evalua&ng the mjo forecast skill in the ncep gefs 35-day ... · evalua&ng the mjo forecast...
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Evalua&ngtheMJOforecastskillintheNCEPGEFS35-dayExperiments
WeiLi,
YuejianZhu,XiaqiongZhou,MalaquiasPeña,DingchenHou,HongGuan,EricSinskyChristopherMelhauser,RichardWobus
NOAA/NCEP/EMCandIMSG
Presenta)onforCWBDecember202017
Outline
• Background
• ExperimentsandData
• MJOforecastskill
• ForecastskillofthekeycomponentsofMJO
• DependenceofMJOskillonensemblesize
• Summary
Eachensemblememberevolu)onisgivenbyintegra)ngthefollowingequa)onwhere ej(0) is the ini)al condi)on, Pj(ej,t) represents the model tendencycomponent due to parameterized physical processes (model uncertainty), dPj(ej,t) represents random model errors (e.g. due to parameterized physicalprocessesorsub-gridscaleprocesses–stochas)cperturba)on)andAj(ej,t)istheremaining tendency component (different physical parameteriza)on or mul)-model).Reference:-firstglobalensemblereviewpaperBuizza,R.,P.L.Houtekamer,Z.Toth,G.Pellerin,M.Wei,Y.Zhu,2005:"A Comparison of the ECMWF, MSC, and NCEP Global Ensemble PredicBon Systems“MonthlyWeatherReview,Vol.133,1076-1097
∫=
++++=T
tjjjjjjjj dtteAtedPtePdeeTe
00 )],(),(),([)0()0()(
Description of the ensemble forecast system
Opera&on:ECMWF-1992;NCEP-1992;MSC-1998
Ini&aluncertainty Modeluncertainty
Background
3
CRPSSforNH500hPageopoten&alheight
6days
10days17years
ExperimentsandData• Opera)onalVersion:
o GEFSv11extendedto35dayforecast(STTP);o T574(33km)for0-8days,T382(55km)aaer8days.
• Experiments:o SPPT+SHUM+SKEB(SPs)withcontrolversionofSST;o SPswithbiascorrectedCFSv2forecastSST(SPs+CFSBC);o SPswithbiascorrectedCFSv2forecastSSTandscaleawareconvec)on
scheme(SPs+CFSBC+CNV);
Allexperimentcovertheperiodof20140501-20160526,5-dayinterval.
• Analysisdata:o GDASduring20140101-20161031;NCEPreanalysisforUandNOAAOLR.
• Bothforecastandanalysisdatausingdailymean
1)Stochas&cSchemesforAtmosphere-AppliedtoGEFSexperiments
• Dynamics:Duetothemodel’sfiniteresolu)on,energyatnon-resolvedscalescannotcascadetolargerscales.– Approach:Es)mateenergylosteach)mestep,and
injectthisenergyintheresolvedscales.a.k.astochas)cenergybackscajer(SKEB;Berneretal.2009)
• Physics:Subgridvariabilityinphysicalprocesses,alongwitherrorsintheparameteriza)onsresultinanunderspreadandbiasedmodel.– Approach:perturbtheresultsfromthephysical
parameteriza)ons,andboundarylayerhumidity(Palmeretal.2009),andinspiredbyTompkinsandBerner2008,wecallitSPPTandSHUM
• AboveschemeshasbeentestedforcurrentoperaBonalGEFS(spectrummodel)withposiBveresponse–plantoreplaceSTTPfornextimplementaBon(FV3GEFS)
Berneretal.(2009)
Kine)cEnergySpectrum
∞k-5/3∞k-3
k
6
Examplesofstochas&cpafernsforSPPT
CourtesyofDr.BingFu
[ ] tc
tttc
ta
tf SSTeSSTSSTSST +−= −− 90/)0(00
[ ] )]([**)1( _00 t
cfsrctccfs
tcfs
tcfsrc
tcfsrc
ta
tf SSTSSTSSTwSSTSSTSSTwSST −−++−−=
• Opera&onal
2).SSTSchemes(opera&on)and2-&erSSTapproach-Assimilatecoupling
• CFSBC
tcSST --ClimatologicaldailySSTfromRTGanalysisforforecastlead-)mettcfsSST --CFSpredic)veSST(24hrmean)forforecastlead-)met
tccfsSST _ --CFSmodelclimatology(predic)veSST)forforecastlead-)met
0taSST --SSTanalysisatini)al)me(RTG)
tcfsrcSST --CFSreanalysisdailyclimatologyforforecastlead-)met
w(t) = (t − t0 )35
3).UpdateGFSconvec&onscheme• Scale-aware,aerosol-awareparameteriza&on• Rainconversionratedecreaseswithdecreasingair
temperatureabovefreezinglevel.• Convec&veadjustment&meindeepconvec&on
propor&onaltoconvec&veturn-over&mewithCAPEapproachingzeroaieradjustment&me.
• Cloudbasemassfluxinshallowconvec&onschemefunc&onofmeanupdraivelocity.
• Convec&veinhibi&on(CIN)inthesub-cloudlayeraddi&onaltriggercondi&ontosuppressunrealis&callyspofyrainfallespeciallyoverhighterrainsduringsummer
• Convec&vecloudinessenhancedbysuspendedcloudcondensateinupdrai.
• SignificantimprovementespeciallyCONUSprecipinsummer.
9
12-36hrfcst
CourtesyofDr.VijayTallapragadaReference:Han,J.andetal.,2017Wea.andFcst.
Akeyarea()mescale)tofocuson…
EnsembleandStochas&c
perturba&onontropicalarea
Atmosphere-ocean
interac&on
Tropicalconvec&onsincludecloud,radia&on,
precipita&onandetal.
Exampleof8MJOphaseswithcompositeoftwomodes(RMM1andRMM2)
RMM1–Enhancedconvec)onovermari)mecon)nentRMM2–Enhancedconvec)onoverPacificocean
12
Evalua&onofMJOskillsBasedonWheeler-HendonIndex
Animprovementcomesfromthreeareas:
1.Ensembleandstochas)cphysicperturba)ons2.2-)erSSTtoassimilateimpactofcoupling3.Newscale-awareconvec)vescheme
AmplitudeofMJOduringMay2014-May2016fromGDASanalysisdata.Theresolu)onofthe)me-seriesis5days
CourtesyofDr.QinZhang
6-yearaverageWH-MJOforecastskillsforCFSv2
16
17days
17
WH-MJOForecastSkillsfor2-yrExperiments
RMM2
RMM1+RMM2
RMM1
12.5days
22days
CFSv2isNCEPoperaConalclimateforecastsystem(coupling)implementedon2011–16membersleg(24hours)ensemble
GEFSweek3&4forecasts(May2014-May2016)
HowaboutMJOskillofcouplingmodel?
StrongvsWeakPeriod
For“strong”and“weak”periods(rela&vely),ourbestconfigura&on(SPs+CFSBC+CNV)
24-days
VariabilityoftheMJOindexLeadday=15
Leadday=22
-----Analysis-----STTP(CTL)-----SPs-----SPs+CFSBC-----SPs+CFSBC+CNC
1. CTLforecastsaremuchstronger
2. Biasesaresimilarfromdifferentleads
3. Biasesarevariedfordifferentexperiments
MJOevoluCon20150501-20150716
lead1 lead8 lead15 lead22
20151001-20160106
GDAS STTP SPs SPs_CFSBC SPs+CFSBC+CNV
NOAA GDAS STTP SPs
SPs+CFSBC SPs+CFSBC+CNV
MJOpropaga&on:leadday=1
NOAA GDAS STTP SPs
SPs+CFSBC SPs+CFSBC+CNV
MJOpropagaCon:leadday=15
OLRanomalyNopropaga&on:Systema&cerrorVariabilityofconvec&on
NOAA GDAS STTP SPs
SPs+CFSBC SPs+CFSBC+CNV
MJOpropaga&on:leadday=22
Nopropaga&on:Systema&cerrorVariabilityofconvec&on
ForecastskillofthekeyVariablesU200anomaly
U850anomaly OLRanomaly
Muchimprovementforzonalwinds–circula)on;butnotmuchforOLR
U850 U200 OLR
CorrelaConmapofthekeyVariables
Leaddays=15Indiaocean W.Pacific
U850 U200 OLR
CorrelaConasafuncConofleadCme
CTL
SPs-CTL
SPs+CFSBC-CTL
SPs+CFSBC+CNV-CTL
U850 U200 OLR
PaRerncorrelaConofthecompositevariablesinMJOphases
MJOpha
se
Lead&me
Phase3–IndiaOcean
Phase6–W.Pacific
CORRasafunc&onoflead&me:APCP
EffectoftheSPsT U RH
20160301-20160326(6casesaverage)
SPs–bigimprovementofMJOskills;goodspread,smallerbiasintropical
31
WH-MJOForecastSkills:Ensemblemeanvseachmember
5-memebrs11-memebrs21-memebrs
ThisstudybasedonSPsconfiguraCononly!!!
Summary
• MJOforecastskill:SPs+CFSBC+CNV(22days)>SPs+CFSBC(18.5days)>SPs(16.8days)>STTP(12.5days)
• ComponentForecastskill:U200>U850>OLR
• MostevidentimprovementoccursoverthetropicalwestPacificandIndianOcean.
• MJOskillof21memberissimilarto11memberandboth21and11memberskillisbeferthan5memberskill
• MJOpropaga&on–couldrelateseveralissues,suchasmodelphysics–tropicalconvec&on?
BackupSlides
24hrAPCP(Leadday=7),2yrave.
DifferenceMaps
24hrAPCP(Leadday=14),2yrave.
DifferenceMaps
24hrAPCP(Leadday=21),2yrave.
DifferenceMaps
20140501-20160630,Daily 20140501-20160526,5d