Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects of anthropogenic ff with a minimum in North 2 − 2 10163 10164 ect on radiative transfer and climate, it is important to ff , and S. L. Nasiri 1 ect on radiative forcing which may be comparable to other ff with a maximum in India to 0.12 gm 2 − , B. Chen 1 , J. Liu 1 This discussion paper is/has beenand under Physics review (ACP). for Please the refer journal to Atmospheric the Chemistry corresponding final paper in ACP if available. Key Laboratory for Semi-Arid Climate Change of the Ministry ofDepartment Education, of College Atmospheric of Science, Texas A&M University, College Station, TX, USA Abstract Anthropogenic dusts are those producedare by mainly human cropland, activities pasture, on andload disturbed urbanized soils, which regions which and includes are naturalpogenic a subset sources dusts of from the is total desertmagnitude, still dust and regions. very on Our their limited knowledgeanthropogenic e due of aerosols. To to anthro- understand atotal the global lack contribution dust of of load anthropogenicidentify data and dust them its on to from e source total the pogenic dust. distribution dust In from and this natural study, dustPathfinder a is Satellite new proposed Observation technique by (CALIPSO) using forheight dust Cloud-Aerosol distinguishing retrievals and Lidar anthro- along planetary and with boundary Infrared abution layer land of (PBL) use dust dataset. isdust Using analyzed sources this and to technique, regional the the andanthropogenic global relative global dust distri- contribution emissions aerosol of are due to estimated. anthropogenicity, human Results transportation, and activity, reveal and such natural that as overgrazing, local accounts agriculture,dust industrial load. for Of activ- about these 25 anthropogenic %and dust of semi-wet aerosols, the more regions. than Annual global 53 mean continental range % anthropogenic from come dust from 0.42 gm column semi-arid burdenAmerica. (DCB) A values better understandingcus of on anthropogenic human dust activities emissionbetter in will able these enable to us critical improve to global regions fo- dust and models with and such to knowledge explore we the will e be emission on radiative forcing, climate change and air quality in the future. 1 Introduction Dust accounts for someand of the plays highest an atmosphere important mass loadings role in in the modulating atmosphere radiative forcing and climate via a num- 1 Atmospheric Sciences, Lanzhou2 University, Lanzhou, 730000, China Received: 5 March 2015 – Accepted: 10Correspondence March to: 2015 J. – Huang Published: ([email protected]) 7 AprilPublished 2015 by Copernicus Publications on behalf of the European Geosciences Union. Detection of anthropogenic dust using CALIPSO lidar measurements J. Huang Atmos. Chem. Phys. Discuss., 15, 10163–10198,www.atmos-chem-phys-discuss.net/15/10163/2015/ 2015 doi:10.5194/acpd-15-10163-2015 © Author(s) 2015. CC Attribution 3.0 License. 5 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect emissions to understand ff 10166 10165 ects the radiative forcing. It is critical to quantify the relative importance of culty of identifying and measuring them, which derives from the strong het- ff ffi erent types of dust sources and the factors that a ff The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) However, the assessment of the role of anthropogenic activity in the atmospheric Generally, anthropogenic dust originates mainly from agricultural practices (harvest- satellite carries a lidar to actively remotely sense cloud and aerosol vertical profiles There are large uncertainties regardingulating the dust impact of emission anthropogenic directlydiative activities (Sokolik on forcing mod- and due to Toon, 1996) dusticcating e.g., and water by understanding bodies, disturbing of and soils,requires the removing indirectly, an vegetation ra- by improved cover, data changing or set.their des- climate Although environment and there and are the many thereby hydrologicalproblem examples causing to cycle of separately an humans quantify altering additional bothmineral dust the aerosol burden, natural (Sagan and it et anthropogenicthe is al., components dust a 1979). of production challenging the Sokolik rate is andthe linearly Toon amount (1996) proportional of roughly to anthropogenic theconverted assumed mineral dust that to aerosols source through deserts area assessments by andthropogenic of estimated human contribution the activities. to land Tegen mineral area the and dust atmosphere Fung by to (1995) a be estimated three-dimensionet 30 atmospheric the al. to dust (2004) an- transport provided 50 % model. ansuggested of updated Later, that Tegen estimate the only by total comparing 5calibrating dust observations to a of burden dust-source 7 visibility in % model and ofvations. with Understanding emission mineral of indices dust the derived comes emissionsto from of from the dust-storm anthropogenic di anthropogenic obser- dust sources iserogeneities by still in very the limited sources due the (Mahowald first et al., studies 2002). toestimated Ginoux that estimate et 25 anthropogenic % al. of dust (2012)Resolution dust emissions Imaging was is Spectroradiometer one using anthropogenic (MODIS) of by observations. Deepbination using Blue They with observation satellite a data, products, land-use the in fraction Moderate only com- dataset. be A retrieved limitation over of bright theseocean surfaces products surfaces. in Additionally, is MODIS the that products visible they do wavelengths,distribution can not excluding and include forests information therefore and about cannot vertical marine readily seasalt exclude aerosol natural that dust are aerosol transported from over anthropogenic deserts sources. or ber of complex processes.large optical While depths, mineral the existing dustsources atmospheric alone has dust (Tegen load and a cannot Fung, be wide 1995).disturbed explained The distribution by soils atmosphere natural by and dust load human relatively that(Tegen activities, and originates which Fung, from can 1995), such bein as interpreted land turn, as use a “anthropogenic” practices, can dust increase dust loading which, dust cycle is limited by the accuracy of the available data sets (Mahowald et al., 2002). the di ing, ploughing, overgrazing), changes inand surface Aral water Sea, (e.g., Owens shrinkingindustrial Lake), of practices the and (e.g., Caspian also cementthe from production, last urban transport) few practices (Prospero decades,springs a (e.g., et in combination construction), al., semi-arid of 2002). and and more semi-wet Over human regions frequent and activity warmer changes and have in dryer, vegetatedLuo, likely land winters cover 2003; increased and due anthropogenic Moulin to demonstrated dust and that emissions the Chiapello, development (Mahowald of 2004;large agriculture and increase Tegen in of the et dust Sahel emission al.,that corresponded and up to deposition 2004). to in a half the very Mulitza of region.disturbed the The et soils modern current (Tegen et al. atmospheric consensus al., is dust 2004). (2010) the In load additional, direct originates Sokolik solar from and radiative anthropogenically- Toon forcing (1996)and by revealed that anthropogenic the dust forcing has by athe wide anthropogenically-generated range forcing dust of by aerosols uncertainty other maythropogenic anthropogenic be dust aerosols. comparable emission Therefore, to a isthus changes clear critical in understanding land for of use predictingin policies) an- the will how future influence changes dust (Okin emission, et in loading, al., land and 2011). deposition usage (and the global dust cycle andnoted by historical Okin and et possible al. future (2011) changes and in Bullard dust et emissions, al. as (2011). 5 5 10 15 20 25 15 20 25 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ◦ 1 (if the , and the = v δ 70 in Version 3. Based on | ≥ (Liu et al., 2010). The CAD score CAD | 0 532 β erent surface vegetation types, and was ) greater than 0.075 as dust (Omar et al., ff v cient, δ ffi 10167 10168 cients. Chen et al. (2013) noted that the impact of ffi 101 to 105. The larger the magnitude of the CAD score, − , the layer-integrated volume depolarization ratio, 0 cient and backscatter and additional profile information. In ad- χ ffi spatial resolution, includes 17 di ◦ 0 (the lidar ratio is unchanged during the extinction retrieval) and QC = The CALIPSO Level 2 lidar VFM product (Liu et al., 2004; Vaughan et al., 2004) pro- The Level 2 Aerosol Profile Product (Young and Vaughan, 2009) provides profiles of feature mean attenuated backscatter coe vides information about cloud and aerosolVersion 3 layer VFM boundaries data, and the positions. cloud In aerosoland CALIPSO discrimination aerosols (CAD) based algorithm separates on clouds multi-dimensionaltensity histograms and of spectral scattering dependence), propertiesintegrated that (e.g., color is, in- ratio, the altitude-and latitude-dependent feature reflects their confidence thata the cloud, feature on under athe consideration scale higher is from our either confidencethat an that the confidence the aerosol in classification or the is classification correct. is high Liu with et al. (2010) revealed particle extinction coe 2.2 Land cover data The Collection 5.1 MODISused in global this land study cover tohas provide type 0.05 anthropogenic product dust source (MCD12C1) types. from The 2011 MCD12C1 product is et al., 2007a, b,color 2009). ratio This profiles study along uses5 km Level with 1 Aerosol the backscatter, Profile Level depolarization 2tifying Products. ratio, Vertical The non-spherical and Feature depolarization particles, Mask ratio andspherical (VFM) is it aerosols products a can (Liu and useful distinguish eters indicator that between al., for have atmospheric 2004). volume iden- depolarization dust The2009; ratio and CALIPSO Mielonen ( et algorithm al., classifiesof 2009). dust aerosol Mielonen is lay- et more al. reliablecan than (2009) be classification also used of confirmed fine to aerosols that distinguishratio because classification is non-spherical depolarization sensitive aerosols ratio mainly from to spherical particle ones size. while the color this, we only include featuresstudy. with absolute values of CAD score greater than 70 in this dition, the CALIPSO extinction quality controlQC (QC) flags were also provided.retrieval Extinction is constrained) aredepth chosen by in integrating this extinction coe paper,the which screening procedure are in used this to specific calculate case is optical negligible. cell. Because we are focusing on sources of anthropogenic dust in this paper, we limit 2.1 CALIPSO data This study relies on(CALIOP) the for CALIPSO dust Cloud-Aerosolter detection. Lidar at CALIOP with two acquires Orthogonal wavelengthsa vertical Polarization (532 near profiles and nadir-viewing 1064 of nm) geometry elastic and during backscat- linear both depolarization day at and 532 nm night from (Winker et al., 2007; Hu (Winker et al., 2007;into Hu the detection et of al.,vertical global 2007a, resolution anthropogenic b, and dust 2009).for polarization detection emission CALIPSO ratio. of due can In anthropogenic to dust provideand this emissions its new use study, by measurement insight we using this of CALIPSO developthis to lidar a study, measurements analyze new while its technique theoutlined global in method distribution. Sect. for Section 3. separatingburden. Section 2 Section anthropogenic 4 presents discusses 5 dust the the presents fromconclusions calculation data the are natural of presented global used anthropogenic dust in distribution dust in Sect. is of column 6. anthropogenic dust. Finally, the 2 Data developed by the Internationalland Geosphere-Biosphere and Programme Belward, data 1997; (IGBP)as Friedl (Love- et well al., as 2010). the It sub-grid provides frequency the distribution dominant of land land cover cover type classes within each 0.05 5 5 10 20 25 15 20 15 10 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent anthro- ff 10170 10169 latitude and longitude resolution. The CRU Global Climate Dataset temperature ◦ Figure 2 shows a schematic of dust sources and vertical and horizontal transport pro- deserts can undergo long-range transporttary to boundary other layer regions (PBL) by toHorizontal lifting the through free transport the troposphere, plane- of as confirmedet natural by al., dust Chen 2010; et aerosols al. Yuwithin occurs (2013). et the mainly PBL. al., However, above 2012). itet the is Only al., this PBL 2012). a fraction (Jordan Dusts small thatinately from may amount trapped other be of in land most this relevant surface thetravel, to are types dust PBL conducted air and enters where (Stull, quality pollution 1988, and (Yu industrialthropogenic sources 2000). remains dust and We are from go commercial predom- natural through dust activities, fourtotal in steps except dust the to load for CALIPSO discriminate (both data. air an- source natural The region and first of anthropogenic). step the is The dust. to Thestep second third detect is step step the to is is determine to to which determinewithin determine the dust PBL. the height is of anthropogenic PBL, dust and i.e., the that final subset3.1 of the total dust Step 1: total dust detection Aerosol subtypesCALIPSO are VFM data. stored Therefore,Flags dust in in aerosols this are the paper. We identified onlyi.e., by use parameter dust absolute Feature aerosol Classification values “Feature feature for of which Classification CAD there is score high Flags” greater confidence, than of 70. Then, dust aerosol extinction co- cesses underlying our approachThe for yellow separating dots anthropogenic represent dustlines from dust indicate natural aerosol dust. lifting in the and atmosphere; turbulence, the respectively. arrows It and illustrates red that wavy natural dust from based measurement data. In 2012,pogenic Ginoux dust et by al. using proposedhas MODIS a limited deep method accuracy to blue over detect relatively products, bright, anthro- and but land comprehensive MODIS, surfaces. results, a In order we passive tothropogenic developed instrument, get a dust more new accuracy and method assess toscale anthropogenic by separate using impacts natural CALIPSO on and measurements. dust an- emissions at the global pogenic dust source types: redyellow represents represents urban cropland, areas, orange andrectangles represents green denote grassland, four represents regions cropland thatAmerica, mosaics. will and be Africa. The emphasized four later: black East China, India,2.3 North Precipitation data Anthropogenic dust emissions dependcipitation on and soil climate moisture state content regime.mate In and state this therefore regime. study, on we The use pre- UniversityClimate precipitation of Dataset as East a provides Anglia proxy the Climate for monthlyareas, Research cli- excluding mean Unit Antarctica (CRU) precipitation (New Global climatologies et for al.,is 1999), global based which land on is used analysisat in of 0.5 this over study. The 4000 data individual set and precipitation, weather estimates station were records madeJones, and for 2005). 80–100 is In % this provided of study theaverage the land for monthly surface the mean (Mitchell period climatology and was 1961–1990. calculated relative to the 3 Dust detection and identification methods It is a challenge(Sagan et to al., distinguish 1979; the Sokolik and anthropogenic Toon, 1996) dust due component to the from indirect natural nature dust of the satellite- our study toMosaics. three Cropland agricultural Mosaics surface arethe types: lands landscape Croplands, (Friedl with et Grasslands, a al.,of and mosaic 2002). anthropogenic Cropland Because of dust, urban croplands we environmentsGlobal less can Rural-Urban get than also Mapping information be Project 60 % about sources (GRUMP)Fig. v1 of the 1, (Schneider extent we et of summarize al.,types the 2010) urban described dataset. geographical areas above. In distribution from The of the colors the indicate anthropogenic the dust locations source of the four di 5 5 15 20 25 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ), τ 1, which = . 1 − 0 and QC = cient of 0.73 (Liu et al., ffi ) in Eq. (1). 2 erence in optical properties between − 0.25 can be used to discriminate dust ff E) and natural dust source (Taklimakan: = ◦ 0 δ measuring 0.01-by-0.001 sr 0 for both anthropogenic dust and natural dust γ 0 10172 10171 and the layer integrated attenuated backscat- ∆ γ 0 − δ 0 δ and ∆ 0 c, etc. We assume that anthropogenic dust will typi- δ 0.23 can be used to separate anthropogenic dust from N, 114.0–118.0 ffi ◦ = 0 δ E). Because spring (March to May) is the most active season ◦ , can be used to explore the di 0 γ N, 78.0–83.0 ◦ cient ffi cients are integrated under the condition of extinctions QC We modified the maximum standard technique developed by Jordan et al. (2010) We can use CALIPSO to determine PBL height because, in general, the PBL is In Fig. 3a, we can see that a threshold of ffi are chosen from CALIPSO’s aerosoloptical profile depth as product. well Next, as we dust calculated column dust burden aerosol (gm cally be emitted from cropland,pogenic grasslands, surface”), and urban will surfaces have (referred thinnerin to PBL, dust as and aerosol “anthro- will layers, rarely will before, lifted we be restrict into predominately the our trapped free source atmosphere regionsland by to surfaces wind the from and urban, the turbulence. grassland, There- cropland, MODIS and and mosaic GRUMP crop- datasets, as3.3 seen in Fig. Step 1. 3: determination of PBLIn height this step, wedust determine aerosol and from used dust PBL sourcesit height above is to the important exclude anthropogenic long-distance to surfacedust. transport described accurately of above, determine so PBL height to separate outcapped the by anthropogenic agradient temperature of inversion backscatter seen thatture by inversion tends lidar and to is theMelfi trap simultaneous almost et decrease always moisture al., in associated 1985). and moisture withaerosol Thus, content aerosols. scattering the this (Palm gradient definition tempera- The is et of analogous al.,inition. the to 1998; PBL the McGrath-Spangler top more and conventional as thermodynamicspective the Denning def- Analysis location (2012) for of Research revealed the and Applications thatof maximum (MERRA) the the PBL estimates derived depths Modern-era from are the within Retro- maximum 25 % standard technique (Jordan et al., 2010) by 3.2 Step 2: selection of sourceAs regions of stated anthropogenic previously, dust anthropogenicovergrazing, dust construction, mainly tra comes from harvesting, ploughing, 2014). 3.4 Step 4: identification of anthropogenicThe dust final within step PBL is tolayer identify the integrated anthropogenic depolarization dust within ratio the PBL. Two parameters, the natural dust anding anthropogenic output dust. of this Aspopulation density, step, an and we land illustration chose coverdust of distribution, two (North China: to typical the 35.0–39.0 represent areas sources process based of and anthropogenic on result- dust optical depth ( and derived global PBL heightsMcGrath-Spangler using and this Denning method, which (2012). arefavorably And, to consistent we the with found ground-based results that of lidarvatory at this of the technique Lanzhou Semi-Arid compared University Climate (SACOL) and with Environment a Obser- correlation coe CALIPSO, which is better than radiosonde(Angevine estimates et of al., space/time 1994). average PBL depth ter coe 38.0–40.0 for dust emission in thetime Taklimakan region, CALIPSO 4 years measurements (2007 through weredust 2010) aerosol. used of Because spring, to anthropogenic day- look dustdust has at is little at the seasonal its dependence optical minimumthe and properties in optical natural autumn, of properties we of natural used anthropogenictribution 4 dust. years of For of the these autumn layer-integrated two measurements seasons, to the look statistical at dis- from the entire profileoccurrences and within within grid boxes the of PBL, respectively was constructed by summing e based on the entirethat profiles a from lower the threshold Taklimakan of and North China. Figure 3b shows 5 5 10 15 20 25 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (1) ) to dust τ ) from the a τ resolution de- ◦ 1.25 is the dust extinction × ext ◦ is the dust optical depth Q τ cient through the parame- 70) (Liu et al., 2010) and ffi | ≥ , and 1 − CAD g | 2 0.6 m ) can be calculated by integrating the CAD = τ ) and anthropogenic DOD ( cient of dust aerosol over the height of the t ciency. Ginoux et al. (2012) used daily global ε τ ffi is the density of dust, 10173 10174 ffi ρ 2.5, = ext 1) based on the study of Chen et al. (2013) were se- Q = , 3 − ) was calculated following Ginoux et al. (2001): ective radius, ff M 0 or QC = 2600 kgm τ 9.6 % of anthropogenic dust is misclassified as natural dust and 8.7 % is the mass extinction e 1 ε = ε ∼ cients with higher confidence levels ( ρ = ffi τ is the dust e ff ff e e ext r Q ρr 1.2 µm, 3 4 = ciency, and = After calculating global total DOD ( A detailed flow chart of the anthropogenic dust detection algorithm is shown in Fig. 4. Therefore, anthropogenic dust could be accurately distinguished from natural dust ff ffi e CALIPSO profile products between Januaryto 2007 calculate and dust December column 2010, burdens. we The were conversion able from dust optical depth ( column mass burden ( M dust layer. Where, lected. Therefore, dust optical depth (DOD, and QC quality-controlled extinction coe e 4 Calculation of anthropogenic dust columnBased burden (DCB) on thepogenic detection dust and methods calculate anthropogenic described dustdust column column burden above, as burden. a we First, subset we of areter used the “Atmospheric the global able Volume dust Description” to extinction which coe and identify is clouds used in anthro- to the discriminate CALIPSOtinction between Level coe 2 aerosols aerosol extinctionquality-control profile (QC products. Then, dust ex- the PBL. This problemQuantitatively, should be kept inof mind in natural the dust following isanthropogenic results dust, misclassified and respectively. discussion. as anthropogenic dust within the PBL along with the DOD from MODIS deep bluethis aerosol study, products we and follow converted thoser it empirical into values column taken burden. by In Ginoux et al. (2012) and assume by the above steps. Inevitably, therenatural are dust some misclassifications owing of to anthropogenic and anthropogenic dust mixed with natural dust above and below natural dust within the PBL.to The the larger PBL threshold is mainly valueChina for due leads to the to a entire the larger fact profile depolarizationlayer-integrated that compared ratio. Furthermore, attenuated natural anthropogenic dust backscatter dust transport has ishuman above lower the because activities PBL and anthropogenic in generally dust North has mixed lower produced with non-spherical. by other Natural dust typeso anthropogenic is aerosols dust more within has non-spherical lower the layer-integrated than depolarization PBL, anthropogenic ratio which dust, than natural dust. derived from the CALIPSO retrievals. 5 Results The global distribution of seasonal mean, total DOD with 1.25 rived from CALIPSO measurementswhich for shows 2007 that dust throughern covers 2010 Hemisphere. a are The larger presented Taklimakan areathe and in in deserts Gobi Fig. the on deserts 5, Northern thegions, in Hemisphere Indian China subordinate than Subcontinent (Qian only South- (Middleton, et to2002; al., 1986) Liu North 2002) are et Africa al., and majorwhich and 2008). dust These stretch the source major from Arabian re- dust theand Peninsula sources western Sahel (Prospero are regions, coast located et the in of al., desert the Arabian North (Herman broad Peninsula, Africa et “dust northern al., to belt” associated India, 1997; China, with the Prospero covering topographical Tarim et the Basin basinsmountainous al., and Sahara in or 2002; Gobi these Liu plateau arid et regionsProspero regions, al., or et on 2008), in al. and land intermountain are (2002). adjacent basins usually to In as high discussed these in source detail regions by the annual rainfall is generally low, 5 5 25 20 15 10 10 15 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erence is that air in Fig. 8, and the ff erence with Ginoux 1 ff − erent than the seasonal ff ), with anthropogenic DCB showing minimal 10176 10175 n τ to a maximum of 2000 mmyr 1 − . The average anthropogenic dust column burdens cor- 1 − Figure 8 shows a comparison of global dust column burdens as function of clima- Figure 7 shows the global distribution of the percentage of anthropogenic dust within Figure 6 illustrates the global distribution of seasonal mean anthropogenic DCBs. Using Eq. (1), we calculated the global annual mean total dust column burden (DCB) responding to the precipitationfound intervals that anthropogenic are dusts plotted mainly comethe for from whole each semi-arid year. interval. and The semi-wet From semi-aridregions, regions Fig. regions over which are 8 are transition defined we zones as between areas arid where and precipitation semi-wet is less than potential evapora- tological mean precipitation forthough the precipitation spring, is related summer, to autumn, surfaceis temperature, and the the simplest winter long-term index mean seasons. for precipitation classifyingtially Al- climate from regions. The less meaninterval than precipitation varies value 100 spa- mmyr is 100 mmyr pattern of natural dust optical depth ( with human activities in many localEastern regions. Several North features are America, evident India, inthan these East maps. 60 China %, and which Europe correspondregions. show Lower to high percentages highly occur percentages, populated over larger Western or North intensively America, cultivated North agricultural Africa, etc. the total dust column burden over land. This illustrates the significance of dust related seasonal variation owing to anthropogenic dust emissions which are controlled by et al. (2012): MODIS deepsurface blue (excluding algorithm forest only and retrievedproducts dust ocean) have optical not lead depth vertical to overtransported information bright a to which anthropogenic lower cannot surface dust extract bring natural burden, with a dust and bigger from MODIS result. deserts data Global seasonal mean6.1 Tg anthropogenic (autumn), DCBs and are 6.0 Tg 7.0 (winter), Tg respectively. This (spring), is 6.9 Tg di (summer), human activities and urbanChina, pollutants. India, Larger and dust Northdensities column Africa burdens in for occurred all the in seasons,year East East which in China are Africa and related due(Justice to India to et higher farmers regions population al., preparing and for 1996).accounts biomass the The for agricultural burning 8.4 global season % throughout annualpact and of the of mean grazing the dust areas anthropogenic on total the DCBthat global ocean, is we anthropogenic dust only dust 6.7 column calculated Tg, sources global burden.(including which continent account polluted In dust for dust). aerosols order 24.8 and There % to found are of avoid mainly total two the continental reasons im- dust for the sources di masses with pollution aerosolepisodes and of dust dust are mixed withban included biomass pollution in burning and our smoke, dust results instances mixedthe with which of depolarization sea-salt dust account ratio aerosol mixed is for (Omar dominated withbe et by ur- classified the al., as dust 2009). dust component In and and these the the cases DCB entire will mixture be will biased high. (summer), 73.7 Tg (autumn) andsphere 77.5 Tg is (winter), greater show inthe that global the dust annual spring burden mean in dust andwhich the burden summer. is values atmo- Huneeus from far 14 et lower models al. than range from (2011) our 6.8 pointed results. to A out 29.5 Tg, possible that reason is for this di to be 79.3 Tg. The global seasonal mean values, which are 81.5 Tg (spring), 81.0 Tg less than 200–250 mm. Significantd. seasonal During variation the of spring DODNorth is and Africa illustrated summer, and in dust the Fig. outbreaksthe Arabian 5a– are more Peninsula, most active summer season active is in inbian the the this Peninsula, more Indian Indian active dust Subcontinent Subcontinent season. belt. and and Springautumn, In Taklimakan Taklimakan, is reaching region. dust In a activities the minimum weakenpathway: Ara- rapidly in the in winter. trans-Atlantic Figure transport 5belt” clearly out of toward shows North the a America AfricanAtlantic main continent. dust all The dust North year which transport Africa long stretches dust withare the is strong the transported “dust seasonal across most dependencies the of activetransport which and pathway spring in autumn and East summer thelantic Asia pathway. least This even is active. though path And shown itas in the the is Fig. North clearly Hexi 5, Atlantic too, subordinate Corridor pathway. even though to as it the a is North not minor as At- strong or clear 5 5 25 20 15 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in 2 − with max- 2 − erence is most signif- ff in semi-arid regions. Semi- 1 . Total anthropogenic DCB is C) during the hottest months. − ◦ 1 − erence from the results of Ginoux ff 10178 10177 ), total area, total anthropogenic DCB and the a τ with minimum in North America, including 0.23 gm 2 in North Africa. The anthropogenic dust contributions to the − 2 − A histogram illustrating the relative contribution of anthropogenic and natural dust Figure 9 shows the regional distribution of annual mean anthropogenic dust column dust sources in the Saharawith and natural anthropogenic dust dust source inFigure areas, the anthropogenic 9 southern dust also Sahel. source shows Compared the areas that only anthropogenic northeast occupy dust China, 21.5 sources %. thelargest are anthropogenic North mostly DCBs China confined are to Plain,sistent located areas with over and in the the Inner North conclusions Mongolia ofdoes China in Wang Plain. not et This exceed East al. 8 is China. (2006),of days also The who per con- human find year activity. that In in dust Mongolia, northernassociated storm there China, with frequency are even pasturelands dozens where of orare there small are grasslands. centered anthropogenic high Most in dust levels dust two sources separated eastern sources by over areas, the North the continental Great America divide. Plains A and the major Great di Basin which are sources over anthropogenic dustin source Fig. surfaces 10. for Annual the mean four anthropogenic study DCB regions values is range shown from 0.42 gm et al. (2012) issources that are on heavily the intertwined east andtially side anthropogenic. on The of the largest west the anthropogenic side divideNorth DCBs of are the America. the distributed anthropogenic over divide and southeast sources of natural are dust essen- Annual mean precipitation ranges from 200 to 600 mmyr imum in India to 0.12 gm tion, and are characterized by high temperatures (30–45 wet regions cover considerableChina parts with of precipitation eastern ranging North fromlarger 600 in America, to spring Europe, 800 and and mmyr summericant Central than in in arid autumn regions. anddue There winter. to is This minimal almost di agricultural noannual and anthropogenic mean human dust anthropogenic activities observed and in DOD urban arid ( pollutions. regions Table 1 shows Emission of soil andprocess mineral that dust has particles global from consequences the (Okin earth’s et surface al., is 2011), a such small as scale cloud formation East China and 0.24 gm regional emission from EastAmerica China with and 73.9 India %, are respectively.nomenon in There 91.8 that is East and China a 76.1 and %,by India possible with more followed explanation larger intense by population of agricultural densities North the and are characterized human above activities. phe- 6 Discussion and conclusions burden derived from CALIPSO measurements inAmerica four and regions: North East Africa. China, Table 2 India,percent lists North of their each latitude region and that longitude isand ranges, considered the the to area annual contribute and to mean anthropogenic anthropogenicsources dust occupy DCB emissions are of distributed relatively the evenly regions.source over the In area region; India, the is anthropogenic anthropogenic 70.2 dust dust and % human of activities the (Prasad et total al.,10 2007). area that For which the North southern is Africa, Sahel weciated characterized also dust with by note sources biomass in intense are burning Figs. overwhelmingly agricultural 9 aerosols, anthropogenic, and and are there asso- is a clear separation between natural percent contribution to total DCBregions. from wet, In combined wet semi-arid regions andthe semi-wet, the total and mean DCB arid in DOD wet iscontributions regions in is 0.12 80.3 combined and %. semi-arid This the and isthropogenic anthropogenic semi-wet, larger dust and contribution than plays arid the to an respective regions, anthropogenic natural revealing important dust that role events an- (suspended on dust, total blowinggions. dust dust, A and statistical because result dust the of storms) frequency Tablecombined is 1 semi-arid of lower suggests in and that total wet semi-wet anthropogenic re- regions dustdust aerosols contribute from 52.5 aerosol % the over to the alldust total three emissions anthropogenic over regions. semi-wet The andtivity more semi-arid and may poor frequent be ecological occurrence practices related of in to that anthropogenic the region. heavier human ac- 5 5 10 15 20 25 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | in North 2 − erent regions. To ff erent mass extinction ef- ciency in Eq. (1) that was ff ffi erent regions. What’s more, ff erence is mainly from the result of ff 10180 10179 erent continental regions reveals regional char- ff in India. Considering the mean DCB in four regions, the greatest 2 ects (Huang et al., 2006a, b, 2010, 2014; Li et al., 2011). − ff Supported by the National Basic Research Program of China We conducted a case-study to test our algorithm using CALIPSO data for the Takli- An analysis of sources over four di 111 project (No. B 13045).Data CALIPSO Center data (ASDC) have been a obtained NASAthe from Langley NASA the Research Earth Atmospheric Center. Observing Sciences The SystemActive MODIS Data Archive data and were Center Information obtained System,(EROS) (LP from Land Center. Processes DAAC) Distributed at the USGS Earth Resources Observation and Science Acknowledgement. (2012CB955301), National Sciences Foundation of China (41305026 & 41375032), the China the local anthropogenic dusts alsoand make human some health. contribution Therefore, it to istion local necessary among climate, to aerosol-cloud-precipitation air further processes quality, and investigatelocal the improve air regional the pollution interac- parameterization e of reduce this uncertainty, itficiency will for be the necessary natural to determine and di anthropogenic dusts from di China and natural dust over Africa.mainly Some farming, studies overgrazing, have and confirmed that waterpansion human usage, of activities, have dust likely been sources responsible inet for northern al., the 2007). China ex- Igarashi and et IndiaGong al. (Xuan (2011) et and add al. Sokolik, that 2002; drought (2004)percent has Prasad showed been in also that a China, although contributingemissions. it desertification factor. The has has relationship increased generated between by population disproportionatelyour only density four large and study a regions anthropogenic areas few further DCBdust of from supports mainly enhanced the comes dust above from results. cropland,mittent In urban, dry this and lake paper, pasture. anthropogenic basins Anthropogenicfrom is dust the not assumption from considered. of inter- A a single major value uncertainty for in mass these extinction e results comes used in this paper; this parameter probably varies between the di America to 0.42 gm makan and North China, known naturaltively. and From this anthropogenic dust we source found regions that respec- ratio anthropogenic dust that has is a less layer-integrated depolarization than that for natural dust. This di burden of anthropogenic dust occurs overoccurs India over and Africa. the greatest On burden a of natural percentage dust basis, anthropogenic dust is greatest over East (Huang, 2006a, 2010), anthropogenic(Huang carbon et al., dioxide 2011), emission, and snow landfected use by albedo climate change change variability (Sokolik and et in al.,(Ginoux turn 2011). can Dust et impact emissions climate, are al., air af- quality, 2012).pogenic and human aerosols Global health (agricultural dust dust, aerosolsaerosols), industrial but not black also only carbon, include containanthropogenic natural and activities locally dust other could from emitted, anthropogenic deserts. account anthro- that Dust for has been emissions a quantified that large but result withper, proportion we large from have uncertainty of developed (Sokolik global an and algorithm dustmeasurements Toon, 1996). to and emission In detect this anthropogenic the pa- dust MODIS basedthropogenic land on dust CALIPSO cover to dataset. the total From global this, dust the load contribution was determined. of an- acteristics. Annual mean anthropogenic DCB value varies from 0.12 gm anthropogenic dust produced by human activitiesaerosols being within generally mixed the with PBL, other type are thus some being misclassifications more that spherical9.6 should than % be natural of kept dust. anthropogenic in However, dust mindis there is for misidentified misclassified the as as results. anthropogenic natural Approximately aerosol dust dust due and to within 8.7 human % the25 activity, of % PBL. such natural contribution The as dust to agriculture local themainly and anthropogenic global come industrial dust continent activity, from accounts dust semi-aridtotal for load. anthropogenic and The dust semi-wet aerosols. anthropogenic region, dust occupying aerosols more than 52 % to the 5 5 25 20 15 10 10 25 20 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ect ff ects of dust aerosols ff ect on cloud water path over East Asia, ff 10182 10181 ective number concentration of water clouds over ff Geophys. 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Academic, B.: Dordrecht, Meteorology 666 for ScientistsTegen, I. and Engineers, and Brooks/Cole, Fung, Pacific I.: Grove, Calif., Contribution 2000. to the atmospheric mineral aerosol load from land surface 5 5 10 15 20 15 30 10 20 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 2 − Mean ADCB (gm Contribution to regional DOD (%) DCB (Tg) (63.0)(70.2) 0.17 0.42 (54.0)(21.5) 0.09 0.26 (%) 6 6 6 6 2 10 10 10 10 × × × × Anthropogenic area km Anthropogenic DCB (Tg) 2.48(41.2)3.16(52.5)0.38(6.3) 3.09 4.67 80.3 0.56 67.7 67.9 N 3.71 N 5.56 ◦ ◦ N 1.98 N 3.40 ◦ ◦ 7 7 6 10 10 10 10188 10187 × × × ) 2 Latitude Range Area (km E 0.0–30.0 E 25.0–50.0 ◦ ◦ W 20.0–50.0 ◦ E 5.0–27.5 ◦ anthro- pogenic DOD W–35.0 ◦ Range Summary of anthropogenic dust annual mean statistics by climate region. Anthro- Description of dust study areas. Latitude and longitude ranges; area and percent of RegionWetSemi-arid and semi-wetArid Mean 0.07 2.46 0.12 0.06 1.77 1.21 East China 100.0–130.0 Region Longitude IndiaNorth America 135.0–65.0 60.0–90.0 North Africa 20.0 the region considered to contributepogenic to dust anthropogenic column dust burden emissions; (ADCB) and of annual the mean regions anthro- considered in this study. Table 2. Table 1. pogenic dust optical depthburden (ADOD); (DCB) (and total percent regionalpercent contribution area; contribution by to regional regional region); anthropogenic DOD. regional dust dust column column burden (DCB); and Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 10190 10189 A conceptual schematic for sources and transport of dusts upon which the detec- Global distribution of the land cover types for anthropogenic dust source types (in- cluding urban, cropland andblack grasslands) rectangles retrieved denote by four combing majors MODISand source and Africa. regions GRUMP studied: data. East The China, India, North America, Figure 2. tion process ofatmosphere; anthropogenic the dust arrow and is red based. wavy lines The represent yellow lifting dots and turbulence, represent respectively. dust aerosol in the Figure 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | and the layer- 0 δ . 1 − for North China and Taklimakan from the entire 0 γ 10192 10191 cient ffi , respectively. The color of each pixel represents the frequency box measuring 0.01-by-0.001 sr (b) 0 γ ∆ − 0 δ ∆ Flow chart of anthropogenic dust detection by combing CALIPSO and land cover The relationship between the layer-integrated depolarization ratio and within the PBL (a) dataset provided MODIS. Figure 4. of occurrence for a profile Figure 3. integrated attenuated backscatter coe Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 10194 10193 Global distributions of seasonal mean for total dust optical depth derived from Global distribution of seasonal mean for anthropogenic dust column burden from 2007 through 2010. Figure 6. Figure 5. CALIPSO measurements from 2007 through 2010. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . 1 − 10196 10195 Global distribution of the percentage of anthropogenic dust within the total dust col- Comparisons of dust column burden over four seasons as a function of climatological mean precipitation. The precipitation interval is 100 mmyr Figure 8. umn burden. Figure 7. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | North America, (c) India, (b) East China, (a) 10198 10197 Comparison of the relative contribution of mean anthropogenic (red) and natural Regional distribution of annual mean anthropogenic dust column burden derived from North Africa. (d) (blue) dust column burdens in four geographical regions. Figure 10. Figure 9. CALIPSO measurements (2007 through 2010)and for