TransportModelingIssuesLoriBruhwiler

Con$nentalObserva$onsInfluenceFluxEs$matesLessthanMarineBoundaryObserva$ons

Babenhauserheide,A.,Basu,S.,Houweling,S.,Peters,W.,andButz,A.:ComparingtheCarbonTrackerandTM5-4DVardataassimilaGonsystemsforCO2surfacefluxinversions,Atmos.Chem.Phys.Discuss.,15,8883-8932,doi:10.5194/acpd-15-8883-2015,2015.

CH4intheCanadianArc$c:Con$nentalDataCouldConstrainTerrestrialEmissions

2007 2008 2009 2010 2011 2012 2013

Year

1800

1825

1850

1875

1900

1925

1950

1975Methane(ppb)

StationChurchillBehchokoAlertInuvikCambridge Bay

1800

1825

1850

1875

1900

1925

1950

1975

Alertisa“backgroundsite”,theothersareconGnentalandlikelynearstronglocalsources.

(DatacourtesyofD.Worthy,EnvironmentCanada)

WhatCanBeLearnedFromHigh-FrequencyData?

TownofBarrow

Wetlands

HeterogenousEmissions

“UsingFig.1,fortransportprocessesacorrespondingGmeresoluGon(effT)maybeontheorderofO(U/L)-1.UsinganadvecGvespeedofabout10ms-1wemaygeteffT~(effr/4)/10~30min.Acouplingintervalof60minwouldinthiscasecorrespondtoaneffecGvehorizontalresoluGonof14dx.”GrellandBaklanov,2010

Ls=(z-Hs)TR-1(z-Hs)+(s-sp)TQ-1(s-sp)z=observaGonsHs=simulatedobservaGonssp,s=priorandposteriorsources/sinksQ=priorsource/sinkuncertaintyR=“measurement”uncertainty

TheFluxInversionCostFunc$on

Robs=theactualmeasurementuncertainty(usuallyreallysmall)Rrep=therepresentaGonerrorresulGngfromsub-gridscalevariabilityRtrns=transportmodelerrorsR=(Robs

2+Rrep2+Rtrns

2)1/2

WhatDoestheMeasurementUncertaintyRepresent?

Robs=theactualmeasurementuncertainty(usuallyreallysmall)Rrep=therepresentaGonerrorresulGngfromsub-gridscalevariabilityRtrns=transportmodelerrorsR=(Robs

2+Rrep2+Rtrns

2)1/2

But…1)Errorsareprobablycorrelated.2)Therearealsobiases.3)It’sdifficulttoquanGfytransportR’s

So…1)Understandmodelperformance.

2)Usethebestmodel.

WhatDoestheMeasurementUncertaintyRepresent?

MeridionalTracerGradients

TheTM5gradientistoosteep!(Petersetal.,2004)

TheMeridionalGradienthelpsustoevaluateamodelchange.(hip://www.esrl.noaa.gov/gmd/ccgg/carbontracker/CT2013B_doc)

TheInter-HemisphericGradient

909294969800020406

Patraetal.,2011

Modelsusedthesameemissionssodifferencesareduetotransport

Representa$onError(7kmNASANatureSimula$on)

ModelGridBox

Linetal.,GRL2004;Anempiricalanalysisofthespa$alvariabilityofatmosphericCO2:Implica$onsforinverseanalysesandspace-bornesensors

The variance of differences (variogram) in column-averaged CO2 as a funcGon ofseparaGondistanceh.PointsingreyarevariogramesGmateswithoneobservaGondeleted (Jackknife method). VerGcal bars represent 1-σ errors derived fromJackknife staGsGcs. The solid line represents a power variogrammodel, and thedashedlinescorrespondtothe95%confidenceintervalforthevariogramfit.

Representa$onError

Representa$onError

Linetal.,GRL2004;Anempiricalanalysisofthespa$alvariabilityofatmosphericCO2:Implica$onsforinverseanalysesandspace-bornesensors

DiazIsaacetal.,JournalofGeophysicalResearch:AtmospheresVolume119,Issue17,pages10536-10551,2SEP2014DOI:10.1002/2014JD021593hip://onlinelibrary.wiley.com/doi/10.1002/2014JD021593/full#jgrd51666-fig-0003

TM5(100km)vs.WRF(10km)drivenwithsameCO2fluxes

WRFmayhavebeierverGcalmixingnearsurface.(LEF-WI)

Largedifferencesinmodel-dataresidualsinsummerdrivenenGrelybytransportdifferences.

DiazIsaacetal.,JournalofGeophysicalResearch:AtmospheresVolume119,Issue17,pages10536-10551,2SEP2014DOI:10.1002/2014JD021593hip://onlinelibrary.wiley.com/doi/10.1002/2014JD021593/full#jgrd51666-fig-0003

TM5(100km)vs.WRF(10km)drivenwithsameCO2fluxes

TaylordiagramsummarizesstaGsGcalinfo.onmodel-obsagreement.It’snotobviousthatWRFisbeier!

AssessingTransportErrorusinganEnsembleApproach

Angevineetal.,20146memberWRFEnsembleEnsemblespread(0-100ma.g.l.)suggeststhattransporterrorsforCOmaybesignificant.NormalizedtomeanCO(1meansthatthespreadequalsthemeanarea).

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