Modeling terrestrial ecosystems: Biogeophysics & canopy

Modelingterrestrialecosystems:Biogeophysics&canopyprocesses

NCARissponsoredbytheNa3onalScienceFounda3on

GordonBonanNa3onalCenterforAtmosphericResearch

Boulder,Colorado,USA

CLMTutorial2016Na3onalCenterforAtmosphericResearchBoulder,Colorado12September2016

2

RoleoflandsurfaceinEarthsystemmodels

•  Providesthebiogeophysicalboundarycondi3onsattheland-atmosphereinterface–  e.g.albedo,longwaveradia3on,turbulentfluxes(momentum,sensibleheat,latent

heat,watervapor)•  Par33onsavailableenergy(netradia3on)atthesurfaceintosensibleandlatentheatflux,

soilheatstorage,andsnowmelt

•  Par33onsrainfallintorunoff,evapotranspira3on,andsoilmoisture–  Evapotranspira3onprovidessurface-atmospheremoistureflux–  Riverrunoffprovidesfreshwaterinputtotheoceans

•  Providesthecarbonfluxesatthesurface(photosynthesis,respira3on,fire,landuse)•  Updatesstatevariableswhichaffectsurfacefluxes

–  e.g.snowcover,soilmoisture,soiltemperature,vegeta3oncover,leafareaindex,vegeta3onandsoilcarbonandnitrogenpools

•  Otherchemicalfluxes(CH4,Nr,BVOCs,dust,wildfire,drydeposi3on)•  Landsurfacemodelcostisactuallynotthathigh(~10%offullycoupledmodel)

3

Thelandsurfacemodelsolves(ateach3mestep)Surfaceenergybalance(andotherenergybalances,e.g.incanopy,snow,soil)

S�+L�=S�+L�+�E+H+G§  S�,S�aredown(up)wellingsolarradia3on§  L�,L�aredown(up)wellinglongwaveradia3on§  �islatentheatofvaporiza3on,Eisevapotranspira3on§  Hissensibleheatflux§  Gisgroundheatflux

Surfacewaterbalance(andotherwaterbalancessuchassnowandsoilwater)

P=(ES+ET+EC)+(RSurf+RSub-Surf)+∆SM/∆t§  Pisrainfall§  ESissoilevapora3on,ETistranspira3on,ECiscanopyevapora3on§  RSurfissurfacerunoff,RSub-Surfissub-surfacerunoff§  ∆SM/∆tisthechangeinsoilmoistureovera3mestep

Carbonbalance(andplantandsoilcarbonpools)

NPP=GPP–Ra=(∆Cf+∆Cs+∆Cr)/∆tNEP=NPP–RhNBP=NEP–Fire–LandUse§  NPPisnetprimaryproduc3on,GPPisgrossprimaryproduc3on§  Raisautotrophic(plant)respira3on,Rhisheterotrophic(soil)respira3on§  ∆Cf,∆Cs,∆Crarefoliage,stem,androotcarbonpools§  NEPisnetecosystemproduc3on,NBPisnetbiomeproduc3on

RoleoflandsurfaceinEarthsystemmodels

4

Couplingwiththeatmosphereeverymodel3mestepisafundamentalconstraint(<30minute3mestep)Soistheneedtorepresentthegloballandsurface,includingAntarc3ca,theTibetanPlateaualongwithforests,grassland,croplands,tundra,desertscrubvegeta3on,andci3es

Conserva3onofenergyandmassisrequired

Westrivetodevelopaprocess-levelunderstandingacrossmul3pleecosystemsandatmul3ple3mescales(instantaneous,seasonal,annual,decadal,centuries)

Modeldesignphilosophy

Top-down,empiricalmodeling

1016 12 30a

pL N TE I

⎛ ⎞⎛ ⎞ ⎛ ⎞⎜ ⎟⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠

=

Thornthwaite:Monthlypoten3alevapotranspira3ondrivenbyairtemperature

np

RsEs

α γ λ=+

Priestley–Taylorequa3on:Dailypoten3alevapotranspira3ondrivenbyradia3on

1 2 3( ) ( ) ( )GPP S f T f f VPDε θ= ↓

Produc3onefficiencymodeldrivenbyradia3onandempiricalscalars

Penman-Monteithequa3onFvCBphotosynthesismodelBall-BerrystomatalconductancemodelFick’slawofdiffusionDarcy’slawandRichardsequa3on(soilwater)Fourier’slaw(heatconduc3on)

3000 ,1 exp(1.315 0.119 )

min 3000 1 exp( 0.000664 )T

NPP P⎡ ⎤⎢ ⎥⎣ ⎦

⎧ ⎫⎨ ⎬+ −⎩ ⎭

= − −

AnnualNPPdrivenbytemperatureandprecipita3on

Processmodeling

5

Lackofacommonlanguage

Fluxispropor3onaltothedrivingforce:Flux=propor3onalityconstant*gradientofdrivingpoten3alDescribesheatflowinsoil(Fourier’slaw),waterflowinsoil(Darcy’slaw),turbulentfluxes(Fick’slaw)

( )w s aE C u q qρ β= −

( )s a

a s

q qE

r rρ −

=+

( )ps a w

cE e e gλ

γ= −

( )s a wE q q g= −

Atmosphericmodels:

kgm–2s–1

Landsurfacemodels:

Dimensionlessdragcoefficient

ms–1 kgkg–1kgm–3

Dimensionlesssoilmoisturefactor

resistance(sm–1)

Biometeorology:

ms–1Pa

Plantphysiology:

molm–2s–1 molmol–1 molm–2s–1

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Modelnamedependsondiscipline:Atmosphericscienceslandsurfacemodelsoil–vegeta3on–atmosphere–transfermodelHydrologyhydrologicmodel(SVATwithlateralfluxes)Ecologybiogeochemicalmodeldynamicglobalvegeta3onmodelecosystemdemographymodel

Modelname

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TheCommunityLandModel

Olesonetal.(2013)NCAR/TN-503+STR(420pp)

Lawrenceetal.(2011)J.Adv.Mod.EarthSyst.,3,doi:10.1029/2011MS000045

Lawrenceetal.(2012)JClimate25:2240-2260

Surfaceenergyfluxes Hydrology Biogeochemistry

Landscapedynamics

Temporalscale§  30-minutecouplingwithatmosphere§  Seasonal-to-interannual(phenology)§  Decadal-to-century(disturbance,landuse,succession)

§  Paleoclimate(biogeography)

SpaSalscale1.25°longitude�0.9375°la3tude(288�192grid),~100km�100km

Fluxesofenergy,water,CO2,CH4,BVOCs,andNrandtheprocessesthatcontrolthesefluxesinachangingenvironment

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Themodelsimulatesacolumnextendingfromthesoilthroughtheplantcanopytotheatmosphere.CLMrepresentsamodelgridcellasamosaicofupto5primarylandunits.Eachlandunitcanhavemul3plecolumns.Vegetatedlandisfurtherrepresentedaspatchesofindividualplantfunc3onaltypes

Glacier16.7%

Lake16.7%

Urban8.3%

Vegetated50%

Sub-gridlandcoverandplantfunc3onaltypes

Crop8.3%

1.25oinlongitude(~100km)

0.9375

o inla3tud

e(~100km

)

Landsurfaceheterogeneity

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Surfaceenergybalanceandsurfacetemperature

Surfaceenergybalance:(S�-S�)+�L�–�σTs4–H[Ts]–�E[Ts]=soilheatstorage

Withatmosphericforcingandsurfaceproper3esspecified,solvefortemperatureTsthatbalancestheenergybudget

AtmosphericforcingS�-Solarradia3on(vis,nir;direct,diffuse)L�-Longwaveradia3onTa-airtemperatureqa-atmosphericwatervaporu-windspeedP-surfacepressure

SurfaceproperSesS�-reflectedsolarradia3on(albedo)�-emissivitygah-aerodynamicconductance(roughnesslength)gc-surfaceconductancek-thermalconduc3vitycv-soilheatcapacity

( )s a ahp T T gH c −=

( )*1 1

[ ]s a

ah c

q T qg g

Eλ λ − −

−+

=

Sensible heat

Ta

Ts

gah

Flux=Δconcentra3on*conductance

vT Tct z z

κ∂ ∂ ∂⎛ ⎞= ⎜ ⎟∂ ∂ ∂⎝ ⎠

Soilheatstorage:

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Turbulentfluxes–logarithmicprofiles

*

0

( ) ln ( )mu z du zk z

ψ ζ⎡ ⎤⎛ ⎞−= −⎢ ⎥⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦

Logarithmicwindprofileinatmospherenearsurface

withz0roughnesslength,ddisplacementheight,andψ(ζ) corrects for atmospheric stability

*

0

*

0

( ) ln ( )

( ) ln ( )

s hh

s wh

z dzk z

q z dq z qk z

θθ θ ψ ζ

ψ ζ

⎡ ⎤⎛ ⎞−− = −⎢ ⎥⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦⎡ ⎤⎛ ⎞−− = −⎢ ⎥⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

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Turbulentfluxes–logarithmicprofiles

*

0

( ) ln ( )mu z du zk z

ψ ζ⎡ ⎤⎛ ⎞−= −⎢ ⎥⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦

withz0roughnesslength,ddisplacementheight,andψ(ζ) corrects for atmospheric stability

*

0

*

0

( ) ln ( )

( ) ln ( )

s hh

s wh

z dzk z

q z dq z qk z

θθ θ ψ ζ

ψ ζ

⎡ ⎤⎛ ⎞−− = −⎢ ⎥⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦⎡ ⎤⎛ ⎞−− = −⎢ ⎥⎜ ⎟⎢ ⎥⎝ ⎠⎣ ⎦

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

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Plantcanopies

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

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Sunlit ShadedTs

Ta

Tg

Tv

Trad

H,λE,E,τx,τyL↑,albedo

Deardorff(1978)JGR83C:1889-1903Dickinsonetal.(1986)NCAR/TN-275+STRDickinsonetal.(1993)NCAR/TN-387+STR

CLMperspecSveofthelandsurface

T2m“Big-leaf”canopywithoutver3calstructure

“Surface”isanimaginaryheight(wherewindspeedextrapolatestozero)

FluxtoatmosphereusesMOST

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RadiaSvetransfer

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

15

CLMusesthetwo-streamapproxima3on(Dickinson,Sellers)

Two-streamradiaSvetransfer

( ) 0 ,1 1 bK xd d b sky b

dI K I K I K I edx

β ω βω β ω↑

−↑ ↓ ↓= − − − −⎡ ⎤⎣ ⎦l l l

( ) ( )0 ,1 1 1 bK xd d b sky b

dI K I K I K I edx

β ω βω β ω↓

−↓ ↑ ↓= − − − + + −⎡ ⎤⎣ ⎦l l l

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Howdowescalefromleaftocanopy?

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Leaftemperatureandfluxes

Leafenergybalance:

Withatmosphericforcingandleafproper3esspecified,solvefortemperatureTℓthatbalancestheenergybudget

AtmosphericforcingQa-radia3veforcing(solarandlongwave)Ta-airtemperatureqa-watervapor(molefrac3on)u-windspeedP-surfacepressure

LeafproperSes�ℓ-emissivitygbh-leafboundarylayerresistancegℓ-leafresistancetowatervaporcL-heatcapacity

( ) ( )4*2 2L a p a bh a

Tc Q T c T T g q T q gt

ε σ λ∂ = − + − + −⎡ ⎤⎣ ⎦∂l

l l l l l

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Leafboundarylayer

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

19

Stomatalgasexchange

Photosynthetically Active Radiation

Guard Cell Guard Cell

CO2 H2O

Moist Air

CO2 + 2 H2O � CH2O + O2 + H2O light

Chloroplast Low CO2

Stomata Open: •  High Light Levels •  Moist Leaf •  Warm Temperature •  Moist Air •  Moderate CO2 •  High Leaf Nitrogen

Leaf Cuticle

Photosynthesis Transpiration

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

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Stomatalconductance

Scalebar50µm

0 1s n s sg g g A h c= +

Ball-Berrystomatalconductancemodel Stomataop3mizephotosynthe3ccarbon

gainperunittranspira3onwaterlosswhilepreven3ngleafdesicca3on

n s sA D gιΔ ≤ Δ minl lψ ψ>Williamsetal.(1996)PlantCellEnviron.19:911-927

andEmpiricalrela3onshipbetweenstomatalconductanceandphotosynthesisandisappliedseparatelytosunlitcanopyandshadedcanopy

Op3miza3ontheory

Bonanetal.(2014)Geosci.ModelDev.7:2193-2222

21

min( , )n c j dA A A R= −

RuBPregenera3on-limitedrateis

rubisco-limitedrateis

wcistherubisco-limitedrateofphotosynthesis,wjislight-limitedrateallowedbyRuBPregenera3on

Farquhar,vonCaemmerer,Berryphotosynthesismodel

Leafphotosynthesis

( )*4( 2 )*

i

ji

J cA c−Γ= + Γ

max( )*(1 / )

c i

ci c i o

V cA c K o K−Γ= + +

Bonan(2016)EcologicalClimatology,3rded(CambridgeUniv.Press)

22

Leafphysiologicalparameters

23

Canopyconductance–gradientsofPAR

24

Sunlitandshadedcanopy

SUNLIT

SHADEDDepthinCanop

y

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Nitrogenprofile

DeclineinfoliageN(perunitarea)withdepthincanopyyieldsdeclineinphotosynthe3ccapacity(Vcmax,Jmax)

Bonanetal.(2011)JGR,doi:10.1029/2010JG001593

( ) bK xsunf x e−=

( ) ( )max25 max250

(sun)L

c c sunV V x f x dx= ∫

( ) ( )max25 max250

(sha) 1L

c c sunV V x f x dx= −⎡ ⎤⎣ ⎦∫

( ) ( )max25 max25 0 nK xc cV x V e−=

Note:CLM5hasamorecomplexcanopyop3miza3on

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Plantcanopyasa“bigleaf”

Ts

Ta

2gb

ei=e*(Ts) gb gs

ea

es

ci gb/1.4 gs/1.6

ca

cs

Stomata Leaf

Boundary Layer

Ts

Tac Ta

2gb*L ga

ei=e*(Ts) gb*L ga gs*L

eac ea

es

ci ca

cs

Canopy Atmosphere

Surface Layer

Mostmodelsusetwo-leaves(sunlitandshaded)

gb/1.4 *L gs/1.6 *L

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Bonanetal.(1997)JGR102D:29065-75

Model

Observa3ons

BorealEcosystemAtmosphereStudy(BOREAS)1990s:singlesitecomparison,shortintensiveobservingperiod

Fluxtowers&modelvalidaSon

Fluxtowers&modelvalidaSon28

Stöcklietal.(2008)JGR,113,doi:10.1029/2007JG000562

CLM3.0–drysoil,lowlatentheatflux,highsensibleheatfluxCLM3.5–we�ersoilandhigherlatentheatflux

MorganMonroeStateForest,Indiana

2000s:annualcycle,mul3-sitecomparison(borealtotropical)

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FLUXNET-MTEdatafromMar3nJungandMarkusReichstein(MPI-BGC,Jena)

Radia3vetransfer

andphoto-synthesis

Control

CLM4overesSmatesGPP.ModelrevisionsimproveGPP.SimilarimprovementsareseeninevapotranspiraSon

Radia3vetransferforsunlitandshadedcanopy

117PgCyr-1 165PgCyr-1

130PgCyr-1

Bonanetal.(2011)JGR,doi:10.1029/2010JG001593

155PgCyr-1

Fluxtowers&modelvalidaSon

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Improvedannuallatentheatflux

ModelimprovementsreduceETbiases,especiallyintropics,andimprovemonthlyfluxes

Bonanetal.(2011)JGR,doi:10.1029/2010JG001593

65x103km3yr-1 68x103km3yr-1

65x103km3yr-1

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MorganMonroeStateForest

Stöcklietal.(2008)JGR,113,doi:10.1029/2007JG000562

drysoil,lowlatentheatfluxCLM3

CLM3.5

Waterstorage(m

m)

GRACECLM3CLM4

D.Lawrenceetal.(2012)JClimate25:2240-2260

Tower

Mississippibasin

Modelingacrossscales

Global

Bonanetal.(2011)JGR,doi:10.1029/2010JG001593

Largebasin

Annuallatentheatflux

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Researchareas

SurfacefluxesRoughnesssublayer,mul3layercanopiesRadiaSvetransfer3Dstructure,canopygapsPhotosynthesisTemperatureacclima3on,CO2response,product-limitedrate,C4plantsStomatalconductanceSoilmoisturestress,WUEop3miza3on,CO2responseCanopyscalingOp3maldistribu3onofnitrogen

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Canopyturbulenceandtheroughnesssublayer

CLM(andmostothermodels)useMOST,whichfailsaboveandwithinplantcanopies

Harman&Finnigan(2007)Boundary-LayerMeteorol.123:339-363Harman&Finnigan(2008)Boundary-LayerMeteorol.129:323-351

MOST

Obs

ProfilesfromtheCSIROfluxsta3onnearTumbarumba

RSL MOST

RSL

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Twowaystomodelplantcanopies

PhotographsofMorganMonroeStateForesttowersiteillustratetwodifferentrepresenta3onsofaplantcanopy:asa“bigleaf”(below)orwithver3calstructure(right)

SUNLIT

SHADEDDepthinCanop

y

SUNLIT

SHADEDDepthinCanop

yBig-leafcanopy§  Two“big-leaves”(sunlit,shaded)

§  Radia3vetransferintegratedoverLAI(two-streamapproxima3on)

§  Photosynthesiscalculatedforsunlitandshadedbig-leaves

MulSlayercanopy§  Explicitlyresolvessunlitandshadedleavesateachlayerinthecanopy

§  Light,temperature,humidity,windspeed,H,E,An,gs,ψL

§  Newopportuni3estomodelstomatalconductancefromplanthydraulics(gs,ψL)

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US-Ha1,July2001 US-Var,March2006

Mid-dayMid-day

Model

CLM4.5

CLMml

FricSonvelocity(momentumflux)

Obs

36

US-Ha1,July2001(DBF)CLM4.5

CLMml

ObsModel