Dust is an important indicator of climate change. In paleoclimate research, sediments bearing signals of dust deposition offer a rich archive for climate change history. However, the dust‐climate link is very complex due to the various direct and indirect feedbacks in the Earth system. In this study, we examine two issues: (1) given the recent global warming, what are the dust variations, both globally and in key dust regions, and (2) what are the climate drivers behind the variations? Using synoptic data for the period 1974–2012, we analyzed the global trend of dust frequency and visibility‐derived dust concentrations and their characteristics in key dust regions, including North Africa, the Middle East, Southwest Asia, Northeast Asia, South America, and Australia. We also examined the likely climate drivers for dust variations in the different regions by computing the correlations between the time series of dust and of major climate indices—the Multivariate El Niño/Southern Oscillation Index, North Atlantic Oscillation, and Atlantic Multidecadal Oscillation (AMO). It was found that over the period 1984–2012, the global mean (excluding North America and Europe) near‐surface dust concentration decreased at 1.2% yr−1. This decrease is mainly due to reduced dust activities in North Africa, accompanied by reduced activities in Northeast Asia, South America, and South Africa. A significant negative correlation between Saharan dust and AMO was detected, and it seems reasonable to suggest that under present climate, the global dust trend is determined by the climate systems governing the Atlantic and North African regimes.

Abstract. 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 coarse-resolution 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 µm (PM20) is approximately 5000 Tg yr−1, 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.

Abstract. The large uncertainty in the mineral dust direct radiative effect (DRE) hinders projections of future climate change due to anthropogenic activity. Resolving modeled dust mineral speciation allows for spatially and temporally varying refractive indices consistent with dust aerosol composition. Here, for the first time, we quantify the range in dust DRE at the top of the atmosphere (TOA) due to current uncertainties in the surface soil mineralogical content using a dust mineral-resolving climate model. We propagate observed uncertainties in soil mineral abundances from two soil mineralogy atlases along with the optical properties of each mineral into the DRE and compare the resultant range with other sources of uncertainty across six climate models. The shortwave DRE responds region-specifically to the dust burden depending on the mineral speciation and underlying shortwave surface albedo: positively when the regionally averaged annual surface albedo is larger than 0.28 and negatively otherwise. Among all minerals examined, the shortwave TOA DRE and single scattering albedo at the 0.44–0.63 µm band are most sensitive to the fractional contribution of iron oxides to the total dust composition. The global net (shortwave plus longwave) TOA DRE is estimated to be within −0.23 to +0.35 W m−2. Approximately 97 % of this range relates to uncertainty in the soil abundance of iron oxides. Representing iron oxide with solely hematite optical properties leads to an overestimation of shortwave DRE by +0.10 W m−2 at the TOA, as goethite is not as absorbing as hematite in the shortwave spectrum range. Our study highlights the importance of iron oxides to the shortwave DRE: they have a disproportionally large impact on climate considering their small atmospheric mineral mass fractional burden (∼2 %). An improved description of iron oxides, such as those planned in the Earth Surface Mineral Dust Source Investigation (EMIT), is thus essential for more accurate estimates of the dust DRE.

Abstract. 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 µm 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 yr−1, 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, climate, biogeochemical cycles, and other parts of the Earth system.

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Further developments of a parameterization scheme for convective turbulent dust emission (CTDE) are presented. The scheme is advanced by including (1) a new statistical description of instantaneous momentum flux, (2) a correction function for cohesive force to account for the effect of soil moisture, and (3) a correction function for lifting force to consider the effect of vegetation roughness elements. The probability density function describing instantaneous momentum flux is now derived from large-eddy simulations for different atmospheric stabilities. The vegetation correction function is based on a drag partition theory. Additional improvements on the representations of interparticle cohesive force and particle size distribution are introduced. The new CTDE scheme is tested against the field data obtained at a sand storm monitoring station in the Horqin Sandy Land in China in 2011 and during the Japan-Australia Dust Experiment in Australia in 2006.

Abstract. We develop a parameterization scheme of convective dust emission for regional and global atmospheric models. Convective dust emission occurs in the absence of saltation as large eddies intermittently produce strong shear stresses on the surface and entrain dust particles into the air. This dust emission mechanism has not been included in the traditional dust models. The scheme presented in this study is a new approach which takes account of the stochastic nature of convective dust emission. It consists of the statistical representations of soil particle size, inter-particle cohesion, and instantaneous surface shear stress. A method of determining the probability density function of the latter quantity is proposed. Dust emission is then estimated from the overlap of the probability density functions of the aerodynamic lifting and inter-particle cohesive forces. The new scheme is implemented into the WRF/Chem model and applied to dust modeling in the Taklimakan Desert. A comparison with lidar data shows that the model can reproduce the main features of the dust patterns and their diurnal variations. For the case studied, convective dust emission is typically several µg m −2 s −1 and at times up to 50 µg m −2 s −1 .

20Particle lifting in dust devils on both Earth and Mars has been studied from many different 21 perspectives, including how dust devils could influence the dust cycles of both planets. Here we review 22 our current understanding of particle entrainment by dust devils by examining results from field 23 observations on Earth and Mars, laboratory experiments (at terrestrial ambient and Mars-analog 24 conditions), and analytical modeling. By combining insights obtained from these three methodologies, 25we provide a detailed overview on interactions between particle lifting processes due to mechanical, 26 thermal, electrodynamical and pressure effects, and how these processes apply to dust devils on