MULTI-SCALEL-BANDBRIGHTNESSTEMPERATUREANALYSISFORSOILFREEZINGANDTHAWINGPROCESS

STUDY

AlexandreRoy,U.Sherbrooke-EnvironmentCanadaAlainRoyerandAlexandreLanglois,U.Sherbrooke,Québec,Canada

ChrisDerksenandPeterToose,EnvironmentCanadaLudovicBrucker,GSFC-NASA

ArnaudMialonandYannKerr,CESBIO-CNES

MicroRad2016,Helsinki,Finland

https://ntrs.nasa.gov/search.jsp?R=20160005217 2020-05-17T01:02:54+00:00Z

*  Surfaceenergybalance*  Netcarbonfluxesinborealandsub-arcticregions*  Permafrostmonitoring*  Hydrologicalapplications

SurfaceFreeze/ThawRational:

Overone-thirdofthegloballandareaundergoesaseasonaltransi4onbetweenpredominantlyfrozenandnon-frozencondi4onseachyear.Closelylinkedto:•  4mingandlengthofthevegeta4ongrowingseason•  seasonalevolu4onofland-atmospherecarbon

dioxideexchange•  interac4onsbetweensoilprocessesandsnowmelt

ThelandsurfaceF/Tstateactsasanaturalon/offswitchforhydrologicalandbiosphericprocessesovernorthernlandareasandathigheleva4ons. Averagenon-frozenperiod(top)and(boGom)standard

devia4onofthenon-frozenperiod[daysyr−1]derivedfromSSM/Idata(1988–2007)

SMOSF/Tproduct

Rau%ainenetal.,RSE,2014

•  FTes4matesderivedfromSMOS1.4GHzL-bandradiometermeasurements

•  45kmspa4alresolu4on•  Lesssensi4vetosnow&vegeta4on;RFIposesachallenge

ExampleFTclassifica4onderivedfromSMOSmeasurements

REF

L-BandSpaceborneRadiometers

Mission LRD Measurement Instrument

Complement

Radiometer Resolution/

Revisit

Incident Angle (°)

SMOS (1)

Nov. 2009 -…

Soil Moisture Ocean Salinity

L-band radiometer

50 km / 3 days 0-65

Aquarius (2)

Aug. 2011 – Jun. 2015

Ocean Salinity Soil Moisture

L-band radiometer, Scatterometer

100 km / 7 days Beam 1: 29.2 Beam 2: 38.4 Beam 3: 46.3

SMAP (3)

Apr. 2015 - …

Soil Moisture Freeze/Thaw state

L-band radiometer

40 km / 2-3 days

40

(1)SMOSWeeklyaveragedfromdailyreconstructedTB(L3TB)(www.catds.fr/sipad/)(2)Aquariusweekly-polargriddedTBversion3.0(Bruckeretal.,TheCryosphere,2014)(3)SMAPNSIDC:LC1,TBEaseGrid36km

*  EvaluateNormalizedPolarizationRatio(NPR)-basedF/Tdetectionalgorithm*  SMOS*  Aquarius

*  Evaluatetheinfluenceoflandcoverandsensorconfiguration(angle)onF/Tdetection

RoyA.,A.Royer,C.Derksen,L.Brucker,A.Langlois,A.Mialon,Y.H.Kerr(2015)EvaluationofSpaceborneL-bandradiometermeasurementsforterrestrialFreeze/ThawretrievalsinCanada,IEEEJSTARS,DOI:10.1109/JSTARS.2015.2476358.

Objective#1SMOSandAquariusF/T

HV

HV

TBTBTBTBNPR

+

−= FFrel =

NPR(t)− NPRfr

NPRth − NPRfr

FFrel<Δ→freezeandifFF(t)>Δ→thaw

RelativeFrostFactor(FFrel)

StudySites

Soilandairtemperaturesandsnowmeasurements7tundra,8borealforestand35prairiesites

*  Surface temperature : weekly binary (F/T) datasets *  Insitusoiltemperature(2to5cm)*  Insituairtemperature*  CloudfreeMODISlandsurfacetemperature(MODISLST)

if majority of X -< 0 = frozen week

*  Cloud free MODIS snow cover area (MODISSCA) if majority of SCA>10% = frozen week

AncillaryData

Accuracy = # correct predictions / total weeks(%)

Objective1:ResultsThreshold(∆)evaluationwithAquarius

•  Best Accuracies with Tair •  Best accuracies over Tundra and worst over Prairies •  Tundra : broad range in the treshold (0.3 to 0.7) •  Optimized treshold at 38.4°: forest = 0.46; Prairies = 0.39 •  For SMOS: best Accuracies with higher incidence angle (60°) → larger V-H at Brewster

Forest Prairies

Accu

racy

Objective1:ResultsTundratemporalseries(Salluit)SMOS&Aquarius

•  ClearNPRF/Tsignalintundra•  SMOSat55-60°andAquariusat38.9°

Aquarius

SMOS

2011 2013

•  Latitude=69.13N•  GoodF/Tsignal•  Influenceoflakes(TBdropinJuly)

SMAPNSIDC:LC1,TBEaseGrid36km

Objective1:ResultsTundratemporalseries(CambridgeBay)SMAPF/T

Objective1:ResultsBorealForesttemporalseries(Kuujjuarapik)

•  SmootherF/Ttransition(vegetationsoilcontinuum)•  SMOSat55-60°andAquariusat38.9°

Aquarius

SMOS

Objective1:ResultsBorealForesttemporalseries(Baie-James)SMAPF/T

•  Soilbarelyfrozen(evenwithTair<-40°C)•  MorethawwithAscpasses/morefreezewithDscpasses•  Clearsignalwiththepresenceofsnow•  Differencesbetweenfore-andaft-look SMAPNSIDC:LC1,TBEaseGrid36km

Objective1:ResultsPrairiestemporalseries(Alberta)

•  F/Tsignalislessclear•  TBincreaseduringsummers→seasonalcropgrowthcycle•  Manymelteventsinwinter•  SMOSat55-60°andAquariusat38.9°

Aquarius

SMOS

Objective2:SpatialvariabilityFreezeonsetandFreezeendsmaps(SMOS)

Freezeonsetinweeks(Fall) Freezeendinweeks(Spring)

2011 2011

2012 2012

Objective2:SpatialvariabilitySnowmelteffect(GreatBearLake)

•  Purelakepixel(GreatBearLake)•  HighNPRandlowTBinsummer(water)•  LowNPRandhigherTBinwinter(ice)•  HigherTBduringspringsnowmelt(wetsnow)

Aquarius

SMOS

Objective2:SpatialvariabilitySurface-basedvsSMOSTB(Prairies)

Meansurface-basedradiometerTBandstandarddeviationfor7sitesovertheKenastonregion,PrairieswithinthesameSMOSpixel(2baresoil,1grass,1pasture,3cropstubble)

V

HSMOSangularlysmoothedTBSurface-based

radiometerUnfrozensoil

Frozen

ProblemofthehighbeamwidthoftheSBR(30ºhalf-power)

*  L-bandNPRissensitivetoF/T*  ButdonotusethefullpotentialofSMOS(weeklyvs3daysTBandversion243)*  ApplicationsforSMOPinprogress…*  BettercorrelationwithTair(withthelimitationofpointmeasurements)

-  Snowmeltsignalinspring-  Soiltemperature(2to5cm)=delay-  Sensitivetosurfacefreezing

*  Vegetation-soilcontinuumsignalinborealforest*  Needabetterunderstanding/decouplingofFTsignalinborealforest

(vegetationphenologyvssoilFT)

*  InterestingspatialpatternofF/Tvariability(Rain-On-Snowevents)*  GoodagreementbetweenSBRandSMOSTB,exceptedat60°

ConclusionOverallaccuracyforF/Tdetection:

90,8%Aquarius87,8%SMOS

*  Centred’ÉtudesNordiques(CEN)

*  AlanBarrandUniversityofSaskatchewan(BERMS)

*  UniversityofGuelf

*  SharonSmith(NaturalResourcesCanada)

*  PhilMarsh(TrailValley)

*  PeterLafleur(DaringLake)

*  AgricultureandAgri-FoodCanada(AAFC)

*  AgricultureAlberta(ACIS)

ThankstoInsitudataproviders

AndSpatialAgencies:ESA,CNES,NASA,CSA

Thanksforyourattention