Atmospheric Chemistry and Physics | 2021
Improved representation of the global dust cycle using observational constraints on dust properties and abundance
Abstract
Abstract. Even though desert dust is the most abundant aerosol by\nmass in Earth s atmosphere, atmospheric models struggle to accurately\nrepresent its spatial and temporal distribution. These model errors are\npartially caused by fundamental difficulties in simulating dust emission in\ncoarse-resolution models and in accurately representing dust microphysical\nproperties. Here we mitigate these problems by developing a new methodology\nthat yields an improved representation of the global dust cycle. We present\nan analytical framework that uses inverse modeling to integrate an ensemble\nof global model simulations with observational constraints on the dust size\ndistribution, extinction efficiency, and regional dust aerosol optical\ndepth. We then compare the inverse model results against independent\nmeasurements of dust surface concentration and deposition flux and find that\nerrors are reduced by approximately a factor of 2\xa0relative to current\nmodel simulations of the Northern Hemisphere dust cycle. The inverse model\nresults show smaller improvements in the less dusty Southern Hemisphere,\nmost likely because both the model simulations and the observational\nconstraints used in the inverse model are less accurate. On a global basis,\nwe find that the emission flux of dust with a geometric diameter up to 20\u2009 µ m (PM 20 ) is approximately 5000\u2009Tg\u2009yr −1 , which is greater than most\nmodels account for. This larger PM 20 dust flux is needed to match\nobservational constraints showing a large atmospheric loading of coarse\ndust. We obtain gridded datasets of dust emission, vertically integrated\nloading, dust aerosol optical depth, (surface) concentration, and wet and\ndry deposition fluxes that are resolved by season and particle size. As our\nresults indicate that this dataset is more accurate than current model\nsimulations and the MERRA-2 dust reanalysis product, it can be used to\nimprove quantifications of dust impacts on the Earth system.