Dust Emission Flux Research Articles

Increasing Arctic dust suppresses the reduction of ice nucleation in the Arctic lower troposphere by warming

Ice nucleating particles (INPs) affect the cloud radiative budget in the rapidly warming Arctic by changing the cloud liquid/ice phase balance. Dust emitted in the Arctic (Arctic dust) has been suggested to be a major contributor to INPs in the Arctic lower troposphere. However, how Arctic dust and its impacts on ice nucleation change with Arctic warming has not been explored. Here we find that the simulated dust emission flux in the Arctic (>60°N) in global model simulations increases by 20% from 1981–1990 to 2011–2020. This increase weakens the sensitivity of ice nucleation in Arctic lower tropospheric clouds to warming by 40% compared to the case without considering Arctic dust emission increases. Our results demonstrate a better understanding of the counterbalancing feedbacks of Arctic dust (i.e., increasing emissions and decreasing ice nucleation efficiency) is needed for more accurate estimates of changes in ice nucleation in the rapidly changing Arctic climate.

Source contributions to two super dust storms over Northern China in March 2021 and the impact of soil moisture

Two extremely devastating super dust storms (SDS) hit Mongolia and Northern China in March 2021, causing many deaths and substantial economic damage. Accurate forecasting of dust storms is of great importance for avoiding or mitigating their effects. One of the most critical factors affecting dust emissions is soil moisture, but its value in desert exhibits significant uncertainty. In this study, model experiments were conducted to simulate dust emissions using four soil moisture datasets. The results were compared with observations to assess the effects of soil moisture on the dust emission strength. The Integrated Source Apportionment Method (ISAM) was used to track the dust sources and quantify the contribution from each source region to the dust load over the North China Plain (NCP), Korea peninsula, and western Japan. The results show large differences in the dust load depending on the soil moisture datasets used. The high soil moisture in the NCEP dataset results in substantial underestimation of the dust emission flux and PM10 concentration. Despite a minor overestimation of PM10 concentrations in many Northern China cities, the ERA5 dataset yields the best simulation performance. During the two SDS events, about 7.5 Mt dust was released from the deserts in Mongolia and 2.8 Mt from the deserts in China. Source apportionment indicates that the Mongolian Gobi Desert is the dominant source of PM10 in the NCP, Korea peninsula, and western Japan, accounting for 60 %–80 %, while Inner Mongolia contributed 10 %–20 %.

Long-range transport impact of a severe dust storm over the Yangtze River Basin region and its modeling sensitivity to dust emission scheme

Dust storms frequently occur in the spring over East Asia, affecting southern Mongolia and northeast China. An exceptionally powerful dust storm occurred in East Asia from March 14th to March 18th, 2021. To investigate the ability of climate models to simulate severe dust storms, we employed the Weather Research Forecast model coupled with chemistry (WRF-Chem) with Goddard Chemistry Aerosol Radiation and Transport (GOCART), SHAO and KOK dust emission schemes to simulate the evolution of this event and to characterize dust aerosols long-range transport. Results showed that this storm was caused by a Mongolian cyclone depicted at 850 hPa with a cold front, which swept dust aerosols southeastward across southern Mongolia to northeast China. Model evaluation with satellite-retrieved Aerosol Optical Depth (AOD) and observational PM10 concentrations revealed that the SHAO dust emission scheme performed better in simulating spatial and temporal distribution of AOD over the Gobi Desert (GD) but overestimated them over Taklimakan Desert (TD). In contrast, the GOCART dust emission scheme underestimated AOD over most areas except the Taklimakan Desert; the KOK dust emission scheme overestimated them over both TD and GD. Overall, the SHAO dust emission scheme had good performance in simulating the surface PM10 concentrations over the Yangtze River Basin (YRB) and depicted an increase in PM10 concentrations, which denoted the transport of dust aerosols over YRB. As a better description of the physical process of dust emission flux over the eastern region of the Gobi Desert, the SHAO dust emission scheme depicted well the spatial and temporal evolution of dust plume episodes, especially over northeast China and YRB. The significant differences in dust emission fluxes between the three dust emission schemes were attributed to the sensitivity of threshold friction velocity and erodibility factor. Thereunto, the SHAO dust emission scheme incorporated well soil particle size distribution and threshold velocity to produce the dust emission flux, which allowed higher dust emission flux over the eastern GD and under strong southwesterly transported dust aerosols to East Central China's region of North China Plain (NCP) and YRB. This study will help further the simulation of extreme dust events more accurately and the exploration of climate change's effect on dust events over East Asia.

Wind tunnel simulation of wind erosion and dust emission processes, and the influences of soil texture

Dust emission caused by wind erosion of soil is an important surface process in arid and semi-arid regions. However, existing dust emission models pay insufficient attention to the impacts of aerodynamic entrainment of particles. In addition, studies of wind erosion processes do not adequately account for the dynamics of wind erosion rates and dust emission fluxes, or for the impact of soil texture on dust emission. Our wind tunnel simulations of wind erosion and dust emission showed that the soil texture, wind erosion duration, and shear velocity are major factors that affect the dynamics of wind erosion and dust emission. Because of the limited supply of surface sand and the change in surface erosion resistance caused by surface coarsening during erosion, the wind erosion rate and the flux of particles smaller than 10 μm (PM10) caused by aerodynamic entrainment decreased rapidly with increasing erosion duration, which suggests that surface wind erosion and dust emission occur primarily during the initial stage of wind erosion. The PM10 emission efficiency decreased with increasing shear velocity following a power function, and finer textured sandy loam soils had greater PM10 emission efficiency than loamy sand soils.

A new process-based and scale-aware desert dust emission scheme for global climate models – Part I: Description and evaluation against inverse modeling emissions

Abstract. Desert dust accounts for most of the atmosphere's aerosol burden by mass and produces numerous important impacts on the Earth system. However, current global climate models (GCMs) and land-surface models (LSMs) struggle to accurately represent key dust emission processes, in part because of inadequate representations of soil particle sizes that affect the dust emission threshold, surface roughness elements that absorb wind momentum, and boundary-layer characteristics that control wind fluctuations. Furthermore, because dust emission is driven by small-scale (∼ 1 km or smaller) processes, simulating the global cycle of desert dust in GCMs with coarse horizontal resolutions (∼ 100 km) presents a fundamental challenge. This representation problem is exacerbated by dust emission fluxes scaling nonlinearly with wind speed above a threshold wind speed that is sensitive to land-surface characteristics. Here, we address these fundamental problems underlying the simulation of dust emissions in GCMs and LSMs by developing improved descriptions of (1) the effect of soil texture on the dust emission threshold, (2) the effects of nonerodible roughness elements (both rocks and green vegetation) on the surface wind stress, and (3) the effects of boundary-layer turbulence on driving intermittent dust emissions. We then use the resulting revised dust emission parameterization to simulate global dust emissions in a standalone model forced by reanalysis meteorology and land-surface fields. We further propose (4) a simple methodology to rescale lower-resolution dust emission simulations to match the spatial variability of higher-resolution emission simulations in GCMs. The resulting dust emission simulation shows substantially improved agreement against regional dust emissions observationally constrained by inverse modeling. We thus find that our revised dust emission parameterization can substantially improve dust emission simulations in GCMs and LSMs.

Modeling atmospheric microplastic cycle by GEOS-Chem: An optimized estimation by a global dataset suggests likely 50 times lower ocean emissions

Modeling atmospheric microplastic cycle by GEOS-Chem: An optimized estimation by a global dataset suggests likely 50 times lower ocean emissions

Application of a satellite-retrieved sheltering parameterization (v1.0) for dust event simulation with WRF-Chem v4.1

Abstract. Roughness features (e.g., rocks, vegetation, furrows) that shelter or attenuate wind flow over the soil surface can considerably affect the magnitude and spatial distribution of sediment transport in active aeolian environments. Existing dust and sediment transport models often rely on vegetation attributes derived from static land use datasets or remotely sensed greenness indicators to incorporate sheltering effects on simulated particle mobilization. However, these overly simplistic approaches do not represent the three-dimensional nature or spatiotemporal changes of roughness element sheltering. They also ignore the sheltering contribution of non-vegetation roughness features and photosynthetically inactive (i.e., brown) vegetation common to dryland environments. Here, we explore the use of a novel albedo-based sheltering parameterization in a dust transport modeling application of the Weather Research and Forecasting model with Chemistry (WRF-Chem). The albedo method estimates sheltering effects on surface wind friction speeds and dust entrainment from the shadows cast by subgrid-scale roughness elements. For this study, we applied the albedo-derived drag partition to the Air Force Weather Agency (AFWA) dust emission module and conducted a sensitivity study on simulated PM10 concentrations using the Georgia Institute of Technology–Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model as implemented in WRF-Chem v4.1. Our analysis focused on a convective dust event case study from 3–4 July 2014 for the southwestern United States desert region discussed by other published works. Previous studies have found that WRF-Chem simulations grossly overestimated the dust transport associated with this event. Our results show that removing the default erodibility map and adding the drag parameterization to the AFWA dust module markedly improved the overall magnitude and spatial pattern of simulated dust conditions for this event. Simulated PM10 values near the leading edge of the storm substantially decreased in magnitude (e.g., maximum PM10 values were reduced from 17 151 to 8539 µg m−3), bringing the simulated results into alignment with the observed PM10 measurements. Furthermore, the addition of the drag partition restricted the erroneous widespread dust emission of the original model configuration. We also show that similar model improvements can be achieved by replacing the wind friction speed parameter in the original dust emission module with globally scaled surface wind speeds, suggesting that a well-tuned constant could be used as a substitute for the albedo-based product for short-duration simulations in which surface roughness is not expected to change and for landscapes wherein roughness is constant over years to months. Though this alternative scaling method requires less processing, knowing how to best tune the model winds a priori could be a considerable challenge. Overall, our results demonstrate how dust transport simulation and forecasting with the AFWA dust module can be improved in vegetated drylands by calculating the dust emission flux with surface wind friction speed from a drag partition treatment.

On the Influence of Thermal Stratification on Emitted Dust Flux

AbstractThe influence of the atmospheric boundary layer (ABL) stability on dust emitted from saltation is usually neglected. This has been challenged by two recent studies which suggested a dependency of the dust emission flux particle size distribution (PSD) to the thermal stratification. Both studies observed a dust flux enrichment in fine particles with instability but for two different explanations: (a) a larger eddy diffusivity of submicron particles with instability, and (b) an enhanced turbulence and friction velocity u* stochasticity with instability, increasing saltation bombardment and fine‐dust emission. Here, we discuss and investigate these two propositions using the WIND‐O‐V (WIND erOsion in presence of sparse Vegetation's) 2017 data set. We first show that the first explanation and the observed stability effect on the dust flux are questionable. We, then, investigate the second explanation in the context of the enhanced influence of ABL‐scale motions on the near‐surface turbulence and u* stochasticity with increasing instability. This second explanation appears only possible at the transition between windy and free convection regimes where u* is close to its erosion threshold value. However, this intermediate regime appears more convective than the erosion event from whom the second explanation was proposed. Overall, our results show no thermal stability effect on the dust emission flux PSD. Instead, u* and the air relative humidity seem to be the main meteorological variables influencing the dust emission flux PSD. We, in particular, suggest that the air relative humidity may have affected the surface soil moisture, and thus the interparticle cohesion, through water vapor adsorption.

Emission, transport, deposition, chemical and radiative impacts of mineral dust during severe dust storm periods in March 2021 over East Asia

A Regional Air Quality Model System (named RAQMS) coupled with a developed dust model driven by WRF was applied to synthetically investigate the emission, transport, deposition, budget, and chemical and radiative effects of mineral dust during the severe dust storm periods of 10–31 March 2021. Model results were validated against a variety of ground, vertical and satellite observations, which demonstrated a generally good model ability in reproducing meteorological variables, particulate matter and compositions, and aerosol optical properties. The first dust storm (DS1), which was the severest one since 2010 was originated from the Gobi Desert in southern Mongolia on 14 March, with the dust emission flux reaching 2785 μg m−2 s−1 and the maximum dust concentration exceeding 18,000 μg m−3 in the dust deflation region. This dust storm resulted in remarkably high hourly PM10 observations up to 7506 μg m−3, 1887 μg m−3, and 2704 μg m−3 in Beijing, Tianjin, and Shijiazhuang on 15 March, respectively, and led to a maximum decrease in surface shortwave radiation up to 313.4 W m−2 (72 %) in Beijing. The second dust storm (DS2) broke out in the deserts of eastern Mongolia, with lower dust emission than the first one. The extinction of shortwave radiation by dust aerosols led to a reduction in photolysis rate and consequently decreases in O3 and secondary aerosol concentrations over the North China Plain (NCP), whereas total sulfate and nitrate concentrations consistently increased due to heterogeneous reactions on dust surfaces over the middle reaches of the Yellow River and the NCP region during DS1. Sulfate and nitrate formation through heterogeneous reactions were enhanced in the dust backflow on 16–17 March by approximately 18 % and 24 % on average in the NCP. Heterogeneous reactions and photolysis rate reduction by mineral dust jointly led to average changes in sulfate, nitrate, ammonium, and secondary organic aerosol (SOA) concentrations by 13.0 %, 13.5 %, −12.3 %, and −4.4 %, respectively, in the NCP region during DS1, larger than the changes in the Yangtze River Delta (YRD). The maximum dry deposition settled in the 7–11 μm size range in downwind land and ocean areas, while wet deposition peaked in the 4.7–7 μm size range in the entire domain. Wet deposition was approximately twice the dry deposition over mainland China except for dust source regions. During 10–31 March, the total dust emission, dry and wet depositions were estimated to be 31.4 Tg, 13.78 Tg and 4.75 Tg, respectively, with remaining 12.87 Tg of dust aerosols (41 % of the dust emission) suspending in the atmosphere or transporting to other continents and oceans.

Unraveling the Roles of Saltation Bombardment and Atmospheric Instability on Magnitude and Size Distribution of Dust Emission Fluxes: Lessons From the JADE and WIND‐O‐V Experiments

AbstractThe size distribution of the vertical flux of dust freshly emitted from a wind‐eroded surface was recently shown to depend on the thermal stratification of the surface boundary layer (SBL). These new results question the way dust emission is currently represented in the dust models and emphasize the need to identify the factors controlling the intensity and size‐resolved dust flux at emission. In this study, we re‐analyze the data of two major campaigns (JADE and WIND‐O‐V) performed on unvegetated plots and during which the characteristics of the (a) surface of the eroding fields, (b) aerodynamic conditions (wind speed, stability of the SBL), (c) saltation flux (intensity and size distribution), and (d) vertical dust flux (intensity and size distribution) determined by the gradient method were carefully documented. The magnitude and size distribution of the vertical dust flux are found to be deeply intertwined and to be controlled in the first place by the kinetic energy of the saltating sand grains, and to a lesser extent by the size‐dependent uplift of the sandblasted particles. In unstable conditions coarser sand grains are mobilized, which increases the kinetic energy of the saltation flux and leads to the production of finer particles by sandblasting. Conversely, the uplift of supermicron particles is facilitated by the increase of the wind friction velocity, which results in an enrichment of the vertical dust flux in the coarsest particles at large wind speeds. The implications of these new findings are particularly important for the modeling of the dust emission/transport/deposition cycle.

Deciphering the Role of Aerosol‐Induced Snow Albedo Feedback on Dust Emission Over the Tibetan Plateau

AbstractThe aerosol‐induced snow albedo effect (SAE) and its feedback on the dust emission over the Tibetan Plateau are investigated using the regional climate model (RegCM4.6) coupled with the SNow, ICe, and Aerosol Radiative model. The deposition of absorbing aerosols (black carbon and dust) decreases the albedo of snow over the Himalayan‐Tibetan region, which results in significant surface warming of 1–4 K. This aerosol‐induced surface warming and accelerated snow melting decreased fractional snow cover by 8% and number of snow cover days by 20 days over the region. Compared to the control simulation, this early and more exposure of nonvegetated land resulted in the increase of the dust emission flux by 60% over central Tibet and therefore the columnar dust loading by 10%–40%. This effect alone results in a surface cooling of −4 Wm−2 and also increases the occurrence of dust events by 10%–20%. Therefore, the snow darkening effect due to the deposition of black carbon and dust increases the local emission of dust aerosols, which further increases the aerosol‐induced snow melting and thus perturbs the air quality and radiation balance over the high mountains of Asia.

Antecedent Soil Moisture Conditions Influenced Vertical Dust Flux: A Case Study in Iran Using WRF-Chem Model

Soil moisture is one of the most important parameters affecting dust emission flux. This study was conducted to investigate the effects of soil moisture on vertical dust flux in the central plateau region of Iran. In this study, the WRF-Chem (Weather Research and Forecast with Chemistry) model, with the GOCART (Global Ozone Chemistry Aerosol Radiation and Transport) scheme, was used to estimate the dust emission flux during a major storm from 19 to 21 July 2015, and to discriminate between dust sources. The results showed that the Kyrgyz deserts in Turkmenistan, the Arabian deserts in Saudi Arabia, the deserts of Iraq, and the Helmand region in Afghanistan are sources of foreign dust. Additionally, the central desert plain was identified as an internal dust source, where the dust level reached 7000 µg m−2 s−1. The results of WRF-Chem simulation were verified with reanalysis data from MERRA2 and AERONET data from Natanz station, which showed good agreement with the simulation. Based on the GLDAS reanalysis, soil moisture content varied between 2.6% and 34%. Linear and nonlinear regression of vertical dust flux values and soil moisture showed nonlinear behavior following the exponential function, with a correlation coefficient of 0.8 and a strong negative association between soil moisture and vertical dust flux.

Estimating the sand saltation thresholds from Sentinel-1 SAR data in the Gobi Desert, Mongolia

Spatial information about the sand saltation threshold is essential to quantify sand transport and dust emission. Quantitatively estimating the threshold over a wide area is challenging, however, because its main influencing factors (surface roughness elements) are unknown. Here, we explored the use of Sentinel-1 Synthetic Aperture Radar (SAR) data to quantify surface roughness conditions and their temporal changes and map the threshold. Thresholds were obtained by in situ observations in dry spring periods during 2018–2020 at three year-round and eight temporary sites during natural sand and dust storms. We found a linear relationship (r = 0.91, p < 0.0001) between the SAR gamma naught VV intensity and the observed threshold where the site surface was stony or vegetated, indicating that SAR data can be used to quantify the spatial-temporal distribution of the threshold during dry periods. We then estimated thresholds from SAR data for spring 2017–2021 and found high thresholds on slopes and mountains, mainly due to stone and vegetation effects, whereas thresholds in the topographic depression varied because of changes in surface roughness conditions. Thresholds estimated from SAR data should greatly improve wide-area simulations of sand horizontal transport and dust emission fluxes by numerical dust models.

Dynamic processes of dust emission from gobi: A portable wind tunnel study atop the Mogao Grottoes, Dunhuang, China

The dynamic process of dust emission from gobi is a largely un-solved scientific question while it is essential for minimizing the dust hazards. In this study, field wind tunnel experiments have been performed to reveal the processes of dust emission from gobi on the top of the Mogao Grottoes. We found that the dust content of gobi is the dominant factor that determines the intensity of dust emission. The vertical PM10 flux increased exponentially with the increase of dust content on the gobi surface at a given wind speed. The impact energy of saltating particles is another control factor of the dust emission flux. The vertical PM10 flux due to saltation bombardment of the external sand supply was 5–13 times larger than that without the bombardment of sand supply. This study indicates that gobi on the top of the Mogao Grottoes is one of the main dust sources as it has an abundance of sand supply from Mingsha Mountain as well as its richness in dust content. Hence, it is imperative to expand the existing sand control system on the top of the Mogao Grottoes in order to minimize the impact of dust hazards on the Mogao Grottoes.

Study on dust occurrence and transportation related to boundary layer height in Northwest China

AbstractBoundary layer development has a significant influence on dust emission and transportation. The effects of surface heat flux on distribution of dust related to BLH (boundary layer height) during a dust event in Northwest China are discussed by numerical simulation. The results show that: the dust emissions start in Dunhuang and strengthen in Minqin with large dust emission fluxes (as high as 3000 μg m−2 s−1) and surface wind speed (up to 20 m s−1). The dust at the early stage mainly concentrates below 500 m above the ground, then lifts over 3000 m above the ground at the strengthening stage, and the concentration in high value center is more than 24,000 μg m−3 at the dust source Dunhuang. The high dust concentration in Minqin maintains at about 1000 m above the ground. Weak dust emission in Minqin makes the dust concentration near the ground less than that in the upper air. The BLH in the high dust concentration center is higher than that in the surrounding area at the emission stage in Dunhuang. Sensitivity experiment with turning off surface heat flux shows obvious decrease of the dust concentration in Dunhuang, with more than four times reduction of the surface dust concentration. The BLH near the high dust concentration area reduces significantly in the sensitivity experiment. However, the gap between the two experiments reduces with the dust development. The BLH in the sensitivity experiment has small spatial differences with uniform distribution in Dunhuang. It means that the thermodynamic contribution is main reason for the distribution differences. The two experiments in Minqin also show that the height of high concentration dust has a difference of about 500 m. The dust lifts with the boundary layer development, but shows different distribution characteristics and influencing factors between Dunhuang and Minqin.

Dynamic Dust Source Regions and the Associated Natural and Anthropogenic Dust Emissions at the Global Scale

Dust emission is a key factor for reproducing dust’s physical process and its climate impact in dust modeling. However, previous studies always employed static land cover types to classify potential dust sources, ignoring dynamic variations in the surface bareness, which may lead to large uncertainties in the simulated dust emission fluxes, especially in regard to anthropogenic dust (AD) emission induced by wind erosion of human-disturbed land surfaces. Combined with anthropogenic land use and land cover change, dynamic dust source regions and the associated natural dust (ND) and AD emissions at the global scale from 2001 to 2018 are estimated in this study. The results show that the AD emissions exhibit a significant seasonal variability and dispersion at the global scale in contrast to the generally concentrated spatial distributions of ND emissions. The high-value ND areas are primarily located in the Sahara Desert, Arabian Peninsula, Karakum Desert, East Asia, Australian Desert, and other large desert areas, and the ND emission flux reaches a maximum of 50 μg m−2 s−1 or higher. High values of the annual average AD emission fluxes are located in southern Russia (124.6 ± 26.6 μg m−2 s−1), northern China (103.2 ± 21.9 μg m−2 s-1), the central and northern United States (56.0 ± 17.4 μg m−2 s−1), and the southern side of the Sahara Desert (74.1 ± 14.2 μg m−2 s−1). Especially in southern Russia and northern Kazakhstan, the AD emission flux accounts for the largest contribution to the total dust emission flux, at 98.2%. The ND emission flux demonstrates an upward trend in the central Sahara Desert, southern Arabian Desert, and Iranian regions and a significant downward trend in northwestern China. The AD emissions exhibit a decreasing trend in northern China, western India, the southern side of the Sahara Desert, and the central United States from 2001 to 2018 due to the implementation of environmental protection policies and a decrease in the wind speed, with the highest rate of decline reaching −74.9 μg m−2 s−1/decade. This study provided confidence for the further investigation of dust mass balance and the climatic impacts of natural and anthropogenic dust.

Simulation of a Severe Sand and Dust Storm Event in March 2021 in Northern China: Dust Emission Schemes Comparison and the Role of Gusty Wind

Northern China experienced a severe sand and dust storm (SDS) on 14/15 March 2021. It was difficult to simulate this severe SDS event accurately. This study compared the performances of three dust-emission schemes on simulating PM10 concentration during this SDS event by implementing three vertical dust flux parameterizations in the Comprehensive Air-Quality Model with Extensions (CAMx) model. Additionally, a statistical gusty-wind model was implemented in the dust-emission scheme, and it was used to quantify the gusty-wind contribution to dust emissions and peak PM10 concentration. As a result, the LS scheme (Lu and Shao 1999) produced the minimum errors for peak PM10 concentrations, the MB scheme (Marticorena and Bergametti 1995) underestimated the PM10 concentrations by 70–90%, and the KOK scheme (Kok et al. 2014) overestimated PM10 concentrations by 10–50% in most areas. The gusty-wind model could reasonably reproduce the probability density function of 2-min wind speeds. There were 5–40% more dust-emission flux and 5–40% more peak PM10 concentrations generated by the gusty wind than the hourly wind in the dust-source regions. The increase of peak PM10 concentration caused by gusty wind in the non-dust-source regions was higher than in the dust-source regions, with 10–50%. Implementing the gusty-wind model could help improve the LS scheme’s performance in simulating PM10 concentrations of this severe SDS event. More work is still needed to investigate the reliability of the gusty-wind model and LS scheme on various SDS events.

Contemporary and future dust sources and emission fluxes from gypsum- and quartz-dominated eolian systems, New Mexico and Texas, USA

AbstractRecent research on dust emissions from eolian dunes seeks to improve regional and global emissions estimates and knowledge of dust sources, particularly with a changing climate. Dust emissions from dune fields can be more accurately estimated when considering the whole eolian system composed of active to stabilized dunes, interdunes, sand sheets, and playas. Each landform can emit different concentrations of dust depending on the supply of silt and clay, soil surface characteristics, and the degree to which the landforms are dynamic and interact. We used the Portable In Situ Wind Erosion Laboratory (PI-SWERL) to measure PM10 (particulate matter &amp;lt;10 μm) dust emission potential from landforms in two end-member eolian systems: the White Sands dune field in New Mexico (USA), composed of gypsum, and the Monahans dune field in west Texas, composed of quartz. White Sands is a hotspot of dust emissions where dunes and the adjacent playa yield high dust fluxes up to 8.3 mg/m2/s. In contrast, the active Monahans dunes contain 100% sand and produce low dust fluxes up to 0.5 mg/m2/s, whereas adjacent stabilized sand sheets and dunes that contain silt and clay could produce up to 17.7 mg/m2/s if reactivated by climate change or anthropogenic disturbance. These findings have implications for present and future dust emission potential of eolian systems from the Great Plains to the southwestern United States, with unrealized emissions of &amp;gt;300 t/km2/yr.

Mineral dust cycle in the Multiscale Online Nonhydrostatic AtmospheRe CHemistry model (MONARCH) Version 2.0

Abstract. We present the dust module in the Multiscale Online Non-hydrostatic AtmospheRe CHemistry model (MONARCH) version 2.0, a chemical weather prediction system that can be used for regional and global modeling at a range of resolutions. The representations of dust processes in MONARCH were upgraded with a focus on dust emission (emission parameterizations, entrainment thresholds, considerations of soil moisture and surface cover), lower boundary conditions (roughness, potential dust sources), and dust–radiation interactions. MONARCH now allows modeling of global and regional mineral dust cycles using fundamentally different paradigms, ranging from strongly simplified to physics-based parameterizations. We present a detailed description of these updates along with four global benchmark simulations, which use conceptually different dust emission parameterizations, and we evaluate the simulations against observations of dust optical depth. We determine key dust parameters, such as global annual emission/deposition flux, dust loading, dust optical depth, mass-extinction efficiency, single-scattering albedo, and direct radiative effects. For dust-particle diameters up to 20 µm, the total annual dust emission and deposition fluxes obtained with our four experiments range between about 3500 and 6000 Tg, which largely depend upon differences in the emitted size distribution. Considering ellipsoidal particle shapes and dust refractive indices that account for size-resolved mineralogy, we estimate the global total (longwave and shortwave) dust direct radiative effect (DRE) at the surface to range between about −0.90 and −0.63 W m−2 and at the top of the atmosphere between −0.20 and −0.28 W m−2. Our evaluation demonstrates that MONARCH is able to reproduce key features of the spatiotemporal variability of the global dust cycle with important and insightful differences between the different configurations.

The Dust Emission Potential of Agricultural‐Like Fires—Theoretical Estimates From Two Conceptually Different Dust Emission Parameterizations

AbstractAgricultural fires affecting grass‐, crop‐ and shrublands represent a major, mainly anthropogenically driven disturbance of many ecosystems. In addition to emissions of carbonaceous aerosol, they were found to inject also mineral dust particles into the atmosphere. The fires can significantly modulate the near‐surface wind patterns so that conditions suitable for dust emission occur. However, the exact emission mechanism has not been investigated so far, but is inevitable for the understanding of its impacts on the Earth system. Here, we test two dust emission parameterizations representing saltation bombardment (SALT) and direct aerodynamic dust entrainment by (convective) turbulence (convective turbulent dust emission, CTDE) in the context of fire‐modulated wind patterns using large‐eddy simulation with an idealized setup to represent typical agricultural fire settings. Favorable aerodynamic preconditions for the initialization of both emission processes are found, however, with sometimes significant differences in dust emission flux depending on specific wind and fire properties. The strong fire‐induced modulations of the instantaneous momentum flux suggest that CTDE can be a very potent emission process in the fire vicinity. Nevertheless, fire impacts on the friction velocity can be significant too, so that dust emission through SALT is facilitated as well. Ultimately, the specific aerodynamic conditions within pyro‐convectively modulated wind patterns require the development of a parameterization that can describe these unique fire‐related dust emissions and their influencing factors properly. This will finally allow for considering fire‐induced dust emissions in aerosol‐atmosphere models and an investigation of its atmospheric impacts such as on the radiation budget.