Origin and Radiative Forcing of Black Carbon Transported to the Himalayas and Tibetan Plateau

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , and 5 Chemistry and Physics Discussions ect at about 5– Atmospheric ff , D. K. Henze 4 airs, Princeton University, Princeton, ff , E. M. Leibensperger 3 21616 21615 , J. Wang 1,2 orts to slow the rate of glacial melt by identifying regions ff ect, and with significant seasonal variation in the northern Tibetan Plateau. , D. L. Mauzerall 1 ff within the region, an order of magnitude larger than radiative forcing due to 6 2 − and Physics (ACP). Please refer to the corresponding final paper in ACP if available. This discussion paper is/has been under review for the journal Atmospheric Chemistry Woodrow Wilson School of Public and International A Department of Civil and EnvironmentalDepartment Engineering, Princeton of University, Earth Princeton, and NJ, Atmospheric USA Sciences, University of Nebraska-Lincoln,School Lincoln, of Engineering and AppliedMechanical Science, Engineering Harvard Department, University, Cambridge, University MA, ofComputer USA Colorado-Boulder, Science Boulder, CA, Department, USA Virginia Polytechnic University, Blacksburg, VA, USA – Published: 13 September 2010 15 W m the direct e Radiative forcing from reduced snowcan albedo help accelerates inform glacier mitigation melting. e that Our make analysis thePlateau. largest contributions to BC deposition in the Himalayas and Tibetan other countries. Theand magnitude receptor of location. contribution We fromMiddle find that each Eastern sources region fossil as fuel varies variedthe combustion with as Himalayas and can African season Tibetan biomass significantly Plateau. burningregions contribute We and and compute to estimate radiative the the forcing in forcing BC due the reaching to snow-covered the BC induced snow-albedo e location from which BCPlateau arriving originates. at a We then variety calculateanalyze of its the locations direct seasonal in and variation the snow-albedo inwhich Himalayas radiative the and provides forcing. origin Tibetan a We of detailed BCblack map using carbon an of concentrations adjoint the at sensitivity receptor locationern analysis, locations. of India We emissions and find that centralthe that directly China emissions precise contribute contribute from location to the north- varies majoritywestern with and of season. central BC China, The as to Tibetan well the as Plateau Himalayas, from receives although India, most Nepal, the BC Middle from East, Pakistan and The remote and high(BC) elevation regions emissions of from central aglaciers Asia and are variety questions influenced of exist, by of locations.BC both black reaching scientific carbon and the BC policy glaciers. deposition interest, We as use contributes to the the to adjoint origin of melting of the the of GEOS-Chem model to identify the Abstract 1 K. Singh NJ, USA 2 3 NE, USA 4 5 6 Received: 1 September 2010 – Accepted: 3 September 2010 Correspondence to: M. Kopacz ([email protected]) Published by Copernicus Publications on behalf of the European Geosciences Union. Origin and radiative forcing ofcarbon black transported to the HimalayasTibetan and Plateau M. Kopacz Atmos. Chem. Phys. Discuss., 10,www.atmos-chem-phys-discuss.net/10/21615/2010/ 21615–21651, 2010 doi:10.5194/acpd-10-21615-2010 © Author(s) 2010. CC Attribution 3.0 License. 5 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 − ect of BC 20 W m ff + ect). Scattering ects and source ff ff ect on the lifetime ff erent measurement ff (Hansen et al., 2005) 2 − ects on clouds (semi-direct ff in the atmosphere, BC results 2 0.05 W m + (particulate matter with an aerodynamic di- 5 . cacy of radiative forcing due to BC deposition 2 21618 21617 ect alone is ffi ff culties contribute to a mix of model underestimates ffi has been shown to increase the rate of cardiopulmonary 5 . 2 (Koch et al., 2009b; Kopp and Mauzerall, 2010). The most re- 2 − ects) add large uncertainties to both BC concentrations and radiative 1 W m ff + 0.02– + The Himalayas and the Tibetan Plateau, also collectively known as the Third Pole, Modeling global transport and radiative forcing of BC poses numerous challenges. an adjoint model approach that improves on both of these by providing both the exact represent a large areaby of growing seasonal emissions and of permanent Asianshow snow a air cover. rapidly pollutants, increasing They and trend are (Xu observationsconcentrations et surrounded of in al., BC 2009a). the content Here snow-covered we inwhere regions connect snow observations to the of the BC BC surrounding atalbedo emissions RF the by of Third tracking BC in PoleSeveral the originates. studies snow-covered parts attempted of We theglacier to also Himalayas region and calculate quantify the through the the Tibetan aand Plateau. direct Carmichael, sources mix and 2008) of that and snow- back forward contribute trajectory modeling modeling BC (Ming (Menon et to et al., 2008, the al., 2009). 2010; Asian We use Ramanathan (Flanner et al., 2007). Inon addition, snow the is e estimated toamount be of 236% radiative (Hansen forcing et fromin al., 2.36 BC 2005). times on This the snow means temperature that and change. for CO the same forcing (Allen and Sherwood, 2010;with Bauer which et to al., evaluate 2010).techniques the (thermal Finally, models vs. measurements thermal of are optical)(Vignati BC limited may et and result al., in the 2010). variationand use All in overestimates these of measured of di observations quantities di as well(RF), as a large range forcent BC total global radiative estimate forcing of snow-albedowith e spring estimates in parts of the Tibetan Plateau reaching as high as and thus transporttransformation of is BC only (Liu startingample, et to be only al., incorporated 5 2010) in outet and models al., of (Liu incorporation 2009b). the et of Complicated al., 17and cloud the 2010). AEROCOM indirect microphysics physics models For and e of ex- include BC e that physical aging of BC (Koch from the hydrophobic to hydrophilic form of BC can have a large e highly uncertain (Bond et al., 2004, 2007; Shindell et al., 2008). The conversion rate forcing in addition to those withgeous clear (Koch impacts et on al., public 2007). health wouldon BC clearly definitely snow be has advanta- and a lowers positive radiative snowthat forcing albedo deposits when in it on deposits the snow Asian andRamanathan and glaciers, ice Carmichael, the can 2008). Arctic accelerate In and meltingon fact, (Hansen elsewhere. snow nearly decreases and BC all snow Nazarenko, particulate albedo 2004; of matter (Flanner BC that et can deposits al., be 2009) of and wider thus relevance estimating (Unger the et impact al.,Past, 2010). present and future emissions of aerosols in general and BC in particular are warming (Aunan et al., 2009;all Bauer et (2010) al., performed 2010; a Chen metaBC et emissions analysis al., from 2010). reconciling contained recent combustion Kopp result and estimatesis in Mauzer- a and positive low radiative concluded probability forcing, that that while carbonaceous there itive aerosols radiative from forcing. open Targeting biomass mitigation burning strategies have to a sources pos- with a positive radiative Previous studies (Koch etCarmichael, al., 2008) estimated 2009b; radiative Koppneither forcing and straight (RF) contributed Mauzerall, forward by nor 2010;types BC, the Ramanathan are but warming the and included task potential (direct,aerosols is clear are indirect, co-emitted when with semi-direct all blackincrease and carbon e the and snow-albedo positive have RF a e of negativeon BC RF when clouds in internally could isolation mixed be but with may duction warming BC. The of or indirect BC cooling. e emissions In might not fact, necessarily several recent result studies in cooling argued and that could re- even lead to Black carbon (BC) is a componentameter of 2.5 µm PM or less).disease PM and premature mortality (Poperadiation et and al., thus 2002). is BC potentially is a also warming a agent powerful in absorber the of atmosphere (Jacobson, 2001). 1 Introduction 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ), (1) ) in the at- y ) by emissions K ). The resulting units y http://geos-chem.org/ in Eq. (1) below and is a K 1 degrees and 48 vertical layers × cient computation of source-receptor ffi 21620 21619 longitude receptor grid box, we compute the emission con- × 2.5 degrees and 30 vertical layers. Over the past several years, GEOS-Chem x × K 2.5 degree latitude The GEOS-Chem adjoint model provides e We use the Bond et al. (2004) global BC emissions inventory with 8 Tg global an- Our goals in this paper are thus to: (1) provide a spatially and seasonally resolved ) yields an estimate of how much BC emissions from each model grid box con- = × x 2 tributions within the column over the course of a two week simulation. To assess the y As the BC model( simulation is linear, multiplicationtribute of to the concentrations sensitivity and ( depositionare in thus a units receptor gridof of box our mass ( simulations. andin can We snow be select and averaged, five receptor glaciers as grid exist we boxes, (as do for seen here, which in over BC Fig. the measurements time 1 period and discussed in Sect. 3). For each lution at a particularadjoint site model (Henze as et amospheric al., tool column to 2009; above a compute Zhang certain theto et model sensitivity global grid al., box, of emissions 2009). including BC of theunitless concentrations BC. Here fraction quantity. that ( This we deposits, sensitivity use is the denoted as days (Park et al., 2005). We31 simulate December BC 2001, concentrations following and several deposition monthsa for of strong 1 spin-up. January north – Year Atlantic 2001 Oscillation was a (NAO) year signal. without sensitivities (Henze et al., 2007).CTM. It The is adjoint derived has from beenof the developed aerosol GEOS-Chem and (Bey previously (Henze et used et al.,2010; to 2001) al., Kopacz estimate et the 2009) al., magnitude and 2009) and CO to sources compute local, (Henze upwind et and al., chemical sources 2007; of Kopacz pol- et al., nual emissions, of which 38%open comes burning. from fossil We fuel,emissions overwrite 20% from the from the biofuel emissions GFED2 and from inventorydrophobic 42% (van and open from der hydrophilic burning states Werf with in et a biomass al., 4:1 2006). burning ratio, with BC a is conversion emitted time in constant hy- of 1.15 transport of pollution to the Third Pole. atively coarse resolution cannot provide detailedTibetan information of Plateau the transport, intra Himalayan GEOS-Chem and can illuminate regional and inter-continental GEOS-Chem is awhich global solves the chemicalassimilated continuity transport meteorology equation from model in NASA/GMAO. (CTM) Hereteorological individual fields, we ( model which use have grid a v8-02-03 nativefrom with boxes. resolution the GEOS4 of surface 1 me- to It 0.01 hPa. isto For 2 computational driven expediency, we by degrade thehas resolution been used extensively and(Fisher et successfully al., to 2010; study Heald et long al., range 2003; transport Li et of al., pollution 2002; Zhang et al., 2008). While the rel- 2 Models 2.1 GEOS-Chem global Chemical Transport Model (CTM) and its adjoint both climate and localmodel and air a quality. four-stream broadbandof In radiative BC transfer our and model its study, associated to we RF,we respectively. characterize In employ the evaluate Sect. the origin the 2, model we GEOS-Chem describe BCsnow the adjoint surface measurements; models, concentrations in in Sect. with 3 Sect.discuss available the ice 4, BC core contributions we and from analyzeadjoint surface various model; regions radiative to we forcing the conclude third results; infocused pole Sect. on in as 6. the calculated Sect. Third by This Pole. 5 the is the we first adjoint receptor modeling study each grid box that arrived at the receptor grid box. estimate of the origin ofdue BC arriving to at the BC Thirdsuggest at Pole; and target the (2) areas estimate Third radiative for forcing Pole. BC mitigation Identifying that the have regions the largest from potential which co-benefits BC for originates will location (model grid box) from which BC is emitted and the quantity of emissions from 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3% when < erences of ff . In the remote regions of 2 erence between upwelling ra- ff erence between the four-stream ff http://wiki.seas.harvard.edu/geos-chem/ 21622 21621 ) and in the Arctic using data from NASA’s Arctic 1 ). Adjoint ects of internal mixing on optical properties by doubling BC absorption. ff ects are carefully considered in the radiative transfer calculations (Wang et ff Leibensperger et al., in preparation Wang et al., in preparation 1 2 In this study, the radiative transfer calculation is conducted every 6 hours for the cor- betan Plateau using GEOS-Chem. To date,been GEOS-Chem evaluated BC over concentrations have the only UnitedVisual Environments States (IMPROVE) network using surface the measurementsprotected Interagency in national areas Monitoring parks (Park of and et Protected al., 2006; imate the e In addition to directthe radiative spectrally forcing, averaged we albedo computeWiscombe, changes snow-albedo 1985). due radiative to forcing BC from deposition on snow (Warren and 3 BC at the Third Pole:We simulated simulate vs. BC observed concentrations and deposition to snow in the Himalayas and the Ti- TAS) aircraft campaign during spring and summer of 2008 which can then be augmentedtimate by (Wang cloud et fraction al., to 2008). yieldindicated. Here, the we full The report sky clear-sky radiative model forcing radiative assumesestimate es- forcing unless external of otherwise mixing radiative of(Hansen forcing aerosols, which et of gives al., BC a 2005; that low-bound Jacobson, can 2001). be Following internally Hansen mixed et in al. real (2005), atmosphere we approx- Research of the Composition of the Troposphere from Aircraft and Satellites (ARC- diative fluxes with and without (BC) aerosols yields a clear sky direct radiative forcing, the Himalayas and thetopography and Tibetan meteorology. Plateau, As modelChem a evaluation cannot relatively is resolve coarse criticalflow individual resolution due within global mountain to model, them. peaks complex GEOS- GEOS-Chem and We and valleys thus its or do adjoint’stransport the not documented of attempt complicated ability pollution, to to air as resolve accurately mentioned represent such in long flow, Sect. focusing range 2. instead on As can be seen from maps of emis- profiles (of water vapor, temperature,of BC and are pressure). adopted from The Wang and single Martin scattering (2007). properties The di for the computations oflated solar values irradiance are covering within theal., 5%, 1988). entire when Previous SW studies compared spectrum, showobserved to the downward an shortwave adding-doubling excellent calcu- irradiance agreement calculations at between the (Liouaerosol the surface, e with et calculated di and al., 2004). responding GEOS-Chem simulated 3-D aerosol distributions and GMAO’s atmospheric diative forcing of aerosols, suchet as al., smoke 2004), (Wang and andpor Christopher, sulfate 2006), particles absorption dust (Wang and (Wang et Rayleighcalculation al., scattering 2008). also uses are The the gas included2003). absorption, monthly in water mean For the va- surface the modeland reflectance principal calculations. line-by-line data atmospheric irradiance (Koelemeijer The gases, calculations et the is al., di within 0.05% (Fu and Liou, 1993). Overall, 2.2 Radiative Transfer Model (RTM) A four-stream radiative transfer modelings is respectively used to of compute theby the atmospheric the top-of-atmosphere forc- BC deposition and ofmodel, the originally BC. designed change The to of modelcloudy calculate surface is conditions the (Fu albedo a atmospheric and radiative induced plane-parallel Liou, transfer broadband in 1993), radiative clear which and transfer was later modified for calculation of ra- cation, across four seasons:soon/summer (July), dry/winter post-monsoon/fall (October). (January),weeks Each pre-monsoon/spring of simulation (April), the spans corresponding mon- the month firstcently in updated two 2001. v8 Our of the simulations GEOS-Chem areindex.php/GEOS-Chem adjoint performed ( with the re- seasonality of these contributions, we perform four simulations for each receptor lo- 5 5 15 10 20 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | E, in the same ◦ N, 89 ◦ ect of snow aging. Table 1 shows ff 2.5 degrees, and chosen due to the × during the summer in the north and north- 1 − 21624 21623 in summer surface snow in Namunani (western 1 − and 446 µg kg 1 − ected by the monsoon circulation and located on the western edge of the ff We sample the eastern Himalayas with a model grid box that contains East Rongbuk In order to identify and quantify the variety of regional and seasonal sources of BC Here we use BC measurements in precipitation and surface snow to evaluate the indicates a mix of good agreement (during summer in the east), model underestimate experienced a 3.5 fold increaseMeikuang in glacier deposited (NE Tibetean BC Plateau) from withand 1998 very potential to high, influence 2005 partially from (Xu local, China et depositionTibetan to of al., Plateau), BC its 2009a); east; not andglaciers on Miao’ergou beyond glacier the the (center Third Tibetan northern Pole. Plateau itself, andglacier thus (which an starts extension from Mt. tomodel Everest grid Asian or box). Qomolangma Several BC Peak,Comparison 28 observations are of available GEOS-Chem in the simulated Himalayas BC (see Table with 1). available BC concentrations in snow BC reaches the Himalayasinclude and a Tibetan Plateau glacier (Ming atluted et part the al., of foot 2008, the offlow 2009). Himalayas; not Mt. Mt. The a Everest Muztagh sites (EverestTibetan glacier site), Plateau (NW (Xu in Tibetan et the Plateau) al., eastern, representing 2006); more Zuoqiupu pol- glacier (SE Tibetan Plateau), which has the remote mountains. to this remote snow-covered partFig. 1), of Asia, each we oneavailability focus model of on grid 5 observational box receptor datagions in locations represent from size, (shown five the in i.e. glaciers glacier where 2 potentially BC sites accelerating deposition snow mentioned (dry melt and above. (Flanner2008). wet) et impacts al., These Together snow 2009; the re- albedo, Ramanathan five and Carmichael, sites are influenced by distinct transport pathways by which et al., 2010).soon We (non-monsoon) season, find generally that, May–Octoberconcentrations in (November–April). here Although fact, depend the on BC bothson deposition the amount for is of lower low BC BC and (high)aerosols precipitation, concentrations are throughout the during scavenged likely the close rea- the mon- to monsoon source is regions. As that a during result, the less BC rainy is season transported to tions has been previously reported both in snow (Ming et al., 2009) and air (Marinoni which the global model does not capture. Large seasonal variation in BC concentra- eastern Tibetan Plateau. BCof concentration 2–3 in lower snow during on thevations the across monsoon Tibetan than seasons Plateau during are iscould the available. a conceivably non-monsoon factor be Thus higher season the if where pre-monsoon highestGenerally, obser- observations the concentrations for model these reported identifies sites here were the available. across seasonal and the spatial diverse region, variation of butover-estimates the the ranging concentrations individual from data 10% point totions comparisons a reveal are factor under- Meikuang of and and 3concentrations. with La’nong, These no where sites systematic neighbor observations bias. local indicate sources Two excep- exceptionally (Ming high et al., BC 2009; Xu et al., 2006) at all times, neglectingthe the comparison potentially between significant simulated and e Pole. observed BC content There in is snowson, across a from the the Third large low variation valueHimalayas), to in of 111 0.3 measured µg µg kg kg concentrations with location and sea- ability of GEOS-Chem tobetan simulate Plateau. BC The content observationsspan in (Ming several years the et (and snow al., seasons) andafter 2008, of we 2009; the 1990. limit Xu our Himalayas et comparison andability Model-data to al., Ti- to those 2006, comparison simulate taken 2009a, BC or in concentrations dated b) ical in this data the case snow, in but evaluates correctly alsoquantity the estimating not accuracy here the only of is amount meteorolog- GEOS-Chem’s and theprecipitation. timing ratio of of We precipitation. the assume total The that modeled amount this of approximates BC BC deposited concentration to in the surface total snow amount of and surface concentrations of BCcan are be near densely transported populated tothis regions, BC the from transport which Third and BC deposition Pole.concentrations accurately, to we To available compare observations. evaluate GEOS-Chem’s simulated GEOS-Chem’s BC ability to simulate sions, surface concentrations, and wind patterns (Figs. 2 and 3), the largest sources 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) 1 − , and 1 − erence high- ff are the second and 67.3 µg kg respectively. The 1 − 1 1 E). The model com- − − ◦ ). Model-measurement 1 − N, 75 ◦ ected by glacier melt. Xu et ff measured during the summer is 1 − and 46.3 µg kg 1 − E). We chose this site due to the large during monsoon and non-monsoon sea- and 15.0 µg kg ◦ 1 1 − − E) site north of the Tibetan Plateau, in the ◦ N, 94 21626 21625 ◦ in the model). This concentration di N, 94 1 ◦ − E). The limited model comparison with available data in- and 11.3 µg kg simulated by the model. The seasonal cycle of BC in the ◦ 1 1 − − (15.1 µg kg N, 97 1 ◦ − In addition to the sites strictly in the Himalayas and the Tibetan Plateau, we also We examine a region of the western Tibetan Plateau using a model grid box that We examine a region in the northeastern Tibetan Plateau with a model grid box We sample the southeastern Tibetan Plateau with a model grid box that contains select the Miao’ergou glacierTienshan Mountains (43 (Ming etthe al., largest 2009). amounts This of siteemissions BC has contribute in been significantly the found (Ming Asian toand glaciers et contain region and al., some allows it of 2009). us isPlateau to hypothesized In are assess that addition, impacted to European examining by whatare this global extent BC site within the emissions. 15% Asian Simulatedhighest glaciers of of BC outside the the concentrations the sites observations in Tibetan studied. snow at the site, and at 94.5 µg kg larger than the 16.7 µgmodel kg is consistent with2006), observations and indicates of concentrations the duringin seasonal the other cycle summer seasons. that at are other half sites as large (Xu as et those al., inaccuracies in emission inventories,and uncertainties location, in as precipitation well frequency, asconcentrations amount that BC are aging. not However, influenced givenalso by the represents local model’s background sources, ability concentrations it to successfully appears (Park likely represent that et BC the al., model 2005). contains the Mt. Muztaghparison glacier with in available surface the snow concentrations Pamirsnow is Range most complicated, (38 since likely the underwent measured aging. The 37.2 µg kg centrations are unusually largeglacier is (Table 18.2 1). µg kg lights The an important concentration question at ofair the nearby above role Dongkemati of and local to versus theuncertainties, distant snow contributions including to of model BC the transport in glaciers. in the a Complicating topographically the complex picture region, are potential several model comparison at a nearby glacier confirms that Meikuang, Zhadang and La’nong con- are not captured by the model (15.0 µg kg transport and precipitation more than emissions. that contains the MeikuangBC glacier (36 concentrations indue surface to snow its reported location:low by and the Xu Yangtze central-northeastern et riversal. Tibetan (2006) al. which Plateau, report (2006), the could near possibilitythe 446 the potentially of µg Meikuang kg nearby origin site. be coal of Similarly, containing a relativelyters rock Yel- high strata on concentrations contributing the near BC Plateau major to at population cen- Zhadang and La’nong glaciers (87.4 µg kg that BC deposited in Zuoqiupu(Xu glacier et has al., increased 2009a). by However, athan by factor 2005, the of observed modeled 3.5 BC during ones: snowlower that concentrations during time a are the still factor monsoon. lower of Sinceis two the intended emission lower to inventory represent during used the non-monsoon here mid-1990s, this (Bond season mismatch et and could al., result third 2004) from errors in model Zuoqiupu glacier (29 dicates a model overestimatemonsoon of and deposition a factor incentrations of the were 4 5.1 region µg during kg by non-monsoonsons, a seasons. while factor In the of 2001, model 2model the estimate does during ice was capture the core 13.3 the µg con- the kg observed monsoon to factor non-monsoon of season. 2–3 Measurements spanning increase 1998 in to 2005 snow indicate concentration from east and during summer ining the from west), with west observed to concentrations east.Mt. generally Everest decreas- Both grid model box and duringshows measurements the that find monsoon lower air season BC concentrations thansurface deposition are at air in other also measurements the times confirm lower of that during year. seasonality the (Marinoni Figure monsoon et 2 al., season 2010). and recent (during summer in the east) and overestimate (during the post-monsoon season in the 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 2 − − ra- be- 3.78 0.5– 2 ects. 2 ected − ff + + − ff 2.0 W m 0.85 W m + + 20 W m + 1.74 W m 1.0– + + ect, are consistent ff , after the adjustment. 2 for all-sky condition (af- − 0.19 to ect clearly dominates the . Thus our assumptions 2 ff 1 + − − 3.47 W m + 0.16 W m + for a particular site, after two days of 1 N. This seasonality has potential conse- − ◦ 0.39 to in the eastern Himalayas during the summer, + –35 ect in the Tibetan Plateau during the spring, ect. 21628 21627 ◦ 2 ff ff − , is slightly higher than the latest AeroCom’s average 2 , respectively. The estimate with all-sky and internal − 4.5 W m 2 − + ects in five model grid boxes containing the five glacier sites. ff 0.32 W m + for clear-sky condition and 0.32 W m + 2 − ects, we use the RTM described in Sect. 2 and our GEOS-Chem (Kopp and Mauzerall, 2010). To compute monthly mean snow albedo ect are more varied. Over India, Menon et al. (2010) find (Koch et al., 2009b) and also higher than recent meta-analysis estimate ff , with lowest and highest values found at the northernmost site during ff 2 2 2 and − − − before it is doubled to adjust for internal mixing, and 2 − 2 − 0.36 W m + 15.6 W m 0.22 W m 0.25 W m + + + Our radiative forcing numbers, especially for the snow albedo e Figure 4 shows the seasonal cycle of instantaneous radiative forcing due to BC di- 1.0 W m 0.72 W m the BC direct e ing and snow melt areassess the beyond climatic the impact scope of ofthe the snow-covered this radiative areas forcing study. in here, In our thedirect conclusion, calculations Third suggest Pole radiative while the that forcing we snow-albedo signal in do e and not likely enhances glacial melting rates. with results of previousdiative studies. forcing Flanner from et theand al. snow-albedo Ming (2007) et e al. estimates (2008) upwhich report to are both within the range of our estimates. The values for radiative forcing due to quences for increased snow melt.an Our high increased radiative rate forcing values oftion in summer glacier and suggest and potentially a highto melting altitude reduce season melting glacial that in melting, extendsother summer it seasons. into might due spring However, be formal to and calculations as BC fall. of crucial deposi- the to Thus connection focus in between on radiative order forc- summer emissions as on Radiative forcing due toto snow albedo change iswinter much and larger summer, and respectively.exhibit ranges a from weaker Lower seasonal latitude cycle.alone sites do Meanwhile, not of our exhibit Mt. significant calculationsyear. seasonality of Everest with snow We most and albedo values thus Zuoqiupu change around concludeseasonal 6% changes throughout that in the the solar irradiance. seasonalityalso While in find expected at radiative a high forcing strong latitudes is seasonal of the due signal Arctic, at largely we 30 to the sider in this study correspond toclear-sky glaciers direct and radiative hence forcing are due snow-covered+ year to round. BC The for allafter. glacier sites The is corresponding typically fullfore about the range internal of mixing the adjustment, direct and forcing is representative of the snow covered areas within the grid box. The five sites we con- snow albedo forcing is not necessarily uniform over the entire grid box. Rather, it is cle accumulation during snowby melting. aerosol deposition, Meanwhile, can(Flanner result aging and in of Zender, a 2006). snow changecentrations In alone, in addition, in una albedo Xu of fresh et up snow al.surface to (2006) average melting 0.12 observed 6.6 they µg after that kg two while increasedlikely BC weeks underestimate and con- the snow measured albedo 52.6 e µg kg rect and snow-albedo e Although we report both forcing numbers for each grid box examined, the calculated Chem simulations with a previously establishedin relationship snow between and BC ice mass and fraction A a similar spectrally relationship averaged was change previouslyKoch in employed et snow by al. albedo Hansen (2009a). (Ming and(wet et Nazarenko We (2004) al., and compute and 2009). BC dry mass deposition) fraction to as total the precipitation. ratio of We total thus deposited BC neglect snow aging or parti- derived albedo changes.ing Our is global annualter mean direct multiplying (external by mixing+ cloud only) fraction). forc- mixing adjustments, Correcting forof internal mixing ofof BC, this yields change due to BC deposition we use the quantities of BC deposited in our GEOS- We compute radiative forcing ofFollowing Kopp BC and resulting Mauzerall from (2010)the its and referenced direct impact studies and of therein, snowBC. non-resolved we albedo approximate internal For e mixing both of e aerosols by doubling the direct RF of 4 Radiative forcing due to BC in the Third Pole 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ciency than ffi ect. using Beig emissions ff quantity in Eq. (1). Ad- 2 − x . We quantify and report 1 K − day 2 − 1.37 W m + 21630 21629 erent BC source regions to the Third Pole. Our analysis ff cult due to the coarse resolution of the model. The Himalayas span at most ffi ecting water resources. This is the first study that attempts to identify the mag- ff Detailed maps of the origin of BC transported to each air column (Fig. 5) reveal emis- The most striking result of our study is the spatial extent of BC source regions that the year, the attribution of localtry and is regional di Himalayan emissions to a particular coun- site. Our resultstions, underscore but not also only the need potential for locations reducing to emission inventory prioritize5.1 uncertainties. emission reduc- Origin of BC reaching theFigure Himalayas 3 (East shows Rongbuk the glacier) variabilityrection in at BC the emissions surface seasonally and withfrom wind at India, magnitude China 500 mb and and overlaid. Nepal di- Everest deliver Our site, about simulations on 91% indicate of average BC about that in 15, emissions the 12 atmospheric and column 10 at tonnes the per day respectively. Throughout (see Table 2) country levelwithin contributions, countries but is note important that and regionalseasonal can and breakdown be seasonal of seen variation contributions in the atbers figures. Mt. are In Everest subject addition, and to Table Mt. 3assessment numerous Muztagh shows of uncertainties sites. the and The relative should num- importance be of used regional only for BC a contributions qualitative to each receptor the Everest grid box, althoughlarger, the resulting fraction from deposited at lower that precipitation site at is Miao’ergou about than a at factor Everest. sion of hot five spots andof seasonal BC variations within in countries. theall air These grid column maps boxes. above show In each short, sensitivity ditionally, glacier all they maps are and are emission at averaged contributions, the over the the the glacier area two surface weeks of to of the the emissions grid simulation in window box. and Hence, over the units are µg km Nepal and the Middle East. Themuch GEOS-Chem BC adjoint is model transported indicates to thatas the 3–4 at atmospheric times the column as sites at the ingrid Mt. the Everest box Tibetan receptor tends Plateau. grid to However, box the beMiao’ergou observed less, site deposition and atmospheric in the the column, model Everest for generally example, overestimates receives that about deposition. half as The much BC as Third Pole is emitted in India and China, with substantial seasonal contributions from son. The dominant sources changethe with Third season Pole. and vary However, with the receptor overwhelming location within majority of BC that is transported to the the forward model approach (Ramanathantrajectory and Carmichael, approach 2008). (Ming Also, et unliketor al., a site, back 2009), the which adjoint onlyemissions calculates in tracks the each air quantity grid mass of box flow in BC to the contributed global the to model. recep- theimpact receptor the Third site Pole from andally. how Meanwhile, the there contribution of is those nobiomass source seasonal burning. regions variability varies in season- Figure BCabove emission 5 (and inventories, partly shows except deposits the for on) the locations five from glaciers shown which in BC Fig. that 1 originates reaches in the each sea- air nitude of contributions from di indicates where future emissionand reductions might glacier be melt. mostthe helpful As source in regions a slowing contributing first warming glaciers. BC step, transported The we to adjoint use the approach atmospheric the allows column GEOS-Chem for above adjoint much five greater model computational to e identify 5 Origin of BC at theThe Third origin Pole of BC atBC the (both Third source location Pole and is magnitude)icy inadequately at importance understood. the as Estimating Third the the Pole region isOf origin of provides of societal great water scientific importance for and a is pol- thus large the a proportion warming of Asian due population. to BC that will accelerate glacier melting, using the same Bond etinventory al. (Sahu (2004) et emissions, al., and are 2008). not directly Our comparable. valuesaveraged are In radiative only fact, forcing typically (Hansen for and global the Nazarenko,and model remote 2004), locations studies masking glacier of only regional regions high variability report and or globally low RF, especially for the snow-albedo e 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 21632 21631 erences in model-data agreement at those two sites are due to transport and/or ff via high altitude flow.receives There three is times a moreand strong BC April. seasonality pollution in Since during transport, in Julyis our and as due simulation to October Meikuang emissions changing than region meteorology. intions during In the from particular, January region relatively as do small seen source not inwest regions Fig. vary dominate (Middle 5c, seasonally, in the East this westerly and the contribu- northwesternChina first dominate China) half contributions to of during the the the year, second while half of large the sources year. from industrial eastern erlies, while duringcentral-eastern July China. and October Overallresponsible are in for primarily the approximately due 7.6 Meikuang tonnesabout to grid of half boundary box, BC that layer per emissions atday. flow day, from 3.2 emissions tonnes from China Emissions from per are Pakistan from dayemissions are Pakistan and are mostly arrive contributions transported at from in October India Meikuang from are throughout the 1.3 northernmost the tonnes part year, per of while the country Indian the di precipitation. 5.3 Origin of BC reaching theAs northeastern shown Tibetan Plateau in (Meikuang Tablebution glacier) 2 of and BC Fig. to theemissions, 5c, which Meikuang our during glacier model the is first results from half long-range indicate of transport that the of year the western are primary Chinese carried by contri- mid-tropospheric west- box receives emissions mainly fromday China from each), and with India smaller (about contributionsand 5 from tonnes Pakistan Nepal of (1.3 (0.6 tonnes), tonnes). emissions Bhutan per Everest, (0.7 The tonnes) the much similarity lower quantities ofBC of sources concentrations BC in for reaching the snow Zuoqiupu at two than Zuoqiupu sites, together and further the support model our overestimation conclusion of that box; other regions are relatively unimportant. On an annual mean basis, Zuoqiupu grid layer flow again allows for transportin from July south-eastern and China, October, rather south-eastern than India. Chinese emissions Thus, dominate in the Zuoqiupu grid 5.2 Origin of BC reaching theWind southeastern patterns Tibetan (Fig. Plateau 3) (Zuoqiupu andsimilar glacier) emission to contributions those at (Fig. Mt. 5) Everestality. at during In Zuoqiupu the January, are first most qualitatively half of of BCThe the comes mid-tropospheric year from flow and also the exhibit brings strong Himalayas BC and season- East. from southern In African Tibetan biomass April, Plateau. burning emissions anding from the the India Middle monsoon make season up (in halftropospheric July), of flow the from the Zuoqiupu south-eastern BC grid China arriving box in is at the under Zuoqiupu. east, the Dur- while influence in of October mid- the boundary and China contribute aboutDuring 75% of the monsoon post-monsoon BC seasonscolumn transported over (October), to Everest the grid the box majority EverestGanges comes grid from of Valley, similarly box. nearby BC to locations pre-monsoon in in season China, the (April). Nepal atmospheric and India’s Mauzerall, 2010), but thesignificant warming. fraction Thus that the travels contributiontropical of to approximately northern snow 1 tonne Africa covered ofonly BC regions is per contribute can significant, day a from result especially thirdNepal in as (30 of and nearby that 17 tonnes emissions in perChina from day January. on (12 Pakistan tonnes average) In and per to April,brings smaller day BC BC extent from from on comes south-western across average). southern mostly(13 and tonnes from southeastern In per India India day) and July, and and through the the from Bay monsoon southeastern of flow China Bengal (15 near tonnes the per day). surface Together India tion, and cut acrossseasonal India, and Nepal geographical and variability. China. Inately January, The BC adjacent contributions comes to from also the the exhibitflow Himalayas regions significant and also immedi- southern transports Tibetan BCAfrica Plateau. emits from The large African mid-tropospheric amounts biomass of burning. BC, which January typically do biomass not burning result in in warming (Kopp and two grid boxes in the north-south direction, about ten grid boxes in the west-east direc- 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | to ect 2 ff − 0.39 W m ected by some cult at our res- + ff ffi . 2 − , while monthly mean forcing 2 15.6 W m − + ected by BC from Pakistan and ff 3.78 to ected by them. Similarly to the glaciers 0.32 W m ff + + 21634 21633 ects of BC. GEOS-Chem generally represents the ff ect in the five glacier sites ranges from ff from some grid boxes in western China. It is di 1 − day 2 , with a global annual mean of − 2 − The most striking result of our study is the seasonal and spatial variation of sources 3.5 W m that contribute BC tocontributions the from Third northern Pole glaciers. India, Nepal We identify and large south-eastern comparable China emission to the Himalayas. the summer monsoon seasonestimates than of during simulated the BC rest arepart of found, the of but year. with the no Both mismatchand consistent under- to bias. precipitation and the We in over- attribute global this atforcing topographically model’s least due complex inability region. to to accurately BC+ Our represent direct monthly transport mean e radiative due to changes in snow-albedo ranges from We employed the GEOS-Chem model anding its the adjoint to Third analyze Pole. thefive origin We sites of estimated located BC the reach- throughout location thedue region. and to magnitude In direct addition, of we and emissionsspatial computed that and snow-albedo the seasonal a e radiative variation forcing of BC content in snow, with lower concentrations during indicating that while biomassbetan burning Plateau, emissions northern from Asianon Russia glaciers the might are not Tibetan a reach Plateau,the the Miao’ergou Middle Ti- is East, chronically atemissions a do an not average appear rate to of contribute significantly. 1.8 and 1 tonne per6 day, respectively. Indian Conclusions and discussion Chinese emissions versus 4.3–13.4 tonnestion that in comes other from months. Russianlargely biomass During to burning spring, the is contribu- spring comparablebiomass to agricultural burning that burning emissions from contribute and China. 5.3sons. summer Due and This boreal Russian 1.5 tonnes forest biomass of burning burning, contribution BC Russian is per unique day in in the those glaciers sea- we consider, emissions from eastern China dominate with almost 39 tonnes per day arriving from site throughout the year,with at an the annual rate average contribution of from about China 4 about tonnes 15.3 per tonnes per day day. from In some October, grid boxes, amount, either due to lowconditions, emissions or in both. the Bond et al. (2004) inventory, meteorological 5.5 Origin of BC reaching northAlthough of the the Miao’ergou Tibetan Plateau glacierof (Miao’ergou is glacier) the not same on emission theother regions Tibetan locations and Plateau, we meteorological it examined. conditionscates is that that As a transport emissions seen BC from in to north-western Table the 2 China and contribute substantially Fig. to 5, this the glacier adjoint model indi- Muztagh grid box receives BC2.7, from 3.9 Iran, and India, 5 tonnessions Pakistan make per and a day, China small respectively. at contributionand (much Meanwhile, the less outside rate the than of of 1 Middle tonne 1.5, April, perfrom East Indian day), China with contributing emis- China, in the Pakistan July). large Distant majority European of emissions BC do (up not to contribute 13 in tonnes any per significant day Another significant portion of BCtropospheric originates flow) in and the contributes Middle aboutEast East 1.9 tonnes (especially is of Iran not BC via per a mid- comparison, day, large even though emissions absolute Middle emission from sourceemissions China from according contribute Pakistan to and on the Indiatively. contribute average emission Together, about just inventory. 6.9 tonnes 2.4 four In and countries per 0.9BC (China, tonne day, at Iran, per Mt. while India day, Muztagh, respec- and with Pakistan)January 46% contribute contributions from 76% China are of alone. about Strong seasonality 25% in of transport the exists. annual total BC influx. In April, the Mt. The adjoint simulation indicatesfrom that the nearby majority regions of ofto BC western 10 that µg km China, arrives at Kyrgyzstan,olution Mt. Tajikistan to Muztagh and accurately is attribute Pakistan, the with origin up of emissions to a particular country, however. 5.4 Origin of BC reaching the western Tibetan Plateau (Mt. Muztagh glacier) 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects, Atmos. Chem. ff erent emission sectors ff ect and land-sea temperature ff orts to slow the rate of glacial melt by ff 21636 21635 erent global and high resolution regional mod- ff orts would have the largest benefits in preventing glacier melt. ff We thank the Geophysical Fluid Dynamics Laboratory for computational erent meteorological fields or di ff airs at Princeton University. D., Yantosca, R. M., Batchelor,S., R. Hyer, L., E. 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We are pleasedronmental to Policy (STEP) acknowledge funding programA from at the the Science, Woodrow Technology Wilson and School Envi- of Public and International ing di els, to test thecalculation robustness would of be our to results.rate compute the of A resulting snow climate temperature melt. extension(e.g. change of and our Disaggregation diesel the radiative of change transport, forcing in the residential contributions combustion of etc.) di to deposition of BC at the Third and where mitigation e These source regions are alsois places most where reducing critical. the uncertainty Inemissions in addition contributions BC to to emissions the thestudy recognized Third identified hot Pole spots (e.g. the northern of Middle(up both India East to overall and as 3 emissions central tonnes a and emissions China), per in substantial our day currently contributor in used to inventories. summer BC at in Mt. Asian Muztagh), glaciers despite not being a hot spot of ported and deposited inHimalayas. non-negligible Tibetan amounts Plateau (uptral glaciers to China, mostly about the receive 1 tonne Middle BCwith per East emitted season day) and in and in to western exact the somewhich location and extent of BC cen- India. the emissions glaciers. appear All to Our emission significantly study contributions contribute thus vary to identified warming regions over from the Third Pole Large dry season African biomass burning emissions, though far away, are trans- 5 5 25 30 20 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | cacy of climate forcings, J. Geophys. ˚ ag, A., Klimont, Z., Kondo, Y., Krol, M., ffi 21638 21637 precursor emissions using the adjoint of GEOS-Chem, Atmos. 5 . 2 ects on surface ozone in europe and north america, J. Geophys. 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C.: Black carbon (bc) Ming, J., Cachier, H., Xiao, C., Qin, D., Kang, S., Hou, S., and Xu, J.: Black carbon record Menon, S., Koch, D., Beig, G., Sahu, S., Fasullo, J., and Orlikowski, D.: Black carbon aerosols Marinoni, A., Cristofanelli, P., Laj, P., Duchi, R., Calzolari, F., Decesari, S., Sellegri, K., Vuiller- 5 5 30 25 20 15 30 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Himalayas 21642 21641 Tibetan Plateau 2005 non-monsoon 5.3–20.8 43.6 North of Tibetan Plateau Location Date Elev. MeasuredBC conc. Simulated BC conc. National origin of BC reaching the atmospheric column above the grid box containing Comparison of BC mass fraction in precipitation from GEOS-Chem and surface snow SiteMt. EverestZuoqiupu 12 500Meikuang 15 200 ChinaMt. Muztagh 5820Miao’ergou India 7600 6880 1000 5100 15 Pakistan 300 1270 10 500 Nepal 941 223 Middle East 558 3170 Russia 2380 1350 1840 321 122 3 3 5 225 433 1860 13 1000 471 142 7880 the foot of Mt. Everest) # Location name Lat Lon Elevation (m) year month (m) (µg/kg) (µg/kg) reference 1* East Rongbuk (at23 ERIC2002C4 Kangwure 28.05 Namunani 87.0 Qiangyong1* 6465 28.0 Zuoqiupu 87.02 28.5 20043 30.5 85.8 La’nong 28.3 65004 81.3 Qiyi 90.35 Zhadang 6000 106 Laohugou 2002 No.12 60807* 29.2 July 5400 1 glacier8 Meikuang 96.9 2001 summer9* 6465 2001 Dongkemadi 2001 30.4 39.4 Mt. Muztagh summer 5600 6500 90.6 96.6 summer 30.41 summer 39.2 39.0 6000 90.52* 1998- 18 Haxilegen 5850 6080 97.1 5045 98.0 River No. 36.0 Miao’ergou 48 33.0 5400 No. 3 20.3 monsoon 94.0 43.7 5800 38.3 92.0 2005 4850 2005 4600 84.5 75.0 21.8 0.3–9.7 5500 5200 2006 46.0 43.1 5600 43.1 2005 2001 3755 94.3 6350 22.7 Ming 10 et 7 al., 3.3–10.3 2009 2001 2001 Ming 25.3 26.6 et al., summer 2009 2006 7 4510 2001 Xu Xu et 7 et 19.8 al., summer al., 5045 2006 summer 2006 5850 4600 13.3 summer Xu 2005 et al., 5200 2006 10 5800 Xu 5600 et al., 2009 4850 6350 29–75.9 35.5 67.3 8 3755 446 87.4 18.2 22.5 37.2 61.2 129 4510 15.0 Xu et 46.9 al., 2006 Ming Ming et 15.0 26.7 et 15.1 al., al., 2009 2009 89.7 16.7 Ming Xu Xu et et et al., al., 111 al., 2009 2006 2006 Ming Xu et et al., 39.4 al., 2009 2006 Ming et al., 2009 94.5 Ming et al., 2009 Table 2. each glacial site. Units are kg per region per day, averaged over all seasons. Table 1. measurements. Sites we focus on later in the paper are identified with an * in the first column. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | . We that we use

Chem overlaid is - from GEOS

22 21644 21643 nnual mean surface pressure fiveglacier sites in the Himalayas and the Tibetan Plateau AprilJulyOctober 12 200 11 000 29 15 500 000April 11 700 12 900July 3200October 17 5030 400 486 13 7000 000 79 2740 9000 5120 640 151 3920 954 3320 1370 260 74 6 95 0 5 4 48 2260 1760 2870 175 6 3

Location of the of Location National and seasonal origin of BC reaching the atmospheric column above the grid Location of the ﬁve glacier sites in the Himalayas and the Tibetan Plateau that we use Chem. - Mt. Everest January 11 500Mt. Muztagh 6850 January 2490 241 10 300 232 902 162 923 1 552 7 Site Month China India Pakistan Nepal Middle East Africa as receptors in this receptors study.as A Figure 1 compare measured measured concentrations in snow compare BC sites with simulated by of concentrations these at GEOS

as receptors in thiscompare study. measured concentrations Annual of mean BCby surface in GEOS-Chem. pressure snow from at GEOS-Chem these sites is with overlaid. concentrations We simulated Fig. 1. Table 3. box containing Mt. Everestover and each Mt. season. Muztagh sites. Units are kg per region per day, averaged Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

23 23 21646 21645 Seasonal surface means). (January, concentrations BC monthly October July April, and Seasonal surface means). (January, concentrations BC monthly October July April, and Horizontal velocity ﬁelds at the surface and at 550 hPa for January, April, July and Seasonal BC surface concentrations (January, April, July and October monthly means).

Figure 2

October. Each plot representsto an the average period of the usedoverlaid ﬁrst in to color two calculate and weeks include the ofconsidered seasonally origin the here varying are month, of emissions marked corresponding from BC with biomass black reaching burning. squares. the Glacier sites glaciers. Emissions of BC are Fig. 3. Fig. 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

ect (dashed ﬀ we analyze as Glacier sites January, April, July and January, April, and July and snow effect and albedo lines) solid sky estimate corrected for internal mixing. internal for corrected estimate sky -

25 24

21648 21647 ect forcing is a clear-sky estimate corrected for internal mixing. ﬀ adiative forcing due to direct ( r Direct effect forcing is a clear five glacier sites in the Himalayas and the Tibetan Plateau Tibetan the and Himalayas in the sites glacier five

the at Monthly mean : Mt. Everest (Himalayas), Zuoqiupu glacier (southeastern Tibetan Plateau), Meikuang Meikuang Tibetan (southeastern Plateau), (Himalayas), : Mt.Zuoqiupu glacier Everest lines) lines) Horizontal velocity fields at the surface fields 550hPa for at surface the and at Horizontal velocity 3 dashed Continued. Monthly mean radiative forcing due to direct (solid lines) and snow albedo e

Figure 4 ( receptors Plateau), (western (north Mt. Plateau), Tibetan Muztagh and Tibetan (northeastern Miao’ergou of Tibetan Plateau).

Figure of month, the Each to plot first of represents the average October. an two weeks corresponding Emissions overlaid are of the to reaching BC calculate used of BC glaciers. origin the period the seasonally include varying and emissions biomassin burning. color from considered here are marked with black squares.

Fig. 4. lines) at the ﬁvetors: glacier sites Mt. in the(northeastern Everest Himalayas Tibetan and Plateau), (Himalayas), the Mt. Zuoqiupu Muztagh Tibetanof (western glacier Plateau Tibetan Tibetan Plateau). we (southeastern Plateau), and analyze Direct Tibetan Miao’ergou e as (north Plateau), recep- Meikuang Fig. 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper |

Mt. Muztagh (western Tibetan (d) Zuoqiupu glacier (southeastern Ti- (b)

26 27 21650 21649 Mt. Everest (Himalayas), (a) Meikuang (northeastern Tibetan Plateau),

Miao’ergou (north of Tibetan Plateau). The grid box containing each glacier (c) (e) Origin of black carbon by season (January, April, July, October) at ﬁve glacier sites Continued. Fig. 5. betan Plateau), throughout the Third Pole Fig. 5. Plateau), and site is outlined in white.in The the quantity domain of is BC indicated arriving in at color. each glacier grid box from each grid box Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | box

five glacier sites sites glacier at five box from each grid box containing each glacier each boxglacier containing ateau). The grid

28 21651 The quantity of BC arriving at each glacier grid Origin of black carbon by season (January, April, July, October) by season April, October) (January, black July, of Origin carbon

Figure 5 throughout the Third Pole Third Mt. (b) the Everest (Himalayas), (southeastern (a) throughout Zuoqiupu glacier (western Mt. Muztagh Tibetan (d) Tibetan (c) Meikuang Plateau), (northeastern Plateau), Tibetan Pl (e) Miao’ergou Tibetan and of (north Plateau), site is outlined in white. white. in outlined is site in color. in domain is the indicated

Continued. Fig. 5.