1.Background:NISTUrbanTestbedsandtheNECTheNISTurbandomeprogramcurrentlyfundsthreeurban

testbeds,designedtodevelopandtestmethodsforgreenhousegasemissionsestimationinurbanregions:Indianapolis(INFLUX,influx.psu.edu),LosAngeles,(megacities.jpl.nasa.gov),andtheNorth-EastCorridor:Baltimore/Washington(NEC-BW).Allthreetestbedsincludecontinuousin-situmeasurementsofcarbondioxide(CO2)andmethane(CH4)fromtowersandrooftopsintheurbanareas.TheLAandNEC-BWnetworksuseidenticaldataprocessing,dataflaggingandfiltering,calibration,anduncertaintyestimationtechniques,inanefforttostandardizetheseoperations(Verhulst etal,2016;Welp etal.,2013).

TheNEC-BWprojectisacollaborationbetweenNIST,theUniversityofMaryland,ArizonaStateUniversity,EarthNetworks,NOAA,andothers,andincludesairbornecampaignsintheregion(FLAGG-MD,http://aosc.umd.edu/~flaggmd/),meso-scaleandinversemodeling,inventorydevelopment(Hestia),andin-situobservations.Herewepresentsomeinitialresultsfromthein-situNEC-BWnetwork.Currentlythisnetworkconsistsof2existinglong-termEarthNetworkssites(BUCandAWS)and6sitesthathavebeenestablishedsinceOct.2015.Threeofthese(HAL,ARL,andNDC)havebeenoperationalfor>1year.6additionalurbansitesareplannedintheDCarea,alongwith4sitestohelpestablishbackgroundconditions.

(mapsfromGoogle)

GreenhousegasobservationsintheNorth-EastCorridor(Baltimore-WashingtonDC)

NACPAll-InvestigatorsMeetingMarch2017

CARVE

BUC

Code EN Code Location Name Lat Lon Top inlet height (agl)

BUC GHG01 Bucktown, MD 38.46 -76.04 105 m

AWS AWSHQ Germantown, MD 39.20 -77.26 40 m (roof)

HAL GHG48 Halethorpe, MD 39.26 -76.68 58 m

ARL GHG55 Arlington, VA 38.89 -77.13 92 m

NDC GHG56 Northwest, Washington, DC 38.95 -77.08 91 m

NEB GHG58 Northeast Baltimore, MD 39.34 -76.69 55 m

NWB GHG59 Northwest Baltimore, MD 39.32 -76.58 67 m

JES GHG60 Jessup, MD 39.17 -76.78 91 m

JES

AWS

ARL

NDCNEB

NWB

HAL 6.DiurnalCycles&VerticalGradient

BUC

2.NetworkDesignStudy:Urbansites

Sensitivity (monthly average footprint from network)

Figure2:Monthlyaveragesensitivitytofluxes(top)anduncertaintyreduction(bottom)oftheoptimized12towerlocationsinFebruary(left)andJuly(right)2013.

February July

4.CO2 andCH4 Observations

Figure5:MonthlyaverageCO2 (top)andCH4(bottom)atNEC-BWnetworksites(toplevel,allhours).SeeFig.1andTableforsitelocations.

Figure6:Monthlymeanswereaveragedtogetherfor2012-2016(aftersubtractingtheannualglobalgrowthratefromNOAA)toobtainaverageannualcyclesforCO2 (top)andCH4 (bottom)fromBucktown,MD(BUC),andtherooftopofEarthNetworksHeadquartersinGermantown,MD(AWS).

Germantown(AWS)isasuburbofWashington,DCandclosetoamajorhighway.Bucktown(BUC)isontheruralEasternShoreofMaryland,~100kmfromWashingtonDCbutneartheChesapeakeBayandnexttotheBlackwaterNationalWildlifeRefuge,alow-elevationwetlandareawithmanypondsandstreams.HighCH4 atBUCinsummermonths(Fig.6)islikelyindicativeoflocalwetlandemissions.Otherwise,CO2 andCH4 molefractionsareconsistentlyloweratBUCthanothersites.ThemorerecentlyestablishedsitesintheurbannetworkshowmonthlymeansthataresimilartothoseatAWS.

FormoreinformationoraccesstodatafromNEC-BW,pleasecontactAnna.Karion@nist.gov

References• Verhulst,K.etal.,“CarbonDioxideandMethaneMeasurementsfromtheLosAngelesMegacityCarbonProject:1.Calibration,UrbanEnhancements,andUncertaintyEstimates”,Atmos.Chem.AndPhys.Discuss.,doi:10.5194/acp-2016-850,2016.

• LopezCoto etal.,2016,“Tower-BasedGreenhouseGasMeasurementNetworkDesign”,doi 10.1007/s00376-017-6094-6.

ThisworkwassupportedbytheNISTGreenhouseGasMeasurementsProgram.

Figure7:Averagediurnalcycle(averagedover2016)fromeachlevel.

AlltheNEC-BWsites,withtheexceptionoftherooftopatAWS,sampleattwoinletheights(levels).Herewelookatthediurnalcycle(averagedover2016)fromeachlevel.Atmostsites,theverticalgradientisverysmallorclosetozeroduringtheperiodfrom12-16localstandardtime.ThisindicatesthatdespitetheircloseproximitytoCO2 andCH4 sources,thetowersaregenerallyhighenoughtoobservearelativelywell-mixedsignalduringthemid-afternoonhoursoftheday.

Figure1:MapofNortheastCorridor-Baltimore/Washingtontowernetwork.

AnnaKarion1,IsraelLopezCoto1,KimberlyMueller1,Subhomoy Ghosh1,Kuldeep Prasad1,SharonGourdji1,TamaeWong1,JamesWhetstone1,CoryMartin1,2,ChrisSloop3,BillCallahan3,StevePrinzivalli3

1NationalInstituteofStandardsandTechnology,Gaithersburg,MD2UniversityofMaryland,CollegePark,MD3EarthNetworks,Inc.,Germantown,MD

• Networkdesignstudy(OSSE)forlocating12urbantowersites• FossilCO2 emissionsweresampledusingWRF-STILTfootprintsfromcandidatetowersitestocreatesyntheticobservations.

• Clusteringapproachwasusedtoplacethetowersbymaximizingdifferencesbetweensignals(LopezCotoetal.,2016).

AnOSSEwasconductedtoidentifyoptimallocationfortowersthatcharacterizeincomingairflow(i.e.Background),shownasgraytrianglesinFigure1.Analysisshowedtheneedforamoresophisticatedbackgroundanalysisthanhasbeenestablishedinpreviousurbanstudies.Ifthebackgroundtowerdataisusedalone,thevariabilitywillnotbecapturedduetostrongupwindsourcesinthisregion(Muelleretal.,inprep).

3.NetworkDesignStudy:Backgroundsites

Figure4:PredictedCO2signalfromsourcesoutsidetheinnermostdomainasadvectedtothreeoftheurbantowers,showinglargevariabilityofthis“background”signal.

Figure3:Vulcan(Gurneyetal)fossilCO2emissionsshownalongwithNEC-BWfluxestimationdomain(innerredsquare)andouterdomainofinfluence(largerredsquare)consideredinthisstudy.IntheOSSE,CO2 fluxesintheouterdomainweresampledbyWRF-STILTfootprintsfortowersinsidetheinnermostdomaintoreplicatea“background”signal.Sitessurroundingtheinnerdomainwerechosenbasedontheirabilitytosamplethisvariability.

NEC inner domain

DC

O2

(ppm

)

JESARLHAL

(mid-afternoon hours only)

February 2013

Uncertainty reduction from inversion using synthetic observations from 12 ideal candidate sites under a conservative assumption on model errors (5 ppm).