Forrest G. Hall 1 Thomas Hilker 1 Compton J. Tucker 1 Nicholas C. Coops 2 T. Andrew Black 2
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Transcript of Forrest G. Hall 1 Thomas Hilker 1 Compton J. Tucker 1 Nicholas C. Coops 2 T. Andrew Black 2
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Forrest G. Hall1
Thomas Hilker1
Compton J. Tucker1
Nicholas C. Coops2
T. Andrew Black2
Caroline J. Nichol3
Piers J. Sellers1
1NASA Goddard Space Flight Center Greenbelt, MD, USA2University of British Columbia, Vancouver, BC Canada3University of Edinburgh, Edinburgh EH9 3JN, UK
Data assimilation of photosynthetic light-use efficiency using multi-angular
satellite data
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CARBON CYCLE
WATER CYCLE
ENERGY CYCLE
PAR
PHOTOSYNTHETIC RATEGross Primary Production
GPP = PAR x Fpar x e Net Primary ProductionNPP = GPP – Respiration
Evapotranspiration ET = Transpiration + Evaporation
CARBON, WATER & ENERGY CYCLE
T ~[e*- ea]gc+ga
gcga
R = GPP – NPP spectral eddy corr
gc = a + b GPP x (h/c)
Light Use Efficiencymol C/ mol photon
GPP RNightimeTemp based
NPP eddy corr
GPP = NPP - R
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0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 wavelength(µm)
1
0.8
0.6
0.4
0.2
0
pigmentsleaf structure and leaf area water absorption
refle
ctan
ce
Associated changes in reflectance
0.50 0.55 0.60
wavelength (m)
refle
ctan
ce
0.05
0.10
0.15
531570
531570
PRI
] = Δζ
531nm 570nm
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4Hilker et al., Remote Sensing of Environment (2010)
Multi-angle Remote Sensing of ε
AMSPEC
256 bands350-1200nm10nm bandwidth
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shaded sunlit shaded
ε= low
ε = high
Hall et al. Rem. Sens. Environ. (2008,2012)
Effects of Function on Canopy PRI l
ow
h
igh
Insensitive to ς
ε
PRI’
Δρ@531nm from down-regulation)
Unstressed canopy PRI
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shaded sunlit shaded
Hall et al. Rem. Sens. Environ. (2008,2012)
Orbital Canopy PRI’ and ε l
ow
h
igh
X
ε = high
ε= low
4 3 2 1
123 4
Ground Track
ε
<PRI
’>
ε =
ε op
t PRI’ = PRI’max
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Differences Among Test Sites
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Hilker et al., Journal of Geophysical Research (2011)
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Satellite-derived Photosynthesis
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Hilker et al., Journal of Geophysical Research (2011)
(PR
I’)
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Remote sensing of ε across sites1st derivative of PRI (wrt αs) vs. ε
Tower-Based
AM
SP
EC
Spe
ctro
met
er B
ased
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Temporal Scaling of PhotosynthesisData assimilation
Hilker et al., Remote Sensing of Environment (submitted)
εopt (t1)εopt (t2) εopt (t3)
εopt (tn)
Spectrally Derived Instantaneous
Diurnal Spatially Explicit Time Series
εopt
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Two years of Ɛopt from CHRIS-PROBA
time06/0
4/06
07/0
6/06
08/2
6/06
10/0
1/06
08/0
2/07
07/0
6/07
10/2
7/06
εopt
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Resp
onse
func
tions
Hall et al. RSE (2012)
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Model comparison: GPPMODIS GPP model:Tower fPAR, PAR, MODIS ɛ
Data assimilation model:Tower fPAR, PAR, assimilated ɛ
Hilker et al. RSE (2012)
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Comparing Fluxes: EC, MODIS, Data assimilation model
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Assimilation
Hilker et al. RSE (2012)
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Respiration
GPP=NPP-R
We can determine R independently of TSoil
NEP GEP
Hilker et al. Ag and For Met (2012)
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Diurnal variability of R
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Hilker et al. Ag and For Met (2012)
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Energy balance
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H λE
Hilker et al. GCB (2012)
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Energy Balance: λE
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Hilker et al. GCB (2012)
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Energy Balance(spectral) λE+H = (tower)RN - G ?
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Hilker et al. GCB (2012)
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Recent relevant publications:1. Hall, F.G., et al., N.C., 2012. Data assimilation of photosynthetic light-use efficiency
using multi-angular satellite data: I. Model formulation. Rem. Sens. Environ., 121: 301–308.
2. Hilker, T. et al., 2012a. Data assimilation of photosynthetic light-use efficiency using multi-angular satellite data: II Model implementation and validation. Rem. Sens. Environ., 121: 287–300
3. Hilker, T. et al., 2012b. A new technique for estimating daytime respiration of forest ecosystems. Agr. For. Met.
4. Hilker, T. et al., 2012c. On the Remote Sensing of Heat Fluxes and Surface Energy Balance. Global Change Biology.
5. Hilker, T. et al., 2011. Inferring terrestrial photosynthetic light use efficiency of temperate ecosystems from space. JGR-Biogeosc., 116.
6. Hall, F.G. et al., 2011. PHOTOSYNSAT, photosynthesis from space: Theoretical foundations of a satellite concept and validation from tower and spaceborne data. Rem. Sens. Environ., 115(8): 1918-1925.
7. Hilker, T. et al., 2010. Remote sensing of photosynthetic light-use efficiency across two forested biomes: Spatial scaling. Rem. Sens. Environ., 114: 2863–2874.
8. Hall, F.G. et al., 2008. Multi-angle remote sensing of forest light use efficiency by observing PRI variation with canopy shadow fraction. Rem. Sens. Environ., 112(7): 3201-3211.
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Conclusions1. PRI’ quantifies light use efficiency (LUE) independent of
ecosystem variations in canopy structure and unstressed reflectance.
2. Near instantaneous multi-angle data are required to simultaneously quantify PRI and shadow fraction.
3. For the first time we have an eddy-correlation independent, spectral method to quantify GPP from towers and space.
4. Used in a data assimilation mode with GPP model, our satellite GPP algorithm can provide high spatial resolution, diurnal estimates of GPP.
• The ability to infer light use efficiency at regional scales allows us also to infer respiration independently of Tsoil and
• To remotely sense the key components of the surface energy balance.
5. A network of AMSPEC sites (@≈30k ea) could help rapidly refine process understanding and modeling in other ecosystems.
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Recommendations
• A wide-swath (~700km) satellite (along track multi-angle viewing) with PRI bands, chlorophyll absorption and NIR bands (for Fpar) could provide important advancements in the quantification and understanding of the global carbon, water and energy cycle.
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Spaceborne photosynthesis
Figure: NASA Goddard Space Flight Center 23