scholarly journals Identification of Dust Sources in a Saharan Dust Hot-Spot and Their Implementation in a Dust-Emission Model

2018 ◽  
Vol 11 (1) ◽  
pp. 4 ◽  
Author(s):  
Stefanie Feuerstein ◽  
Kerstin Schepanski
Keyword(s):  
Mineral Dust ◽  
Dust Emission ◽  
Sediment Supply ◽  
Emission Model ◽  
Atmospheric Dust ◽  
Dust Source ◽  
Dust Sources ◽  
Dust Load ◽  
Supply Information ◽  
Sentinel 2

Although mineral dust plays a key role in the Earth’s climate system and in climate and weather prediction, models still have difficulties in predicting the amount and distribution of mineral dust in the atmosphere. One reason for this is the limited understanding of the distribution of dust sources and their behavior with respect to their spatiotemporal variability in activity. For a better estimation of the atmospheric dust load, this paper presents an approach to localize dust sources and thereby estimate the sediment supply for a study area centered on the Aïr Massif in Niger with a north–south extent of 16 ∘ –22 ∘ N and an east–west extent of 4 ∘ –12 ∘ E. This approach uses optical Sentinel-2 data at visible and near infrared wavelengths together with HydroSHEDS flow accumulation data to localize ephemeral riverbeds. Visible channels from Sentinel-2 data are used to detect sand sheets and dunes. The identified sediment supply map was compared to the dust source activation frequency derived from the analysis of Desert-Dust-RGB imagery from the Meteosat Second Generation series of satellites. This comparison reveals the strong connection between dust activity, prevailing meteorology and sediment supply. In a second step, the sediment supply information was implemented in a dust-emission model. The simulated emission flux shows how much the model results benefit from the updated sediment supply information in localizing the main dust sources and in retrieving the seasonality of dust activity from these sources. The described approach to characterize dust sources can be implemented in other regional model studies, or even globally, and can thereby help to get a more accurate picture of dust source distribution and a more realistic estimation of the atmospheric dust load.

scholarly journals Evaluating dust emission model performance using dichotomous satellite observations of dust emission

2022 ◽  
Author(s):  
Mark Hennen ◽  
Adrian Chappell ◽  
Nicholas Webb ◽  
Kerstin Schepanski ◽  
Matthew Baddock ◽  
...  
Keyword(s):  
Wind Speed ◽  
Dust Emission ◽  
Point Sources ◽  
Sediment Supply ◽  
Emission Model ◽  
Atmospheric Dust ◽  
Wind Speeds ◽  
Space And Time ◽  
The Us ◽  
Emission Models

Abstract. Measurements of dust in the atmosphere have long been used to calibrate dust emission models. However, there is growing recognition that atmospheric dust confounds the magnitude and frequency of emission from dust sources and hides potential weaknesses in dust emission model formulation. In the satellite era, dichotomous (presence = 1 or absence = 0) observations of dust emission point sources (DPS) provide a valuable inventory of regional dust emission. We used these DPS data to develop an open and transparent framework to routinely evaluate dust emission model (development) performance using coincidence of simulated and observed dust emission (or lack of emission). To illustrate the utility of this framework, we evaluated the recently developed albedo-based dust emission model (AEM) which included the traditional entrainment threshold (u*ts) at the grain scale, fixed over space and static over time, with sediment supply infinite everywhere. For comparison with the dichotomous DPS data, we reduced the AEM simulations to its frequency of occurrence in which soil surface wind friction velocity (us*) exceeds the u*ts, P(us* > u*ts). We used a global collation of nine DPS datasets from established studies to describe the spatio-temporal variation of dust emission frequency. A total of 37,352 unique DPS locations were aggregated into 1,945 1° grid boxes to harmonise data across the studies which identified a total of 59,688 dust emissions. The DPS data alone revealed that dust emission does not usually recur at the same location, are rare (1.8 %) even in North Africa and the Middle East, indicative of extreme, large wind speed events. The AEM over-estimated the occurrence of dust emission by between 1 and 2 orders of magnitude. More diagnostically, the AEM simulations coincided with dichotomous observations ~71 % of the time but simulated dust emission ~27 % of the time when no dust emission was observed. Our analysis indicates that u*ts was typically too small, needed to vary over space and time, and at the grain-scale u*ts is incompatible with the us* scale (MODIS 500 m). During observed dust emission, us* was too small because wind speeds were too small and/or the wind speed scale (ERA5; 11 km) is incompatible with the us* scale. The absence of any limit to sediment supply caused the AEM to simulate dust emission whenever P (us* > u*ts), producing many false positives when and where wind speeds were frequently large. Dust emission model scaling needs to be reconciled and new parameterisations are required for u*ts and to restrict sediment supply varying over space and time. Whilst u*ts remains poorly constrained and unrealistic assumptions persist about sediment supply and availability, the DPS data provide a basis for the calibration of dust emission models for operational use. As dust emission models develop, these DPS data provide a consistent, reproducible, and valid framework for their routine evaluation and potential model optimisation. This work emphasises the growing recognition that dust emission models should not be evaluated against atmospheric dust.

scholarly journals New developments in the representation of Saharan dust sources in the aerosol–climate model ECHAM6-HAM2

2016 ◽  
Vol 9 (2) ◽  
pp. 765-777 ◽  
Author(s):  
Bernd Heinold ◽  
Ina Tegen ◽  
Kerstin Schepanski ◽  
Jamie R. Banks
Keyword(s):  
Climate Model ◽  
Dust Emission ◽  
Source Area ◽  
Saharan Dust ◽  
Moist Convection ◽  
Dust Source ◽  
New Developments ◽  
Infrared Imager ◽  
Dust Sources ◽  
Dust Events

Abstract. In the aerosol–climate model ECHAM6-HAM2, dust source activation (DSA) observations from Meteosat Second Generation (MSG) satellite are proposed to replace the original source area parameterization over the Sahara Desert. The new setup is tested in nudged simulations for the period 2007 to 2008. The evaluation is based on comparisons to dust emission events inferred from MSG dust index imagery, Aerosol Robotic Network (AERONET) sun photometer observations, and satellite retrievals of aerosol optical thickness (AOT).The model results agree well with AERONET measurements especially in terms of seasonal variability, and a good spatial correlation was found between model results and MSG-SEVIRI (Spinning-Enhanced Visible and InfraRed Imager) dust AOT as well as Multi-angle Imaging SpectroRadiometer (MISR) AOT. ECHAM6-HAM2 computes a more realistic geographical distribution and up to 20 % higher annual Saharan dust emissions, using the MSG-based source map. The representation of dust AOT is partly improved in the southern Sahara and Sahel. In addition, the spatial variability is increased towards a better agreement with observations depending on the season. Thus, using the MSG DSA map can help to circumvent the issue of uncertain soil input parameters.An important issue remains the need to improve the model representation of moist convection and stable nighttime conditions. Compared to sub-daily DSA information from MSG-SEVIRI and results from a regional model, ECHAM6-HAM2 notably underestimates the important fraction of morning dust events by the breakdown of the nocturnal low-level jet, while a major contribution is from afternoon-to-evening emissions.

scholarly journals North African dust transport toward the western Mediterranean basin: Atmospheric controls on dust source activation and transport pathways during June–July 2013

2016 ◽  
Author(s):  
Kerstin Schepanski ◽  
Marc Mallet ◽  
Bernd Heinold ◽  
Max Ulrich
Keyword(s):  
Atmospheric Circulation ◽  
Mediterranean Basin ◽  
Dust Emission ◽  
Western Mediterranean ◽  
North African ◽  
Atmospheric Dust ◽  
Dust Source ◽  
Dust Transport ◽  
The Mediterranean ◽  
Heat Low

Abstract. Dust transported from North African source region toward the Mediterranean basin and Europe is an ubiquitous phenomenon in the Mediterranean region. Winds formed by large-scale pressure gradients foster dust entrainment into the atmosphere over North African dust source regions and advection of dust downwind. The constellation of centers of high and low pressure determines wind speed and direction, and thus the chance for dust emission over Northern Africa and transport toward the Mediterranean. Here, we present characteristics of the atmospheric dust life-cycle determining dust transport toward the Mediterranean basin. Using the atmosphere-dust model COSMO-MUSCAT (COSMO: COnsortium for Small-scale MOdelling; MUSCAT: MUltiScale Chemistry Aerosol Transport Model), a complementary analysis of dust source activation, emission fluxes, transport pathways, and deposition rates is provided with focus on the ChArMEx (Chemistry-Aerosol Mediterranean Experiment) special observation period in June and July 2013. Modes of atmospheric circulation, identified from empirical orthogonal function (EOF) analysis of the geopotential height at 850 hPa are used for investigating the characteristics of the atmospheric dust life-cycle regarding the atmospheric circulation over the Mediterranean. Two different phases are identified from the first EOF, which in total are explaining 45 % of the variance. They are characterized by the propagation of the subtropical ridge into the Mediterranean basin, the position of the Saharan heat low and the predominance Iberian heat low and discussed illustrating a dipole pattern for enhanced (reduced) dust emission fluxes, stronger (weaker) meridional dust transport, and consequent increased (decreased) atmospheric dust concentrations and deposition fluxes. In case of a predominant high pressure zone over the western and central Mediterranean (positive phase), a hot spot in dust emission flux is evident over the Grand Erg Occidental and reduced level of atmospheric dust loading occurs over the western Mediterranean basin. The meridional transport in northward direction is reduced due to prevailing northerly winds. In case of a predominant heat low trough linking the Iberian and the Sahara heat low (negative phase), meridional dust transport toward the western Mediterranean is increased due to prevailing southerly winds resulting into an enhanced atmospheric dust loading over the western Mediterranean. Altogether, results form this study illustrate the relevance of knowing dust source location in concert with atmospheric circulation. The study elaborates the question on the variability of dust transport toward the Mediterranean and Europe in dependence on the atmospheric circulation as a driver for dust emission and a determinant for dust transport routes, exemplarily for the two-month period June to July 2013. Ultimately, outcomes from this study contribute to the understanding of the variance in dust transport into a populated region.

scholarly journals Development of a dynamic dust source map for NMME-DREAM v1.0 model based on MODIS Normalized Difference Vegetation Index (NDVI) over the Arabian Peninsula

2019 ◽  
Vol 12 (3) ◽  
pp. 979-988 ◽  
Author(s):  
Stavros Solomos ◽  
Abdelgadir Abuelgasim ◽  
Christos Spyrou ◽  
Ioannis Binietoglou ◽  
Slobodan Nickovic
Keyword(s):  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Mesoscale Model ◽  
Dust Emission ◽  
Atmospheric Model ◽  
Fine Tuning ◽  
Dust Source ◽  
Dust Sources ◽  
Modis Aod ◽  
Dynamic Source

Abstract. We developed a time-dependent dust source map for the NMME Dust Regional Atmospheric Model (DREAM v1.0) based on the satellite MODIS Normalized Difference Vegetation Index (NDVI). Areas with NDVI <0.1 are classified as active dust sources. The updated modeling system is tested for dust emission capabilities over SW Asia using a mesoscale model grid increment of 0.1∘×0.1∘ for a period of 1 year (2016). Our results indicate significant deviations in simulated aerosol optical depths (AODs) compared to the static dust source approach and general increase in dust loads over the selected domain. Comparison with MODIS AOD indicates a more realistic spatial distribution of dust in the dynamic source simulations compared to the static dust sources approach. The modeled AOD bias is improved from −0.140 to 0.083 for the case of dust events (i.e., for AOD >0.25) and from −0.933 to −0.424 for dust episodes with AOD >1. This new development can be easily applied to other time periods, models, and different areas worldwide for a local fine tuning of the parameterization and assessment of its performance.

scholarly journals The role of Southern Africa as a dust precursor to East Antarctica

2020 ◽  
Author(s):  
Stefania Gili ◽  
Aubry Vanderstraeten ◽  
Mathieu Cazaunau ◽  
Amelie Chaput ◽  
Jean-Francois Doussin ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Southern Africa ◽  
Mineral Dust ◽  
Numerical Models ◽  
Dust Emission ◽  
East Antarctica ◽  
Namib Desert ◽  
Earth Planet ◽  
Dust Sources ◽  
Dronning Maud Land

&lt;p&gt;Identifying the provenance of mineral dust depositions in Antarctica is crucial to reconstruct Southern Hemisphere (SH) atmospheric circulation, validate numerical models, evaluate their contribution as micronutrients in the Southern Ocean and assess their control on the climate changes. For the last few decades, it has been demonstrated Southern South America (SSA) is the main precursor of dust reaching Antarctica during both ice ages and interglacial periods (e.g. Gili et al., 2017, 2016). However, the origin of modern dust depositions on the Antarctic continent is still poorly constrained. Back in the nineties, together with SSA, Australia, New Zealand, and Southern Africa were firstly identified as dust contributors to East Antarctica (EA) (e.g. Delmonte et al., 2004a). Since then, only SSA and Australian dust sources benefited from detailed studies. While some works identified the Makgadikgadi and Etosha Pans as southern Africa's major mineral dust sources in the SH, it was not until recently the Namib Desert coastal areas were described as another important regional dust sources. Within the Namib Desert and along the coast, the Kuiseb (K), Omaruru (O) and Huab (H) dry riverbeds are the three main areas identified as the dustiest ones with the higher frequency of dust emission events (Von Holdt et al., 2017). Here we use Sr, Nd and Pb isotopes (measured on HR-MC-ICP-MS) to characterize and evaluate the influence of this region in Southern Africa as a dust source to EA. Samples collected in K, O and H desertic areas were analyzed together with snow samples collected along a ~250 km N-S transect (defined from the coast to inland) at seven different sampling sites in the surroundings of Dronning Maud Land, EA. In addition, using the bulk of the Huab region, dust aerosols were generated into an atmospheric simulation chamber (CESAM) to reproduce, mechanically the saltation and sandblasting processes responsible for the release of mineral dust in natural conditions. Our isotopic results show Namibia&amp;#8217;s coast emerged as another possible source end-member, together with some regions in SSA, that supply dust to EA during warmer periods.&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Delmonte, B., Basile-Doelsch, I., Petit, J.R., Maggi, V., Revel-Rolland, M., Michard, A., Jagoutz, E., Grousset, F., 2004. Comparing the EPICA and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods. Earth-Sci. Rev. 66, 63&amp;#8211;87.&lt;/p&gt;&lt;p&gt;Gili, S., Gaiero, D.M., Goldstein, S.L., Chemale, F. Jr., Koester, E., Jweda, J., Vallelonga, P., Kaplan, M.R., 2016. Provenance of dust to Antarctica: a lead isotopic perspective. Geophys. Res. Lett. 43. http://dx.doi.org/10.1002/2016GL068244.&lt;/p&gt;&lt;p&gt;Gili, S., D.M. Gaiero, S.L. Goldstein, F. Chemale, J. Jweda, M.R. Kaplan, R.A. Becchio, and E. Koester (2017). Glacial/interglacial changes of Southern Hemisphere wind circulation from the geochemistry of South American dust. Earth Planet. Sci. Lett., 469, 98-109, doi: 10.1016/j.epsl.2017.04.007.&lt;/p&gt;&lt;p&gt;Von Holdt, JR., Eckardt FD., and Wiggs GFS., 2017. Landsat identifies aeolian dust emission dynamics at the landform scale. Remote Sensing of Environment 198., 229&amp;#8211;243.&lt;/p&gt;

Mineral dust aerosol from Saharan desert by means of atmospheric, emission, dispersion modelling

2011 ◽  
Vol 8 (4) ◽  
pp. 7313-7338 ◽  
Author(s):  
F. Guarnieri ◽  
F. Calastrini ◽  
C. Busillo ◽  
M. Pasqui ◽  
S. Becagli ◽  
...  
Keyword(s):  
Prediction Models ◽  
Mineral Dust ◽  
Dust Emission ◽  
Atmospheric Model ◽  
Saharan Dust ◽  
Emission Model ◽  
Good Correspondence ◽  
Comparison Of The Results ◽  
Modelling System

Abstract. The application of Numerical Prediction Models to mineral dust cycle is considered of prime importance for the investigation of aerosol and non-CO2 greenhouse gases contributions in climate variability and change. In this framework, a modelling system was developed in order to provide a regional characterization of Saharan dust intrusions over Mediterranean basin. The model chain is based on three different modules: the atmospheric model, the dust emission model and transport/deposition model. Numerical simulations for a selected case study, June 2006, were performed in order to evaluate the modelling system effectiveness. The comparison of the results obtained in such a case study shows a good agreement with those coming from GOCART model. Moreover a good correspondence was found in the comparison with in-situ measurements regarding some specific crustal markers in the PM10 fraction.

scholarly journals Evaluating the Relative Importance of Northern African Mineral Dust Sources Using Remote Sensing

2019 ◽  
Author(s):  
Natalie L. Bakker ◽  
Nick A. Drake ◽  
Charlie S. Bristow
Keyword(s):  
Remote Sensing ◽  
Mineral Dust ◽  
Boreal Winter ◽  
Relative Importance ◽  
Alluvial Deposits ◽  
Dust Source ◽  
Total Dust ◽  
Dust Sources ◽  
Dust Mass ◽  
Winter Dust

Abstract. Mineral dust from the Sahara and Sahel provides the Amazon Basin with essential nutrients, although the process is still poorly understood. There is little understanding where the dust is coming from, and thus what the concentration of nutrients in the dust is. This information, however, is vital to assess the impact it will have on the Amazon. This study analyses northern African dust sources of the boreal winter dust seasons between the years 2015–2017. It utilises high spatio-temporal resolution remote sensing data from SEVIRI, MODIS, VIIRS and Sentinel-2 to identify dust sources, classify them according to a geomorphic dust source scheme, and quantify the relative importance of source regions by calculating the total dust mass they produce. Results indicate that paleolakes emit the most dust, with the Bodélé Depression as the single largest dust source region, however, that alluvial deposits also produce a substantial amount of dust. During the boreal winter dust seasons of 2015–2017, ~ 36 % of the total dust mass emitted from northern Africa was associated to alluvial deposits, yet this geomorphic category has been relatively understudied to date. Furthermore, sand deposits were found to produce relatively little dust, in contrast to the results of other recent studies.

scholarly journals A New Circulating Accumulation Emission Model for Assessing Dust Emission From Open Pit Mine

2021 ◽  
Author(s):  
TANG Wanjun ◽  
LI Fengming
Keyword(s):  
Dust Emission ◽  
Open Pit Mine ◽  
Monitoring Data ◽  
Open Pit ◽  
Emission Model ◽  
Initial Value ◽  
Dust Source ◽  
Background Value ◽  
Dust Diffusion ◽  
And Diffusion

Abstract In order to reduce the inaccuracy of using the monitoring data outside the pit to evaluate the unorganized emission dust source of open pit mine, the circulating accumulation emission model is established. Based on the model, the monitoring data in the pit can be converted into the dust emission from the pit. Main conclusions include: (1) the circulating accumulation emission model is suitable for the dust diffusion process in open pit mine. The model contains three part, which correspond to dust emission, retention and diffusion in open pit mine. (2) The initial value of the dust in the pit before the team operation has little influence on the final stable value. (3) The dust background value of surrounding environment monitored outside the pit can not be directly used. When the dust enters the pit, it will accumulate under the action of eddy current. To eliminate the effect of background value, the monitoring data should be subtracted by the accumulated value. (4) The dust emission from the pit can be calculated in a certain monitoring period based on the circulating accumulation emission model. Hence the dust emission assessment of open pit can be completed more efficiently based on this model.

scholarly journals North African mineral dust sources: new insights from a combined analysis based on 3D dust aerosol distributions, surface winds and ancillary soil parameters

2020 ◽  
Vol 20 (23) ◽  
pp. 15127-15146
Author(s):  
Sophie Vandenbussche ◽  
Sieglinde Callewaert ◽  
Kerstin Schepanski ◽  
Martine De Mazière
Keyword(s):  
Mineral Dust ◽  
Dust Emission ◽  
Satellite Observations ◽  
Dust Aerosol ◽  
North African ◽  
Near Surface ◽  
Dust Sources ◽  
Low Altitude ◽  
Spatio Temporal ◽  
The Impact

Abstract. Mineral dust aerosol is a key player in the climate system. Determining dust sources and the spatio-temporal variability of dust emission fluxes is essential for estimating the impact of dust on the atmospheric radiation budget, cloud and precipitation formation processes, the bio-productivity and, ultimately, the carbon cycle. Although much effort has been put into determining dust sources from satellite observations, geo-locating active dust sources is still challenging and uncertainties in space and time are evident. One major source of uncertainty is the lack of clear differentiation between near-source dust aerosol and transported dust aerosol. In order to reduce this uncertainty, we use 3D information on the distribution of dust aerosol suspended in the atmosphere calculated from spectral measurements obtained by the Infrared Atmospheric Sounding Interferometer (IASI) by using the Mineral Aerosols Profiling from Infrared Radiance (MAPIR) algorithm. In addition to standard dust products from satellite observations, which provide 2D information on the horizontal distribution of dust, MAPIR allows for the retrieval of additional information on the vertical distribution of dust plumes. This ultimately enables us to separate between near-source and transported dust plumes. Combined with information on near-surface wind speed and surface properties, low-altitude dust plumes can be assigned to dust emission events and low-altitude transport regimes can be excluded. Consequently, this technique will reduce the uncertainty in automatically geo-locating active dust sources. The findings of our study illustrate the spatio-temporal distribution of North African dust sources based on 9 years of data, allowing for the observation of a full seasonal cycle of dust emissions, differentiating morning and afternoon/evening emissions and providing a first glance at long-term changes. In addition, we compare the results of this new method to the results from Schepanski et al. (2012), who manually identified dust sources from Spinning Enhanced Visible and InfraRed Imager (SEVIRI) red–green–blue (RGB) images. The comparison illustrates that each method has its strengths and weaknesses that must be taken into account when using the results. This study is of particular importance for understanding future environmental changes due to a changing climate.

scholarly journals The Mineral Dust Cycle in EMAC 2.40: sensitivity to the spectral resolution and the dust emission scheme

2012 ◽  
Vol 12 (3) ◽  
pp. 1611-1627 ◽  
Author(s):  
G. Gläser ◽  
A. Kerkweg ◽  
H. Wernli
Keyword(s):  
Atmospheric Chemistry ◽  
Mineral Dust ◽  
Dust Emission ◽  
Dust Particles ◽  
Global Maximum ◽  
Polar Regions ◽  
Model Resolution ◽  
Qualitative Comparison ◽  
Dust Source ◽  
Grid Points

Abstract. This first detailed analysis of the mineral dust cycle in the ECHAM5/MESSy Atmospheric Chemistry (EMAC) model system investigates the performance of two dust emission schemes, following the approach of Balkanski et al. (2004) and Tegen et al. (2002), respectively, and the influence of the horizontal model resolution. Here the spectral resolutions T42, T63, T85, and T106 are investigated. A basic sulphur chemistry, enabling the coating of insoluble dust particles to make them soluble, is employed in order to realistically describe the ageing and wet deposition of mineral dust. Independent of the dust emission scheme the five-year simulations with the horizontal resolutions T42 and T63 produce unrealistically high emissions at some grid points in the Tarim Basin in Central Asia, leading to very high dust loads in polar regions. With these coarse resolutions, dust source grid points in the basin and elevated grid points of the Himalayas with high wind speeds cannot be distinguished, causing this overestimation. In T85 and T106 these regions are well separated and considerably less dust is emitted there. With the chosen model setup, the dust emission scheme by Balkanski et al. (2004) places the global maximum of emissions in the Thar Desert in India. This is unrealistic as the Sahara Desert is known to be the largest dust source in the world. This is the main deficiency of this scheme compared to the one by Tegen et al. (2002), which, based on a qualitative comparison to AEROCOM data, produces a very reasonable distribution of emissions and dust loads in simulations with resolutions T85 and T106. For future climate simulations with EMAC focusing on mineral dust, we recommend to use the dust emission scheme by Tegen et al. (2002) and a model resolution of at least T85. Simulations of two selected episodes and comparison to observational data sets show that in this model configuration EMAC is able to realistically simulate also intense, episodic events of dust emission and long-range transport.

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