GlobalPrecipitation—GPCP,TRMMandGPM

MeansandVariations

RobertAdler,Jian-Jian Wang,Guojun Gu,MattSapianoUniversityofMaryland

GeorgeHuffman,DaveBolvin,EricNelkinNASA/Goddard

Udo SchneiderGPCC/DWDRalphFerraro,Ping-PingXie NOAA

andothers

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Global Precipitation Climatology Project (GPCP)Climatology(1979-2015)

GPCPisanoften-usedanalysis basedonsatelliteandgaugedata(1979-nearpresent).NoTRMM,GPMorCloudsat dataareinthecurrentGPCP.

mm/d

Adleretal.,2003J.HydrometHuffmanetal.,2009GRL

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WebAddressforCurrentGPCPproducts:GPCP.umd.edu

� New GPCPMonthly(V2.3)beingproducedatUMDforNOAA’sClimateDataRecord(CDR) program

� Final analysisavailableafewmonthsaftertime;Interim CDR(ICDR)available~10daysafterendofmonthforreal-timeclimateanalysis

� V2.3Daily andPentad productsunderdevelopment

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GPCPNewV2.3vs.V2.2

�Differencesduetocross-calibrationerrors(SSMItoSSMISandTOVStoAIRS)overoceananduseofnewGPCC“Full”gaugeanalysis

� Biggestdifferenceafter2009(~1.8%overocean)� Regionallybiggestdifference40-60Noverocean

Land+Ocean

Land

Ocean

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CurrentGPCPgloballong-termnumberis2.69mm/d +/- ~7%Withtheerrorbasedonvariationsamongdifferentestimates(includingTRMM)

(Adleretal.2012JAMC)

Theseglobalnumbersandcontinental-scalevaluesfitwellwithlarge-scalewaterandenergybudgetstudies(e.g.,Rodell etal.2015J.Clim.)

But,howwelldotheseverylarge-scaleprecipitationnumberscomparewithTRMM,GPMandCloudSat?

AbsoluteMagnitudeofGlobal PrecipitationOcean Land Ocean+Land

Precipitation 2.90 mm/d 2.24 mm/d 2.69 mm/d *

*NewvaluesbasedonGPCPV2.3

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**Behrangi etal.,2014JClim

Tropical Mean(Ocean) RainfallEstimates

TRMM-based mean tropical oceanvalues agree well with GPCP and withTRMM PR/CloudSat value.

*Adleretal.2009JMSJ

HowdoTRMM-basedestimatesfitwithGPCP?

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GPCPPR+ CloudSat;AMSR+ CloudSat

60N-60S(ocean)

3.04mm/d

3.13[GPCP+~3%]

Behrangi etal.2014JClim

Global Mean(Ocean) RainfallEstimates

GPCPglobaloceannumberstillseemsreasonable.IftherearefaultsintheGPCPglobalprecipitationmagnitude(e.g.,underestimation)it

probablydoesn’thavetodowithlightrainorsnow,butperhapswithintenseconvectiverainfallinthetropics.

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� GPM somewhat higher than GPCPin tropics

� GPM lower in extra-tropics

Ocean

Version4ofGPMProducts

GPMTwo-YearPrecipitationfromPassiveMicrowave(GMI)andRadar(DPR)GPM

GPMCompositeMarch2014– Feb.2016

OceanZonalMean(March2014-Feb.2016)

GPCP

Equator

45° N

45° SGPCPArtifact

GPM

mm/d PMW Radar Comb GPCP25N-25S 3.50 3.63 3.37 3.3365N-65S 2.70 2.83 2.63 3.07

GPCPMarch2014– Feb.2016

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OceanZonalMean(March2014-Feb.2016)

GPCP

Equator

45° N

45° S

GPM

80N

80S

XXMeanValues(55-80NOcean)CloudSat GPCP

CloudSat GPCP

MeanValues(55-80NOcean)

XX

CloudSat HighLatitudeStudy

Behrangi etal,(2016)JGRMeanvaluesofprecipitation(rainplussnow)overfiveyears,55-80° latitude:

CloudSat-basedestimatesagreecloselywithGPCPmeans(overoceanandland);bothhigherthanGPM

GPMandCloudSat shouldbetheStandardstowhichGPCPistuned!

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VariationsinGlobal SurfaceTemperatureandPrecipitationTrends,Inter-decadalShiftsandENSOandVolcanoEffects

SurfaceTemperature:Trend:.15C/decadeENSO:0.2CamplitudeVolcano:0.4Camplitude

Precipitation:Trend:~zeroENSO:.05mm/d(2%)amplitude

9%/KVolcano:.09mm/d(3%)amplitude

8%/K

ClimateShift

GlobalSurfaceTemperature

GlobalPrecipitation(GPCP)

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WaterVapor Precipitation(GPCP)

Trends 10%/C(ocean) ~ 1 %/C(global)

Inter-annualENSO

15%/C(ocean) 9%/C(global)

Inter-annualVolcano

9%/C(ocean) 8%/C(global)

ComparisonofWaterVaporandPrecipitationChangesinRelationtoTemperatureChangesforInter-annualandTrendTimeScales

Precipitationvariationsvarydifferentlyfromwatervaporontrendscale,butaremuchmoresimilarforinter-annualscale—

forbothENSOandvolcanoes11

TRMM-based Sfc.Temp.-RainfallRelations(Activevs.PassiveMicrowave)1998-1999ElNinotoLaNinaTransition

RainfallAnomaly

(%)

SurfaceTemperatureAnomaly(°)

TRMMPassiveMicrowaveGPCPPassiveMicrowave

TRMMRadarNS,2km,4km

TRMMRadar6km

TRMMCombined

TRMMRadardoesnotconfirmPMWT-Rrelations—Attenuationissues?

Ocean

TRMM

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SurfaceTemperatureAnomaly(C)

RainfallAnomaly

(%)

GPM-based Sfc.Temp.-RainfallRelations(Activevs.PassiveMicrowave)2014-2016NeutraltoElNinoTransition

GPMPassiveMicrowave

GPCPPassiveMicrowaveGPMRadarNS,2km,4km

GPMCombined

GPMRadarbetterconfirmsPMWT-Rrelations—notclearwhydifferentfromTRMM?

GPMRadar6km

GPMRadar~13%/CTRMMRadar~0%/C

Ocean

GPM

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1. Satelliteerahasresultedinamatureviewofthemagnitudeanddistributionofprecipitationacrossourplanet,althoughthereisstillmuchtobedoneintermsofaccuracy,lengthofrecordandspaceandtimeresolutions.

2. Recentmissions(TRMM,Cloudsat,GPM)confirmearlierGPCPplanetaryclimatologicalmeanof~2.7mm/d withinerrorboundsof+/-7%.GPMmeanvaluesslightlyhigher(5-8%)inthetropics thanGPCPandTRMMnumbers,butlowerinhigherlatitudes (overocean).CloudSat confirmsGPCPmeanestimatesinhighlatitudes.

3. BasedonPMWretrievals,planetary-scalevariationsofprecipitationrelatedtoENSOandvolcanoes areevidentintherecord,althoughnosignificanttrendinglobalmeanprecipitation hasbeenfoundforthesatelliteera(1979-present).

1. GPMradarresultsfor2014-2016(includingElNino)betteragreewithsurfacetemperature– rainfallrelationsforPMWresults (includingGPCP)thandidTRMMradarresults.Reasonsforthisareunderinvestigation.

Summary

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ExtraSlides

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TrendsinGlobalPrecipitationDuringSatelliteEra(1979-2013)

EstimatedTrendsrelatedtoGlobalWarming

mm/d/decade

Although the trend in global total precipitation is nearzero (in GPCP analysis), the pattern of observedregional trends (left panel) is related to GlobalWarming (GW) plus inter-decadal signals such as PDOand AMO (ENSO impact is small). Bottom left panelshows trend pattern after PDO effect is removed, abetter estimate of of GW impact on precipitationregional trends and also a pattern closer to thatpredicted by CMIP climate models (bottom right), butwith smaller magnitudes—by factor of 2-3.

Gu,AdlerandHuffman(2016)ClimateDynamics

ObservedTrends(GPCP)

TrendsfromCMIPensemble

EstimatedTrendDistributionforSatelliteEraduetoGlobalWarming

Climatology

Wetgettingwetteranddrygettingdrierinmostareaswithafewexceptions

Trend

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TrendsinPrecipitation(1900-2010)duetoGlobalWarming[withaerosoleffecttakenout]

Gaugesoverland;“reconst-ruction”overwater

ClimatemodelforcedbyobservedSST,etc.

ClimatemodelforcedbyCO2

Composite,i.e.,meanofthethreeotherfields

Gu andAdler(2015)J.Clim.

“RECONS”isareconstructionofglobalprecipitationbySmithetal.(2012)J.Atmos.Oceanic Tech. 19