Global budget of methanol Constraints from atmospheric obser

[1] We use a global three-dimensional model simulation of atmospheric methanol to examine the consistency between observed atmospheric concentrations and current understanding of sources and sinks. Global sources in the model include 128 Tg yr 1 from plant

JOURNALOFGEOPHYSICALRESEARCH,VOL.110,D08303,doi:10.1029/2004JD005172,2005

Globalbudgetofmethanol:Constraintsfromatmosphericobservations

DanielJ.Jacob,1BrendanD.Field,1QinbinLi,1,2DonaldR.Blake,3JoostdeGouw,4CarstenWarneke,4ArminHansel,5ArminWisthaler,5HanwantB.Singh,6andA.Guenther7

Received28June2004;revised5January2005;accepted2February2005;published26April2005.

[1]Weuseaglobalthree-dimensionalmodelsimulationofatmosphericmethanolto

examinetheconsistencybetweenobservedatmosphericconcentrationsandcurrent

understandingofsourcesandsinks.Globalsourcesinthemodelinclude128TgyrÀ1fromplantgrowth,38TgyrÀ1fromatmosphericreactionsofCH3O2withitselfandotherorganicperoxyradicals,23TgyrÀ1fromplantdecay,13TgyrÀ1frombiomassburningandbiofuels,and4TgyrÀ1fromvehiclesandindustry.Theplantgrowthsourceisafactorof3higherforyoungthanfrommatureleaves.Theatmosphericlifetimeofmethanolinthemodelis7days;gas-phaseoxidationbyOHaccountsfor63%oftheglobalsink,drydepositiontoland26%,wetdeposition6%,uptakebytheocean5%,andaqueous-phaseoxidationincloudslessthan1%.TheresultingsimulationofatmosphericconcentrationsisgenerallyunbiasedintheNorthernHemisphereandreproducestheobservedcorrelationsofmethanolwithacetone,HCN,andCOinAsianoutflow.

Accountingfordecreasingemissionfromleavesastheyageisnecessarytoreproducetheobservedseasonalvariationofmethanolconcentrationsatnorthernmidlatitudes.ThemainmodeldiscrepancyisovertheSouthPacific,wheresimulatedconcentrationsareafactorof2toolow.AtmosphericproductionfromtheCH3O2self-reactionisthe

dominantmodelsourceinthisregion.Afactorof2increaseinthissource(to50–100TgyrÀ1)wouldlargelycorrectthediscrepancyandappearsconsistentwithindependentconstraintsonCH3O2concentrations.Ourresultingbestestimateoftheglobalsourceofmethanolis240TgyrÀ1.Moreobservationsofmethanolconcentrationsandfluxesareneededovertropicalcontinents.BetterknowledgeisneededofCH3O2concentrationsintheremotetroposphereandoftheunderlyingorganicchemistry.

Citation:Jacob,D.J.,B.D.Field,Q.Li,D.R.Blake,J.deGouw,C.Warneke,A.Hansel,A.Wisthaler,H.B.Singh,andA.Guenther(2005),Globalbudgetofmethanol:Constraintsfromatmosphericobservations,J.Geophys.Res.,110,D08303,doi:10.1029/2004JD005172.

1.Introduction

[2]Methanolisthesecondmostabundantorganicgasintheatmosphereaftermethane.Itispresentattypicalcon-centrationsof1–10ppbvinthecontinentalboundarylayerand0.1–1ppbvintheremotetroposphere[Singhetal.,1995;Heikesetal.,2002].Itisasignificantatmosphericsourceofformaldehyde[Riemeretal.,1998;Palmeretal.,2003a]andCO(B.N.Duncanetal.,Globalmodelstudyof

DivisionofEngineeringandAppliedScience,HarvardUniversity,Cambridge,Massachusetts,USA.

2

NowatJetPropulsionLaboratory,Pasadena,California,USA.3

DepartmentofChemistry,UniversityofCalifornia,Irvine,California,USA.

4

NOAAAeronomyLaboratory,Boulder,Colorado,USA.5

InstituteofIonPhysics,UniversityofInnsbruck,Innsbruck,Austria.6

NASAAmesResearchCenter,MoffettField,California,USA.7

AtmosphericChemistryDivision,NationalCenterforAtmosphericResearch,Boulder,Colorado,USA.

Copyright2005bytheAmericanGeophysicalUnion.0148-0227/05/2004JD005172$09.00

1theinterannualvariabilityandtrendsofcarbonmonoxide(1988–1997):1.Modelformulation,evaluation,andsensi-tivity,submittedtoJournalofGeophysicalResearch,2004,hereinafterreferredtoasDuncanetal.,submittedmanu-script,2004),aswellasaminorterminthecarboncycle[Heikesetal.,2002]andintheglobalbudgetsoftropo-sphericozoneandOH[Tieetal.,2003].Mostoftheobservationsofatmosphericmethanolconcentrationscon-sistofshort-termrecordsinsurfaceair[Heikesetal.,2002].Recentaircraftmissionshaveaddedanewdimensiontoourknowledgeofmethanolconcentrationsintheglobaltropo-sphere[Singhetal.,2000,2001,2003a,2004;Lelieveldetal.,2002].Weusehereaglobal3-Dchemicaltransportmodel(CTM)toexaminetheconstraintsthattheseaircraftobservationsprovideoncurrentunderstandingofmethanolsourcesandsinks.

[3]GlobalbudgetsofatmosphericmethanolhavebeenpresentedpreviouslybySinghetal.[2000],GalballyandKristine[2002],Heikesetal.[2002],Tieetal.[2003],andvonKuhlmannetal.[2003a,2003b].TheyaresummarizedinTable1.Plantgrowthistheprincipalsource.Additional

[1] We use a global three-dimensional model simulation of atmospheric methanol to examine the consistency between observed atmospheric concentrations and current understanding of sources and sinks. Global sources in the model include 128 Tg yr 1 from plant

Table1.GlobalAtmosphericBudgetsofMethanolReportedintheLiterature

Reference

PlantgrowthPlantdecay

BiomassburningdUrbane

AtmosphericproductionfTotalsource

Gas-phaseoxidationbyOHIn-cloudoxidationbyOH(aq)Drydeposition(land)OceanuptakekWetdepositionTotalsinks

Atmosphericinventory(Tg)Atmosphericlifetime(days)

ab

Singhetal.[2000]a75(50–125)20(10–40)6(3–17)3(2–4)18(12–24)122(75–210)

Heikesetal.[2002]aGalballyandKirstine[2002]aTieetal.[2003]b104–312

vonKuhlmannetal.[2003a,2003b]

771522812377i379123

ThisWorkc128(100–160)23(5–40)13(10–20)4(1–10)38g(50–100)206h(170–330)129j<15510122064.0

7(5–10)

Sources(TgyrÀ1)

280(50–>280)100(37–212)20(10–40)13(5–31)12(2–32)13(6–19)8(5–11)4(3–5)30(18–30)19(14–24)350(90–490)149(83–260)Sinks(TgyrÀ1)100(25–150)109(60–203)10(5–20)5(2–15)70(35–210)24(11–43)50(À20–150)0.3(0.2–0.6)10(4–36)11(5–20)270(160–570)149(82–273)3.93.4

89(5)m

31

135–34359–14932–8516–50107–2841.9–4.712

40–50

l

Bestestimatesandrangesinparentheses.

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