modelling of the carbon cycle in the geoland project … · modelling of the carbon cycle in the...
TRANSCRIPT
Integrated GMES Project on Landcover and Vegetation
geoland
MODELLING OF THE CARBON CYCLE IN THE GEOLAND PROJECT
Jean-Christophe Calvet – Météo-France – ECMWF Seminar – 06.09.2005Co-funded by the European Commission within the GMES initiative in FP-6
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Contents
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
• Overview of geoland/ONC
• Models used in geoland/ONCISBA-A-gs / C-TESSEL (Météo-France / ECMWF)ORCHIDEE (LSCE)
• Representation of land surface patchiness
• VALIDATION: LAIFaPARwater flux comparison with operational modelsground based flux measurementscrop production
• Data Assimilation
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Overview
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
The geoland project
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Overview
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
The Observatory of Natural Carbon Fluxes of geoland
Partners
• Research partners: KNMI, LSCE, ALTERRA
• Service providers: ECMWF, Météo-France
• Associated user: LSCE
Objectives• Kyoto protocol
• Transpose the tools used for weather forecast to the monitoring of vegetation and of natural carbon fluxes:
Near real-time monitoring at the global scale (ECMWF) based on modelling,in situ data,assimilation of satellite data.
• Scientific validation of the system
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Overview
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
The products
• The terrestrial biospheric CO2 flux at the soil-vegetation-atmosphere interface• The water flux at the soil-vegetation-atmosphere interface• The vegetation biomass• The leaf area index• The root-zone soil moisture• The carbon storage.
SPATIAL RESOLUTION: ½ degree
The anthropogenic fluxes are not accounted for here: to be treated in atmospheric analysis projects (e.g. GEMS).The fluxes produced by geoland will be used by GEMS.
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Overview
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Root-zonesoil moisture
Vegetation Biomass(above-ground green
and wood)
Leaf Area IndexCarbon storage
(soil)
CO2 Flux Water Flux
STRONG PHYSICAL LINKS BETWEEN THE PRODUCTS:All these quantities interact and need to be fullyconsistent, i.e. produced at the same time by a physically-based model
The products
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Overview
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Usefulness of remote sensing data
• Land use maps (e.g. ECOCLIMAP)
• Analysis of the above-ground biomass by assimilation
• Model error Bias reduction• Atmospheric forcing Precipitation + Radiation• Model parameters Assimilation • Scalingissues Tiling
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Overview
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Maturity
• Assimilation of Ta & qa to analyse soil moisture already operational at ECMWF and Météo-France
• Assimilation of NDVI to analyse vegetation biomass is well advanced at LSCE
• ELDAS FP5 project
• New versions of operational land surface models are able to simulate the CO2fluxes
•Modelling: ISBA-A-gs at Météo-France, ORCHIDEE at LSCE, both involved in the PILPS-Carbon international intercomparison exercise
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
RRnn
RRGG
RRATAT
Rn=RGL-RCL=H+LE+G
RRTT
GG
LELEHHRRnn
RRGG
RRATAT
Rn=RGL-RCL=H+LE+G
RRTT
GG
LELEHH
GG
LELEHH
GGGG
LELEHH LELEHH
Land-surface modelling: the energy budget
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
PrecipitationPrecipitation
RunoffRunoff
DrainageDrainage
∆W = P – R – Dr - E
Soil moisture(W)
InterceptionInterception
TranspirationTranspirationPrecipitationPrecipitation
RunoffRunoff
DrainageDrainage
∆W = P – R – Dr - E
Soil moisture(W)
InterceptionInterception
TranspirationTranspirationPrecipitationPrecipitation
RunoffRunoff
DrainageDrainage
∆W = P – R – Dr - E
Soil moisture(W)
InterceptionInterception
TranspirationTranspiration
Land-surface modelling: the water budget
Transpiration
Photosynthesis
Respiration
Photosynthesis/Transpiration
The stomatal aperture controls the ratio:
according to the environment conditionsLight, temperature, air humiditysoil moisture atmospheric [CO2]
qa Ta
qs Ts
H20
Ci
Cs
Ca CO2
PAR
Glucides
qsat
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Land-surface modelling: the role of stomatal control
stomatestomate
,
10µ
m
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
ISBA-A-gs (Calvet et al. 1998-2004, Gibelin et al. 2005)A new version of the operational SVAT of Météo-France
C-TESSEL (Voogt et al. 2005)A new version of the operational SVAT of ECMWF, based on ISBA-A-gs
ORCHIDEE (Krinner et al. 2005)A research dynamic vegetation model with a high level of complexity
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
ISBA-A-gs / C-TESSEL
Met. forcing LAI
LE, H, Rn, W, Ts…
Active Biomass
CO2 Flux[CO2]atm
ISBA / TESSEL
Met. forcing LAI
LE, H, Rn, W, Ts…
ISBA-A-gs / C-TESSEL are CO2-responsive land surface models, new versions of operational schemes used in atmospheric models
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
ORCHIDEE is a research dynamic global vegetation model
STOMATESTOMATE SECHIBASECHIBAEnergy budget
Hydrology+
Photosynthesis
Vegetation and soilCarbon cycle
LMDZLMDZGeneral C irculation Model
LAI,roughness,albedo
Soil profiles ofw ater and tem perature,GPP
rainfall,tem perature, solar radiation, CO2 concentration...
Sensible and latent heat fluxes,albedoroughness, surface tem perature, CO2 flux...
DynamicVegetation Model
NPP, biom ass,litterfall ...
Vegetation typesbiom ass
ORCH IDEE
Biosphere
LPJLPJ
Atm osphere
Prescribed or calculated by
∆ t=1 h o ur∆ t=1 d a y
∆ t=1 ye arPrescribed or calculated by
Meteorological variables
Vegetation distribution
Prognostic phenology and allocation
STOMATESTOMATE SECHIBASECHIBAEnergy budget
Hydrology+
Photosynthesis
Vegetation and soilCarbon cycle
LMDZLMDZGeneral C irculation Model
LAI,roughness,albedo
Soil profiles ofw ater and tem perature,GPP
rainfall,tem perature, solar radiation, CO2 concentration...
Sensible and latent heat fluxes,albedoroughness, surface tem perature, CO2 flux...
DynamicVegetation Model
NPP, biom ass,litterfall ...
Vegetation typesbiom ass
ORCH IDEE
Biosphere
LPJLPJ
Atm osphere
Prescribed or calculated by
∆ t=1 h o ur∆ t=1 d a y
∆ t=1 ye arPrescribed or calculated by
Meteorological variables
Vegetation distribution
Prognostic phenology and allocation
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Photosynthesis
• SVAT approach (time step = minutes)
• Biochemical approach (explicit simulation of photosynthesis): Jacobs et al. 1996
• Big-leaf but radiative transfer within the canopy for photosynthesis and stomatal conductance
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Photosynthesis
Other global models using a biochemical approach:
SiB2 (Sellers et al. 1996)IBIS (Foley et al. 1996)BATS (Dickinson et al. 1998)MOSES (Cox et al. 1998-2001)BETHY (Knorr 2000)ORCHIDEE (Krinner et al. 2005)
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Soil water stress
• Key parameters of the photosynthesis model are affected by drought: the well-watered value are adjusted by using the Soil Wetness Index (SWI)• 2 possible strategies: drought-avoiding / drought-tolerant:
Mesophyll conductance gmMax leaf-to-air saturation deficit Dmax
Mesophyll conductance gmMax Ci coupling factor f0
DROUGHT-TOLERANT DROUGHT-AVOIDING
Crops, Grasslands
Trees, Shrubs
f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 0 SWI = 0f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 1 (unstressed)SWI = 1 (unstressed)
SWI = θC
ln(g
m(m
m s
-1))
SWI = 0
ln(Dmax (g kg-1))
SWI = 1 (unstressed)
ln(Dmax (g kg-1))
SWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θC
DROUGHT-TOLERANT DROUGHT-AVOIDING
Crops, Grasslands
Trees, Shrubs
f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 0 SWI = 0f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 1 (unstressed)SWI = 1 (unstressed)
SWI = θC
ln(g
m(m
m s
-1))
SWI = 0
ln(Dmax (g kg-1))
SWI = 1 (unstressed)
ln(Dmax (g kg-1))
SWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θC
DROUGHT-TOLERANT DROUGHT-AVOIDING
Crops, Grasslands
Trees, Shrubs
f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 0 SWI = 0f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 1 (unstressed)SWI = 1 (unstressed)
f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 0 SWI = 0f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 1 (unstressed)
SWI = 0f0
ln(g
m(m
m s
-1))
SWI = θC
SWI = 1 (unstressed)SWI = 1 (unstressed)
SWI = θC
ln(g
m(m
m s
-1))
SWI = 0
ln(Dmax (g kg-1))
SWI = 1 (unstressed)
ln(Dmax (g kg-1))
SWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θC
SWI = θC
ln(g
m(m
m s
-1))
SWI = 0
ln(Dmax (g kg-1))
SWI = 1 (unstressed)
ln(Dmax (g kg-1))
SWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θC ln(g
m(m
m s
-1))
SWI = 0
ln(Dmax (g kg-1))
SWI = 1 (unstressed)
ln(Dmax (g kg-1))
SWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θC
ln(Dmax (g kg-1))
SWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θCSWI = 0
ln(g
m(m
m s
-1)) SWI = 1 (unstressed)
SWI = θC
Calvet 2000, Calvet et al. 2004
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Respiration
• Ecosystem respiration is calculated by using a simple Q10 function depending on soil temperature this is enough to calculate a net CO2flux but NPP cannot be simulated
• Autotrophic respiration is calculated for the above-ground biomass only• Heterotrophic respiration is not explicitly calculated in the present version
Gifford 2003
ACTIVE BIOMASS
ABOVE-GROUND BIOMASS
Net assimilation of C
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Allocation
• The active biomass (= leaves) is a reservoir fed by the net CO2 uptake by leaves (i.e. An = Photosynthesis – Leaf respiration). It looses carbon following an exponential law whose e-folding time depends on the daily maximum An (parameter = max leaf span time).
• The above-ground biomass (non-woody) is derived from the active biomass:
Growing period: a logarithmic nitrogen dilution equation is used
Senescence: respiration losses and exponential decline
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Phenology
• LAI is linearly related to the active biomass (parameters = leaf nitrogen concentration and 2 plasticity parameters)• A minimum value of LAI is prescribed (e.g. 0.3 for annual vegetation), permitting a self restart of the vegetation when photosynthesis becomes active• Possibility to cut the vegetation or to maintain LAI at its minimum value, for agricultural applications
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Phenology
Merits of this methodology
• Simple• Leaf onset and offset dates don‘t have to be prescribed (permitting to simulate the interannual variability and climate change effects)• No use of empirical degree-day sums (all the factors are accounted for, not only temperature)
Other models using this approach
AVIM (Ji 1995, Dan et al. 2005)STEP (Mougin et al. 1995)
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Parameters at a global scale for the ECOCLIMAP vegetation types
0.3
1
1
0.3
0.3
0.3
0.3
LAImin(m2m-2)
230
365
365
150
150
150
150
τm(d)
0.15
0.15
0
0.15
0.25
0.15
0.25
gc(mm s-1)
2
2.5
2.8
1.3
1.3
1.9
1.3
NL (%)
2.53
2.53
-0.24
-4.33
6.73
-4.33
9.84
f(m2kg-1)
4.83
4.83
4.85
7.68
5.56
7.68
3.79
e(m2kg-1
%-1)
0.3
0.3
0.3
0.3
0.3
0.3
0.3
θc
3
2
2
6
1
9
1
gm(mm s-1)
Deciduous forests
Evergreen forests
Coniferous forests
C4 grasslands
C3 grasslands
C4 crops
C3 Crops
Vegetation type
Cuticular conductance
Mesophyll conductance
Critical SWI
Leaf N
N Plasticity parameters
Max leafspan time
Photosynthesis Allocation/Phenology
Gibelin et al. 2005
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ISBA-A-gs / C-TESSEL
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Example of Carbon flux simulations by ISBA-A-gs for Southwestern France (Toulouse)
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
ORCHIDEE
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
• Litter (above/below ground, structural/metabolic, natural/agricultural)• 3 soil organic matter pools (active, slow, passive)
Carbon storage
• Fire occurrence described in LPJFires
• Grass/tree competition and competition between tree species described in LPJ
Competition
• Degree-day model for leaf onset, accounting for soil moisture, tuned at a global scale by using satellite data• Senescence: soil moisture and temperature are accounted for
Phenology
• Allocation to leaves/stems/roots function of resources: water, light, nutrients (Tilman 1998)• 8 pools of living biomass
Allocation
• CENTURY-like modelHeterotrophic respiration
• Maintenance respiration: linear response to temperature (Ruimy et al.), and possible adaptation to climate change• Growth respiration: a fixed part of net assimilation
Autotrophic respiration
• Biochemical approach (Farquhar, Ball & Berry)Photosynthesis
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Representation of land surface patchiness
Modelling of the carbon cycle in the geoland project
S. Lafont
geoland
06.09.2005
Usefulness of tiling
Herbaceous classes of ECOCLIMAP:Mainly 4 ‘metaclasses’
type 1 type 2
Usefulness of tiling
Herbaceous classes of ECOCLIMAP:Mainly 4 ‘metaclasses’
type 1 type 2
½ × ½ °
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Representation of land surface patchiness
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
S. Lafont
Usefulness of tiling
Herbaceous classes of ECOCLIMAP:Fraction of type 2 can be high
8 tiles:
•bare soil (and rock/snow)•Deciduous forests•Coniferous forests•Evergreen forests•grass C3•grass C4•crops C3•crops C4
Usefulness of tiling
Herbaceous classes of ECOCLIMAP:Fraction of type 2 can be high
8 tiles:
•bare soil (and rock/snow)•Deciduous forests•Coniferous forests•Evergreen forests•grass C3•grass C4•crops C3•crops C4
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: LAI
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Yearly maximum of LAI
ISBA-A-gs
MODIS
ISLSCP-2
ECOCLIMAP
Gibelin et al. 2005
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: LAI
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Zonal mean of the maximum of LAIsimulated by ISBA-A-gs (mean 1986-1995), ISLSCP-II data set (mean 1986-1995), MODIS data set (mean 2001-2004), ECOCLIMAP data set (climatology).
Gibelin et al. 2005
MODIS
ISLSCP-2Model
ECOCLIMAP
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: LAI
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Correlation of the monthly LAI anomaly (difference between monthly LAI and the mean annual cycle) between ISBA-A-gs and the ISLSCP-II data (1986-1995).
Gibelin et al. 2005
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: LAI
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Monthly time series of LAI from ISBA-A-gs and ISLSCP-II over Southern Africa [-35°N:-15°N, 10°E:40°E]
Gibelin et al. 2005
ISBA-A-gs
ISLSCP-2
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: LAI
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Sahel Southern Africa
Relative anomaly of LAI (%) versus precipitation anomaly (mm d-1) (blue boxes: ISLSCP2 ; red dots: ISBA-A-gs ; green bars: precipitation)
Gibelin et al. 2005
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: LAI
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Start of the growing season (mean 1986-1995) simulated by ISBA-A-gs and observed in ISLSCP-II
ISBA-A-gs ISLSCP-2
Gibelin et al. 2005
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: FaPAR
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
N. Viovy
2003 FaPAR anomaly:ORCHIDEE (2003-1972/2002)MODIS (2003-2000/2002) – Reinstein
ORCHIDEE MODIS
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: water flux comparison with operational models
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
A.-L. Gibelin
Comparison of the evapo-transpiration flux (JJA) of ISBA and ISBA-A-gs
ISBA standard ISBA standard − ISBA-A-gs
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: ground-based flux measurements
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
N. Viovy
Validation of the ORCHIDEE fluxes by using more than 30 FLUXNET sites: Average diurnal cycle
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: ground-based flux measurements
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
N. Viovy
Validation of the ORCHIDEE fluxes by using more than 30 FLUXNET sites: Average seasonal cycle
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: crop production
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
N. Viovy
1900-2000 crop production simulated by the STICS module of ORCHIDEE over Europe: the management effect
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: crop production
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Wheat yield (t ha-1) estimated by ISBA-A-gs for the area of Toulouse, by assuming a Harvest Index of 0.5
Spring wheat
Winter wheat
5.3 6.2 4.2 4.6
6.2 6.2 4.8 5.8
- 5.9 4.6 5.7 Observation for Midi-Pyrénées
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
VALIDATION: crop production
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Maize yield (t ha-1) estimated by ISBA-A-gs for the area of Toulouse, by assuming a Harvest Index of 0.5
Rainfed maize
Irrigated maize
6.1 8.1 4.4 4.7
8.9 8.4 8.5 8.3
- 8.6 6.0 8.1 Observation for Midi-Pyrénées
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Data Assimilation
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
x is the control variables vectory is the observation vectorH is the observation operator
LAI
t
Bm
t
The analysis is obtained by the minimization of the cost function J(x)
B is the background error covariance matrix
R is the observation error covariance matrix
= ½ (x – xb) T B-1 (x – xb) + ½(y – H(x))T R-1 (y – H(x))
J(x) = J b(x) + J o(x)Formalism: Minimization of a cost function
Observations
Analysis
Litteral solution for linear model :xa = xb + K(y-Hxb)
with K = BHT(HBHT+R)-1
x is the control variables vectory is the observation vectorH is the observation operator
LAI
t
Bm
t
The analysis is obtained by the minimization of the cost function J(x)
B is the background error covariance matrix
R is the observation error covariance matrix
= ½ (x – xb) T B-1 (x – xb) + ½(y – H(x))T R-1 (y – H(x))
J(x) = J b(x) + J o(x)Formalism: Minimization of a cost function
Observations
Analysis
Litteral solution for linear model :xa = xb + K(y-Hxb)
with K = BHT(HBHT+R)-1
The variational approach
L. Jarlan
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Data Assimilation
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
A simplified algorithm (adapted from Balsamo and Bouyssel)
L. Jarlan
Binit B’init=Binit + δBinit
⎟⎟⎟⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜⎜⎜⎜
⎝
⎛
=T
LAIδΒ init
δ (1)
...H
From a perturbation of the initial total biomass δ Binit applied on each model land grid-point.
δLAI (i) = LAIG (i) - LAIG’ (i)Guess G
Guess G’
LAI
tt=0 1 2 … p
δBinit
LAIδΒ init
δ (p)
Numerical linearization of the observation operator H
Binit B’init=Binit + δBinit
⎟⎟⎟⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜⎜⎜⎜
⎝
⎛
=T
LAIδΒ init
δ (1)
...H
From a perturbation of the initial total biomass δ Binit applied on each model land grid-point.
δLAI (i) = LAIG (i) - LAIG’ (i)Guess G
Guess G’
LAI
t
LAI
tt=0 1 2 … pt=0 1 2 … p
δBinit
LAIδΒ init
δ (p)
Numerical linearization of the observation operator H
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Data Assimilation
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
A simplified algorithm (adapted from Balsamo and Bouyssel)
L. Jarlan
Two main hypotheses have to be validated
••TLTL (linearity)
••2D2D (horizontal decoupling)
H(Binit)
H(Binit)for
δBinit≈ σBBinit
Minimization of the cost function with a look up table …… + comparison to a sequential stochastic approach
(Ensemble Kalman Filter, not shown)
Verified at our spatial scale ?
Two main hypotheses have to be validated
••TLTL (linearity)
••2D2D (horizontal decoupling)
H(Binit)
H(Binit)for
δBinit≈ σBBinit
for δBinit≈ σB
Binit
Minimization of the cost function with a look up table …… + comparison to a sequential stochastic approach
(Ensemble Kalman Filter, not shown)
Verified at our spatial scale ?
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Data Assimilation
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Application to the SMOSREX fallow
L. Jarlan
Analysis of Biomass thanksto in situ LAI observations(10 days analysis period)
Perfect LAI correction
Overall good Biomass analysis (particularly in 2002)
Low impact on w2 (different LAI differentroot water extraction andtranspiration rates)
Analysis of Biomass thanksto in situ LAI observations(10 days analysis period)
Perfect LAI correction
Overall good Biomass analysis (particularly in 2002)
Low impact on w2 (different LAI differentroot water extraction andtranspiration rates)
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Data Assimilation
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
Application to the SMOSREX fallow
L. Jarlan
Analysis of Biomass andw2 thanks to in situ LAI observations (10 daysanalysis period)
Perfect LAI correction
Overall good Biomassanalysis
High scattering of analysed w2 …
… but w2 better in agreement with observations during high water stress period
Analysis of Biomass andw2 thanks to in situ LAI observations (10 daysanalysis period)
Perfect LAI correction
Overall good Biomassanalysis
High scattering of analysed w2 …
… but w2 better in agreement with observations during high water stress period
Observatory Natural Carbon Fluxes Jean-Christophe Calvet
Météo-France
Prospects
Modelling of the carbon cycle in the geoland project
geoland
06.09.2005
• ISBA-A-gs / C-TESSEL (Météo-France / ECMWF)RootsWoodSoil carbonNPP
• Representation of land surface patchinessRegional applications (5-10 km) at Météo-France and LSCE
• VALIDATION:Test of C-TESSEL global simulations of LAITest of ISBA-A-gs and C-TESSEL using the FLUXNET data
• Data AssimilationISBA-A-gs: Use of a 2D assimilation system over South-Western France using
SPOT/VGT data (1999-2005)Global assimilation of LAI products in ORCHIDEE and C-TESSEL
Integrated GMES Project on Landcover and Vegetation
Co-funded by the European Commission within the GMES initiative in FP-6
geoland
Thank you for your attention!
www.gmes-geoland.info
Contact: geoland coordinators:
Medias-France
Infoterra GmbH
Jean-Christophe Calvet
+33 561079341