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