A physically-based method for classification of precipitation types …€¦ · classification of...
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A physically-based method for classification of precipitation types and the implications for future changes over Norway Stefan Sobolowski 1 ; Basile Poujol 1,2 ; Ségolène Berthou 3 ; Steven Chan 3 ; Torge Lorenz 1 ; Priscilla Mooney 1 22 AUGUST, 2019 LATSIS SYMPOSIUM, ETH ZURICH SWITZERLAND 1. NORCE & the Bjerknes Centre; 2. École Normale Supérieure; 3. Met Office
Transcript of A physically-based method for classification of precipitation types …€¦ · classification of...
Aphysically-basedmethodforclassificationofprecipitationtypesandtheimplicationsforfuturechangesoverNorwayStefanSobolowski1;Basile Poujol1,2;SégolèneBerthou3;StevenChan3;Torge Lorenz1;Priscilla Mooney1
22 AUGUST, 2019 LATSISSYMPOSIUM, ETHZURICHSWITZERLAND
1.NORCE&theBjerknes Centre;2.École Normale Supérieure;3.MetOffice
Aphysically-basedmethodforclassificationofprecipitationtypesandtheimplicationsforfuturechangesoverNorwayStefanSobolowski1;Basile Poujol1,2;SégolèneBerthou3;StevenChan3;Torge Lorenz1;Priscilla Mooney1
16 OCTOBER, 2019 ICRC-CORDEXBEI J INGCHINASESSION A2
1.NORCE&theBjerknes Centre;2.École Normale Supérieure;3.MetOffice
MMoottiivvaattiioonn
Foto:AudunBraastad/NTBscanpix
WesternNorway:Flooding,multiplelandslides,200yr.rainfall[localmeasurements:92-108mm/24hr
Foto:JohnArneHolmlund /HA/NTBscanpix
EasternNorway: highintesnityshortdurationeventwipedoutroadsandcutoffresidents[localmeasurements:15-20mm/hrand40-55mm/3hr]
Threeofthetopfive24hrlocalraintotalsforwesternNorwayhaveoccurredin2019.• Eventsleadtoquestionsaboutfuturescenarios• Strongevidencethatmeanandextremesincreaseinawarming
climate• Wedon’tknowthespecifics• CPMcanhelp*
MMoottiivvaattiioonn
EarlierworkconfirmsexpectedincreasesinpreciptationwithCPM
Communitynowmovingbeyonddescriptionofresults(seeright)
Weaimforaphysicaldescriptionofchangesinprecipitationcharacteristics
And elucidatetheunderlyingprocesses
Figure 6fromBerthou etal.(2018)Illustrates the shifttolarger contribu-tions frommoderatetohigh intensityevents inJJA(focuson redandturquoiselines)
OOuuttlliinnee
Introduceaphysically-basedalgorithmforseparationofprecipitationtypesinCPMsimulations
Brieflyshowperformance
Futureprecipitationcharacteristicsfroma3kmPGWexperimentoverNorway
Discussmechanisms(preliminary)
Summary,limitations&thewayforward
AAllggoorriitthhmmffoorrsseeppaarraattiioonnooffpprreecciippiittaattiioonniinnccoommpplleexxtteerrrraaiinn
Aim1:classifyprecipitationtypesaccordingtophysicalprocessesAim2:dosoinarelativelysimpleframeworkwithcommonlyavailablevariables
Variables(hourly):Precipitation,Threedimensionalwindspeed(u,v,w)atthemiddleofthetroposphere(500hPa),Horizontalwindspeed(u,v)atalevelclosetotheground(700hPa),butabovemostofthetopographyinthedatasetdomain
Criteria:• Verticalvelocitycriterion• mid-troposphereverticalvelocitycriterion• orographicupliftverticalvelocitycriterion
• Potentialvorticity dipolescriterion
Poujol etal.(inrevision)
MMooddeellSSttuuffff
WRF3.9.1one-waynest15km,3km
Allconvectionturnedoffat3km
Thompsonmicrophysics
Presentdaysimulation:ERA-Interimdriven[1996-2005]+
Futuresimulation:PGWbasedonRCP8.5[2035-65]
AAllggoorriitthhmmppeerrffoorrmmaannccee::PPrreesseennttddaayy
GoodseparationineasternNorway
Notasgoodinwest(likelyduetomisclassificationinpresenceoforography)
Stillmuchbetterthanparameterization-basedseparation(ERA-Interim)
Relativeamountsaresimilar(percentages)
DistributioncurvesbasedonASoP methodsseeKlingaman etal.(2017)andBerthou etal.(2018)
AAllggoorriitthhmmppeerrffoorrmmaannccee::aanneexxaammpplleewwiitthhaabbiittooffeevveerryytthhiinngg
IInntteennssiittyy-- dduurraattiioonnpplloottssiinnddiiccaatteerroobbuussttsshhiiffttsswwiitthhddiissttiinnccttssppaattiiaallaannddsseeaassoonnaallffllaavvoorrss
WesternNorway Eastern Norway
AASSooPP pplloottsssshhoowwccoonnvveeccttiivveepprreecciippiittaattiioonnmmaakkeessllaarrggeessttccoonnttrriibbuuttiioonnttooaaccttuuaallcchhaannggee
Positiveallseasons;Shiftstowardshigherintensities
WesternNorway
Eastern NorwayInsummerprecipitationfrommoderateintensitiesdecreases
IInnffrraaccttiioonnaalltteerrmmsstthheecchhaannggeessccoommeeffrroommmmooddeerraatteettoohhiigghhiinntteennssiittiieess
WesternNorway
Eastern Norway
Convectiveandorographicprecipitationshowthesamepatternofshifting
Convectiveandorographicprecipitationshowthesamepatternofshifting
CCoommpplleexxiinntteerrppllaayyooffpprroocceesssseessddrriivveesstthheesseecchhaannggeess((wweetthhiinnkk))
Winterchangesarewellexplainedthermodynamics,consistentwiththeory(relativehumiditynearlyconstant,scalings asexpected)
SummerresponseineasternNorway(decreaseinlowtomoderaterates;largeincreaseinhighintensities)duetoincreaseinbothCAPEandCIN
Summer&FallwesternNorway(strongincreasesinbothconvectiveandorographic)CAPEandCINincreaseandRHincreases/efficiencydecreases(fallonly)maycontributetoapparentsupercc-scaling(seeextraslides)
Springresponsesgenerallyweakbutfrequencyofstratiform precipitationincreases.Why?
Microphysicalchangeslikelymatterasmeltinglevelshifts,RHincreases,IWCandLWCchangeasymmetric,decreasedefficiency(right)
SSuummmmaarryy
WesternNorway
Eastern Norway
• Arelativelysimplephysically-basedalgorithmseparatesprecipitationtypesinaCPM
• Thisallowsfordeeperunderstandingofchangingcharacteristicsofprecipitation
• Convectiveprecipitationincreasessubstantially
• Changescomefromshifttomoreintenserates(nearlyuniversal)
• Notallchangesareuniforminspaceortime(i.e.locationandseason)
• Physicalexplanationsalsovarydependingonseason&location
RReeffeerreenncceess
Berthou,S.,Kendon,E.J.,Chan,S.C.,Ban,N.,Leutwyler,D.,Schär,C.,&Fosser,G.(2018).Pan-Europeanclimateatconvection-permittingscale:Amodelintercomparison study.ClimateDynamics.https://doi.org/10.1007/s00382-018-4114-6
Klingaman,N.P.,Martin,G.M.,&Moise,A.(2017).ASoP (v1.0):Asetofmethodsforanalyzingscalesofprecipitationingeneralcirculationmodels.Geoscientific ModelDevelopment,10(1),57–83.https://doi.org/10.5194/gmd-10-57-2017
Poujol,B.,Sobolowski,S.,Mooney,P.&Berthou,S.(in- revision)Aphysically-basedprecipitationseparationalgorithmforconvection-permittingmodelsovercomplextopography.QuarterlyJournaloftheRoyalMeteorologicalSociety.
EExxttrraasslliiddeess::CCaavveeaattssaannddffuuttuurreeddiirreeccttiioonnss
Singlemodel,noshallowconvection,PGW(largely)ignoresdynamicalchanges,Algorithmcanbeimproved,etc.,etc.…
Applytomulti-modelensemblefromCORDEXFPS-Convection
ApplytoCPMsimulationsdrivenbyCMIP5/6tocapturelargescaledynamicalaspects
EExxttrraasslliiddeess::PPeerrcceennttaaggeecchhaannggeeaannddtteemmppeerraattuurreessccaalliinngg((tthheeoorryyvvss..ssiimmuullaattiioonn))
WEST EAST
Seasons DJF MAM JJA SON DJF MAM JJA SON
ΔT 1.7 1.7 1.8 1.9 2.2 1.8 1.9 2.2
EExxttrraa sslliiddeess::IIDDFFCCoonnvveeccttiioonn
EExxttrraa sslliiddeess::IIDDFFSSttrraattiiffoorrmm
EExxttrraa sslliiddeess::IIDDFFOOrrooggrraapphhiicc
