dust properties on clouds, the Earth s energy balance, and terrestrial and marine biogeochemical cycles. Here, we constrain the contribution of each of the world s main dust source regions to the global dust cycle. We use an analytical framework that integrates an ensemble of global aerosol model simulations with observationally informed constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth (DAOD). We obtain a dataset that constrains the relative contribution of nine major source regions to size-resolved dust emission, atmospheric loading, DAOD, concentration, and deposition flux. We find that the 22 29 Tg (1 standard error range) global loading of dust with a geometric diameter up to 20 um is partitioned as follows: North African source regions contribute 50% (11 15 Tg), Asian source regions contribute 40% (8 13 Tg), and North American and Southern Hemisphere regions contribute 10% (1.8 3.2 Tg). These results suggest that current models on average overestimate the contribution of North African sources to atmospheric dust loading at 65 %, while underestimating the contribution of Asian dust at 30 %. Our results further show that each source region s dust loading peaks in local spring and summer, which is partially driven by increased dust lifetime in those seasons. We also quantify the dust deposition flux to the Amazon rainforest to be 10 Tg yr1, which is a factor of 2 3 less than inferred from satellite data by previous work that likely overestimated dust deposition by underestimating the dust mass extinction efficiency. The data obtained in this paper can be used to obtain improved constraints on dust impacts on clouds, climat

Even though desert dust is the most abundant aerosol by mass in Earth s atmosphere, atmospheric models struggle to accurately represent its spatial and temporal distribution. These model errors are partially caused by fundamental difficulties in simulating dust emission in coarseresolution models and in accurately representing dust microphysical properties. Here we mitigate these problems by developing a new methodology that yields an improved representation of the global dust cycle. We present an analytical framework that uses inverse modeling to integrate an ensemble of global model simulations with observational constraints on the dust size distribution, extinction efficiency, and regional dust aerosol optical depth.We then compare the inverse model results against independent measurements of dust surface concentration and deposition flux and find that errors are reduced by approximately a factor of 2 relative to current model simulations of the Northern Hemisphere dust cycle. The inverse model results show smaller improvements in the less dusty Southern Hemisphere, most likely because both the model simulations and the observational constraints used in the inverse model are less accurate. On a global basis, we find that the emission flux of dust with a geometric diameter up to 20 um (PM20) is approximately 5000 Tg yr1, which is greater than most models account for. This larger PM20 dust flux is needed to match observational constraints showing a large atmospheric loading of coarse dust. We obtain gridded datasets of dust emission, vertically integrated loading, dust aerosol optical depth, (surface) concentration, and wet and dry deposition fluxes that are resolved by season and particle size. As our results indicate that this dataset is more accurate than current model simulations and the MERRA-2 dust reanalysis product, it can be used to improve quantifications of dust impacts on the Earth system.