modeling terrestrial ecosystems: biogeophysics & canopy
TRANSCRIPT
Modelingterrestrialecosystems:Biogeophysics&canopyprocesses
NCARissponsoredbytheNa3onalScienceFounda3on
GordonBonanNa3onalCenterforAtmosphericResearch
Boulder,Colorado,USA
CLMTutorial2016Na3onalCenterforAtmosphericResearchBoulder,Colorado12September2016
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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)
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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
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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
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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)
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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)
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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
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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)
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Leafphysiologicalparameters
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Canopyconductance–gradientsofPAR
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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
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US-Ha1,July2001(DBF)CLM4.5
CLMml
ObsModel