AERONETVersion3DatabaseUpdateandEvalua:on

ThomasEck1,2,DavidGiles1,3,BrentHolben2,IlyaSlutsker1,3,JoelSchafer1,3,AliaksandrSinyuk1,3,AlexanderSmirnov1,3,MikhailSorokin1,3

1Universi:esSpaceResearchAssocia:on2NASAGoddardSpaceFlightCenter

3ScienceSystemsandApplica:ons,Inc.AeroCom/AeroSat

Helsinki,FinlandOct12,2017

AERONET Aerosol Robotic Network- Over Twenty-Four Years of Observations and Research

AERONET provides a long-term, continuous public database of aerosol optical,

microphysical, and radiative properties for aerosol research and characterization, validation of satellite

measurements, and synergism with other databases.

The AERONET program is a federation of ground-based remote sensing aerosol networks established by NASA and LOA-PHOTONS (CNRS) and has been expanded by collaborators from international agencies, institutes, universities, individual scientists and partners. 15May

1993

•  >7000cita:ons•  >450sites•  Over90countriesandterritories•  hWp://aeronet.gsfc.nasa.gov

15May2017

AERONETVersion3:AOD•  V3Level1.0:Unscreeneddata(NRT)

–  Appliesnewtemperaturecharacteriza9ons–  AppliesNO2&O3OMIL3climatology(2004-2013)–  Appliesupdatedabsorp:oncoefficients

(Literature/HITRAN)•  V3Level1.5:BasedonLevel1.0andusesnew

automa9cqualitycontrols(NRT)–  CloudScreening

•  Improvesremovalofop9callythincirruscontamina9on•  PreservesmorehighlyvariablefinemodeAOD•  CompareswelltoVersion2Level2

–  QualityControls•  Removessensortemperaturear9facts•  RemovesAODimpactedbywindowobstruc9ons•  RemovesAODwithpoorspectraldependence•  RemovesAODaffectedbysolareclipses

•  V3Level2.0:BasedonLevel1.5withpre-andpost-calibra:onapplied

–  Significantlyimproves:melinessofLevel2.0dataavailability

–  Appliesanobjec:veremovalscheme–  Nomanualanalysis

V2TemperatureCorrec:on

V3TemperatureCorrec:on

V2vs.V3CloudScreeningAlgorithm/Parameter Version2 Version3

VeryHighAODRestora9on N/A τ870>0.5;α675-1020>1.2orα870-1020>1.3,restoreifeliminatedbycloudscreening

AirMassRange 1to5 1to7

NumberofPoten9alMeasurements

N<3,rejectday

Aherallchecksapplied,rejectdayifNremain<MAX{3or<10%ofN}

TripletCriterion Allλs;AODrange>MAX{0.02or0.03*τa}

λ=675,870,1020nmAODrange>MAX{0.01or0.015*τa}

AngstromLimita9on N/A IfAElessthan-1.0orAEgreaterthan4.0,theneliminatemeasurement.

SmoothnessCheck D<16 ForAOD500nm(or440nm)Δτa>0.01perminute,removelargerτainpair.Then,theprocessrepeatsun:lnomoreremoval.

•  V2:Smirnovetal.2000,CloudscreeningandqualitycontrolalgorithmsfortheAERONETdatabase,Rem.Sens.Env.,73,337-349

•  AERONETVersion3AODAlgorithmQualityControlTechnicalDescrip:on(2017)

V2vs.V3CloudScreeningAlgorithm/Parameter Version2 Version3

SolarAureoleRadianceCurvatureCheck

N/A Computecurvature(ƙ)for1020nmaureoleradiancesfrom3.2°-6.0°φ.Ifƙ<2.0E-5,computeaslopeoflnƙvslnφ.Ifslopeisgreaterthan4.3(empiricallyderived),thenpointis“cloudcontaminated.”ForALM,PP,andHYB,allτapointswillberemovedinthe±30minutesperiodfromskymeasurement.

StandalonePoints N/A Nodata±1hourofpoint,thenrejectitunlessα440-870nm>1.0,thenkeeppoint

AODStabilityCheck SameasV3 DailyAveragedAOD500nm(or440nm)hasσlessthan0.015,thendonotperform3-SigmaCheck

3-SigmaCheck SameasV3 AOD500nmandα440-870nmshouldbewithinMEAN±3σ;otherwiserejectpoint(s)

CloudScreeningAlgorithmStepChangeSummary:2same,4modified,and4new

Level1.5QualityControls•  RawDataChecks–sensortemperature,digitalcounts,clockshih,etc.•  Collimatorconsistencychecks•  AODdiurnaldependencechecks•  AODspectraldependencechecks•  Solareclipsescreening

•  AERONETVersion3AODAlgorithmQualityControlTechnicalDescrip:on(2017)

Level2.0AODCriteria•  MustpasstheLevel1.5criteria•  Mustu:lizepre-fieldandpost-fieldcalibra:on•  Temperaturecharacteriza:onmustbeappliedforallvisibleandnear-

infraredchannels(440-1640nm);Nocharacteriza:onforwavelengths<440nm

•  Oncecalibra:onassessmentiscomplete,a30-daypausewillbemadetoallowthelatestupdatesfromancillarydata

IndonesianFires2015(Palangkaraya)–CurrentV2

RemovedbyV2cloudscreeningCirruscontamina:on

Cloudcleareddata(V2Level1.5)

PalangkarayaAquaMODIS20151005T06:05UTC

Version3L1.0Data

DetectableSignal

Op:callythincirruscloudsremovedBiomassburningsmokerestoredforhighaerosolloadingevents

Version3BetaL2.0QAData

MainlyNIRandSWIRλRange

Palangkaraya, Indonesia Aug 01- Nov 15, 2015

Many Very Heavy smoke AOD days were missed in AERONET V2 due to insufficient direct sun signal in the UV and visible wavelengths

AERONET Cimel 4 quadrant detector is sensitive in the Near Infrared allowing sun tracking when solar disc not detectable in the shorter wavelengths (large Angstrom Exp. for

Smoke)

NewV3AlgorithmRetainsAODdataforlongestwavelengthswhensolardirectbeamsignalstrengthissufficientandAngstromExponent(870-1020nm)>1.3

AOD at 675 nm shows maximum value at ~7 This is approximately the limit of sunphotometry with high sun

(optical airmass near to 1); otherwise for AOD*airmass<7

Thesees9matedAODlevelsatmid-visibleexceed(toourknowledge)anyvalueseverreportedinthepublishedliterature.Thisbiomass-burningeventin2015inIndonesiawasthelargestmagnitudeAODeventintermsofAODlevelsevermonitoredbyAERONETtodate,inthe24-yearhistoryofthenetwork

Ecketal.,inprepara:on

AERONETV2vs.V3

Singapore,#22,2007-2011Level N AOD αV2L1.0 25500 0.61 0.86V2L1.5 8680 0.46 1.03V2L2.0 6920 0.35 1.20V3L1.5CldScr 6876 0.35 1.52V3L1.5 6597 0.35 1.51V3L2.0Beta 6597 0.35 1.51

Nauru,#168,2000-2005,2010Level N AOD αV2L1.0 25579 0.23 0.31V2L1.5 13326 0.11 0.47V2L2.0 9371 0.08 0.54V3L1.5CldScr 10233 0.07 0.47V3L1.5 8917 0.06 0.52V3L2.0Beta 8917 0.06 0.52

•  NewLevel1.5AOD500nmandα440-870nmsta:s:callyveryclosetoV2Level2.0averagesformanysites

•  ImproperlyfilteredhighlyvariableAODs(dominatedbyfineaerosols)mayberestoredintheV3database

•  Stablethincirrusbecomeslessofanissue(lessresidualcontamina:on)

•  V3L1.5andV3L2.0Betainmanycasesareexpectedtobeverysimilar

ClimatologyAE

AOD

AE AOD

AE

AOD

AE

AOD

Seoul, S. Korea – Major 5 day pollution event from May 27-31, 2012 Version 2 Level 2 Cloud Screening eliminated 3 days – May 28-30

These 3 days are retained in Version 3 level 2 data.

Fine Mode High AOD Days – Many more days eliminated by Version 2 screening than Version 3 screening in China and Korea

AERONETVersion3Update-Inversions

•  MERRA-2aerosolex:nc:onprofiles

•  MODISBRDF(snowandsnow-free)

•  UpdatedASTMStandardExtraterrestrialSpectrumE-490-00a(reapproved2006)

•  FullVectorradia:vetransfercode–  SuccessiveORDersofscaWering(SORD)–  radia:onfieldinUV(e.g.,380nmretrievalinfuture)

–  degreeoflineardepolariza:on

MODISNBARJanuary1-8,2013

AERONETVersion3Update-Inversions•  MaintainV2inversionproduct

QualityChecks(Holben2006)

•  NASASupercomputers(GSFCandAmes)processingwithhelpfromArlindoDaSilva

•  Es:mateduncertain:es(e.g.,biasesduetouncertaintyinAODandskyradiancecalibra:onplussurfacealbedo)

Kanpur,India

Version 3 - Significant increases in slope of SSA versus wavelength in V3 (440 nm increases while 870 and 1020 nm decrease)

Version 3 - Significant increases in slope of SSA versus wavelength in V3 (440 nm increases while 870 and 1020 nm decrease)

Wave (nm) V2 Ext. Irrad V3 Ext/ Irrad. Ratio V3/V2 1020  692.67 707.06 1.021 870  933.10 953.68 1.022 675  1530.23 1511.29 0.988 440 1853.88 1822.62 0.983 .

0

0.05

0.1

0.15

0 0.5 1 1.5 2

GSFCMonguAgoufouKanpurAverage

Ince

rtai

nry

in S

SA(4

40)

AOD, 440 nm

SZA=60

0

0.05

0.1

0.15

0.2

0 0.5 1 1.5 2

SZA=60

GSFCMonguAgoufouKanpurAverage

Unc

erta

inty

in S

SA(6

70)

AOD, 440 nmAngstrom Exponent (440-870 nm)

GSFC – 1.75 Mongu – 1.84 Agoufou – 0.12 Kanpur - 0.70

440 nm 675 nm

UncertaintyinAerosolSingleScaderingAlbedo–Version3

Computedassuminguncertain:esin:AOD(0.01atm=1),SkyRadiance(3%calibra:on),SurfaceAlbedo(MODISproduct=0.05),Poin:ngerror(0.1degree)

UncertaintyinAerosolSingleScaderingAlbedo–Version3

0

0.05

0.1

0.15

0.2

0.25

0 0.5 1 1.5 2

SZA=60

GSFCMonguAgoufouKanpurAverage

Unc

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inty

in S

SA(8

70)

AOD, 440 nm

0

0.05

0.1

0.15

0.2

0.25

0 0.5 1 1.5 2

SZA=60

GSFCMonguAgoufouKanpurAverage

Unc

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inty

in S

SA(1

020)

AOD, 440 nm

Angstrom Exponent (440-870 nm) GSFC – 1.75 Mongu – 1.84 Agoufou – 0.12 Kanpur - 0.70

870 nm 1020 nm

AERONETNewInstrumenta:on/Enhancements

•  Improvedtrackingreducingtripletvariance

•  Greatercontroloverinstrumentmeasurementscenarios(e.g.,Hybrid)

•  Addi:onalcapabili:essuchasSDcardstorage,GPS,USB,andZigbee

•  Lunarmeasurements–  1stto3rdquarterlunarphase(waxingto

waninggibbous)–  Processingforlunarmeasurements(e.g.,ROLO,

TomStone)

•  DevelopmenttowardaWachmentforCO2measurements(EmilyWilson)

•  SynergismwithMPLNET,PANDORA,andinsitumeasurements CimelSun/Sky/LunarRadiometer

HybridScanresultsinmanymoreretrievalsatAOD>2at440nmsinceHybridscanscanbemadeatmid-daywithlowSolarZenithAngle(SZA).AlmucantarscansrequireSZA>50degrees–thisresultsininsufficientsignaltomeasure440nmAODwhenAODisveryhigh

SummaryandOutlook•  HigherqualityAODdatawillbeavailableinV3

– Duetotemperaturecharacteriza:onandautoma:ccloudscreeningandqualitycontrols

•  Level2.0u:lizesLevel1.5automa:cscreeningandavailablewithin30daysofpost-fieldcalibra:onapplica:on

•  V3inversionswillu:lizenewradia:vetransfer,ancillarydatasets,andprovidenewproducts

Ø V3AODLevel1.0andLevel1.5NRTreleasedØ V3AOD&InversionsLevel2.0expectedrelease:October-November2017

ForwardModellingwithRTcodeSORD•  NewpubliclyavailablepolarizedRTcode:SORD

(SuccessiveORDersofscaWering)•  TheSORDcodeislocaltotheAERONET:easytosupportand

furtherdevelop•  BothspeedandaccuracyarepublishedinJQRSTmanuscriptusing

52benchmarks•  ManuscriptexplainshowtogetSORDandindependently

reproduceallthetests

AERONETV3L1.5:AODSpectralDependence

•  U:lizemainly1stor2ndorderfit•  Numberofwavelengths•  AODmagnitude

•  Usesrobustregressiontechniquelessinfluencedbyoutliers

•  Employitera:veapproachtoremoveoutliersbasedonfit(fit-measurement)

•  Combinewithotherscreening

techniques

0.5-

0.4-

0.3-

0.2-

0.1-

0.0-

-0.1-AnomalouslylowAOD380nm

Level1.5CloudScreenedOnly