AS5537_final.docx

SAsAerospaceaerospaceAnSAEInternationalGroupSTANDARDSAEAS5537REV.AIssued2004-05ReViSSdPrOoOSedDraft2013-04-05SuoersedinaAS5537WeatherSupporttoDeicingDecisionMaking(WSDDM)WinterWeatherNowcastingSystemRATIONALETheoriginalmotivationfortheWSDDMSystemwasoriginallydevelopedtoprovideflightlinedeicingoperatorsthemostup-to-dateandrelevantweatherinformationonwhichtobasetheirdeicingdecisions.Thesystemhasalsobeenhighlyusefultoairportauthoritiesforsnowcrewmanagementofrunway,taxiway,androad-plowingactivities,aswellasandaircarriersforgroundde/anti-icingoperations,departurescheduling,andregionalairtrafficfacilitiesforwinterweatherairtrafficoperations.Akeyelementofthesystemistheuseofoneormoreprecisionsnowgauges,whichprovidereal-timeestimatesoftheliquidequivalentsnowfallrateeveryminute.Thismeasurementisessentialtodeicingoperationsduetothedeterminationbythedeicingcommunitythattheliquidequivalentsnowfallrateisthekeyfactorleadingtothefailureofdeicing/anti-icingfluids.CurrentNationalWeatherSurfaceMETARstationsdonotprovideliquidequivalentsnowfallrates,butratherhourlysnowintensityestimatesbasedonvisibility.Snowintensityestimatesbasedonvisibilityhavebeenshowntobemisleadingwhenwetsnow,heavilyrimedsnow(snowthathasaccretedsignificantamountsofliquidclouddroplets),andsnowcontainingsinglecrystalsofcompactshape(nearlyspherical)occur.Researchershavedefinedthishazardashigh-VisibiIityZhigh-SnowfaIIrateconditions.Examinationoffiveofthemajoraircraftgrounddeicingaccidentshasshownthathighvisibility-highsnowfallrateconditionswerepresentduringanumberoftheseaccidents.Alloftheaccidentshadnearlythesameliquidequivalentrateof2.5mm/hour(0.1inch/hour),butwidelyvaryingvisibilities.TheWSDDMSystemwasdesignedtodirectlyaddressthisconcernbyincludingsnowgaugesthatmeasureliquidequivalentsnowfallrateeveryminuteasoneofitscorecomponents.AnotherimportantcomponentoftheWSDDMSystemisthe1-hournowcastofsnowfallratebasedonacombinationofradarreflectivityandprecipitationgaugedata.Thesenowcastsaredeterminedbyapplyingacalibrationfactortothereflectivitybasedonactualratesfromthegaugesandthentrackingthemovementofthereflectivity.AdditionalfeaturesoftheWSDDMSystemincludes:(1)real-timeradarreflectivityfromWSR-88Dradarsdepictingcurrentlocationsofprecipitation,(2)meteorologicaldataattheairportandtwoormoresitesupto80km(-50miles)awayfromtheairportupdatedeveryminuteanddisplayedintextandgraphical(timeline)form,withthetimelinegoingbackaminimumof2hours,(3)aone-hournowcastofradarreflectivitybasedontheuseofacrosscorrelationtechniqueoftheradarreflectivitydataupdatedeverysixtotenminutes,and(4)adepictionofthecurrentweatherconditionsfromNationalWeatherServiceMETARhourlyreportsorspecialreportsintextformatandalsodepictedgraphicallywithintheWSDDMradardisplay.FOREWORDThisSAEAerospaceStandard(AS)recommendssettingguidelinesforthedeploymentoftheWeatherSupporttoDeicingDecisionMaking(WSDDM)winterweathernowcastingsystematsite-specificairports.Theyareintendedtoprovide(1)therelevantinformationtolocate,operate,andmaintainsuchsystemsand(2)hardwarespecificationsfortheequipmentrequiredtobuildandoperatesuchsystems.SAETechnicalStandardsBoardRulesprovidethat:ThisreportispublishedbySAEtoadvancethestateoftechnicalandengineeringsciences.Theuseofthisreportisentirelyvoluntary,anditsapplicabilityandsuitabilityforanyparticularuse,includinganypatentinfringementarisingtherefrom,isthesoleresponsibilityoftheuser."SAEreviewseachtechnicalreportatleasteveryfiveyearsatwhichtimeitmayberevised,reaffirmed,stabilized,orcancelled.SAEinvitesyourwrittencommentsandsuggestions.Copyright©2013SAEInternationalSAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.ora/technical/standards/PRODCODEAllrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystemortransmitted,inanyformorbyanymeans,electronic,mechanical,photocopying,recording,orotherwise,withoutthepriorwrittenpermissionofSAE.TOPLACEADOCUMENTORDER:Tel:877-606-7323(insideUSAandCanada)Tel:+1724-776-4970(outsideUSA)Fax:724-776-0790Email:CustomerServicesae.orgSAEWEBADDRESS:httpJ/www.sae.orgIngeneral,theWSDDMSystemisanautomatedsystemthatproducesreal-timeanalysesandshort-termnowcastsofwinterweatherconditionsintheairportterminalarea.Thedatausedbythesystemareprovidedfromprecipitationgauges,weatherradars,surfaceweatherstations,andNationalWeatherServiceAviationRoutineWeatherReport(METAR)datageneratedfromAutomatedSurfaceObservingSystems(ASOS).ThesedataareprocessedbytheWSDDMsoftwaretoproducegraphicalandtextualdepictionsofthecurrentweatherconditions.Aone-hourforecastofexpectedprecipitationratesattheairportisalsoproducedandupdatedeverysixtotenminutes,dependingonthefrequencyofnewdatareceivedfromtheweatherradars.Theresultinganalysesandforecastsaredisplayedviaawebpageorondedicatedcomputersystemsinauser-friendlyformatthatiseasilyunderstoodbynon-meteorologists.DetailsregardingthegraphicaldisplayandthecomputeralgorithmsusedtogeneratethedisplayaregivenintheWSDDMarticleintheBulletinoft