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ScientificreportofSTSM:SoRaXTrenchMeasurementsNameofCandidateandInstitutionDrTomWattsNorthumbriaUniversityUnitedKingdomNameoftheHostInstitutionArcticResearchCentreFinnishMeteorlogicalInstituteSodankylä
PurposeofSTSMThisSTSMwasusedtosupporttravelandsubsistencecostsforTomWatts,anearlycareer researcher (PhDawardedNovember 2015)whowas invited to takepart inSoRaX (SodankyläRadiometer eXperiment) byDr Juha LemmetyinenandMsAnnaKontuoftheFinnishMeteorologicalInstitute,ArcticResearchCentreinSodankylä.SoRaXwasdesignedtoevaluatemicrowaveemissionfromtower-basedradiometersatthefollowingfrequencies:1.4,10.65,21,37,90and150GHz.ThisSTSMwasusedto collect data to quantify spatial heterogeneity in snowpack stratigraphy atcentimetre scale resolution in the vicinity of and underneath the footpint of theradiometers.Spatialchangesinthestratigraphyofthesnowpackinfluencemodelledand observed microwave emission. Quantifying the variability in stratigraphy andrelatedmicrostructurewithinthefootprintoftheradiometerwillenabletheerrorsanduncertaintyinsnowandsnowemissionmodelstobebetterquantified.
DescriptionofworkcarriedoutduringSTSMMeasurements of snowpack stratigraphy were made using near infrared (NIR)photographyinsnowtrenchesdugunderthemicrowaveradiometersattheFinnishMeteorological Institute’sArcticResearchCentre. TheRadiometers arepictured inFigure1.Trenchesweredugataseasonlongsnowpitsiteand30,40,50,60and70degree incidence angles under the radiometer and over a sandbox which wassituatedwithinthescanoftheradiometers.NIR trench methods found in the literature were used to collect data in all thetrenches.Arailwasconstructedinthetrenchandameasuringstaffheldaboveit.Adigital SLR camera adapted to capture light around a centre frequency of 850 nmwas attached to a slider on the rail. A series of photos were taken (as shown in
Figure3)alongtherailtocapturethevariabilityinstratigraphyalongthetrenchatahigh (>1 cm) resolution.Additionally in the snowpit trenchanewstructure frommotion based techniquewas trialed.Measurements of snowmicrostructureweretakenalongthelengthsofallthetrenchesusingIcecube,SnowMicroPenetrometerandsnowgrainmacrophotos.
Figure1:Radiometertowerandundisturbedsnowpack
Figure2:SnowtrenchNIRmethodsbeingusedtorecordhighresolutionsnowstratigraphicinformation
Afterthesnowtrenchmeasurementshadbeenmadeallofthesnowwasclearedfromthefootprintoftheradiometersothatabaregroundmeasurementcouldbemade.
PreliminaryandexpectedresultsAnalysis and post processing is required to digitize the snowpack stratigraphy,howeveranearlyexampleoftheNIRphotographywhichwillbeusedtocreatethehighresolutionsnowpackstratigraphydataisshowinFigure3.
Figure3:ExampleofanNIRphotousedtodigitizesnowpackstratigraphyfromatrenchundertheradiometertower
The trial of the structure frommotion basedmethod used (in addition to the railbasedmethod)atthesnowpitsiteissignificantlyquickertoanalyse,andtheearlyresultsfromthisareshowninFigure4.
Figure4:Trenchimageproducedfromstructurefrommotiontechniques
Over the coming months Tom Watts will digitize all of the snow trenches andgeolocate them inside the field of view of the microwave radiometers. This willenableevaluationofsnowmicrowaveemissionmodelsundertheradiometer.
ExpectedPublicationsandoutcomesfromSTSMAcombineddatasetofradiometer,andsnowdatawillbeusedtoproduceatleastonepublicationincollaborationwithFMIaddressingtheaccuracyofthen-HUTsnowmicrowave emission model snow when high-resolution snowpack stratigraphy isusedinthreedifferentways:
o To run an ensemble of simulations from within the radiometerfootprint
o To create an average value for each layer in the stratigraphy acrossthefootprint
o Tocreateanoverall averagebulk single layer value forall the snowwithinthefootprint.
Other publications are anticipated which will relate measurements from specificradiometerstothesnowstratigraphythroughouttheseason.ThesewillalsousethesnowtrenchdatacollectedaspartofthisSTSM.Collaborationwiththehost institutionwillberequired inorderforthispublication(andotheranticipatedpublications)tobeproduced,initialpoolingofdataisalreadyunderwaywith themajority of the analysis expected to be carried outwithin thecomingmonths.
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