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Remote sensing of transpiration and heat fluxes using multi-angle observations

Remote sensing of transpiration and heat fluxes using multi-angle observations
Remote sensing of transpiration and heat fluxes using multi-angle observations
Surface energy balance is a major determinant of land surface temperature and the Earth's climate. To date, there is no approach that can produce effective, physically consistent, global and multi-decadal energy–water flux data over land. Net radiation (Rn) can be quantified regionally using satellite retrievals of surface reflectance and thermal emittance with errors < 10%. However, consistent, useful retrieval of latent heat flux (?E) from remote sensing is not yet possible. In theory, ?E could be inferred as a residual of Rn, ground heat (G) and sensible heat (H) fluxes (Rn–H–G). However, large uncertainties in remote sensing of both H and G result in low accuracies for ?E. Where vegetation is the dominant surface cover, ?E is largely driven by transpiration of intercellular water through leaf stomata during the photosynthetic uptake of carbon. In these areas, satellite retrievals of photosynthesis (GPP) could be used to quantify transpiration rates through stomatal conductance. Here, we demonstrate how remote sensing of GPP could be applied to obtain ?E from passive optical measurements of vegetation leaf reflectance related to the photosynthetic rate independent of knowledge of H, Rn and G. We validate the algorithm using five structurally and physiologically diverse eddy flux sites in western and central Canada. Results show that transpiration and H were accurately predicted from optical data and highly significant relationships were found between the energy budget obtained from eddy flux measurements and remote sensing (0.64 ? r2 ? 0.85). We conclude that spaceborne estimates of GPP could significantly improve not only estimates of the carbon balance but also the energy balance over land.
ball-berry relationship, gpp, stomatal conductance, transpiration, multi-angle remote sensing amspec
0034-4257
31-42
Hilker, Thomas
c7fb75b8-320d-49df-84ba-96c9ee523d40
Hall, Forrest G.
19da6ee8-b54b-4eee-b5b6-e8e3a92f6bcf
Coops, Nicholas C.
5511e778-fec2-4f54-8708-de65ba5a0992
Collatz, James G.
b48020ad-815d-4e18-a3a8-4a747ed74843
Black, T. Andrew
f6187e30-d043-4094-b5ef-372c60de403b
Tucker, Compton J.
3aaff73d-aa1f-49c0-9d16-7099c218b274
Sellers, Piers J.
c9d7b8a6-3ed9-4e9f-9318-cc287e746315
Grant, Nicholas
cb68df2e-c0eb-4ce7-968e-07d2713bacd9
Hilker, Thomas
c7fb75b8-320d-49df-84ba-96c9ee523d40
Hall, Forrest G.
19da6ee8-b54b-4eee-b5b6-e8e3a92f6bcf
Coops, Nicholas C.
5511e778-fec2-4f54-8708-de65ba5a0992
Collatz, James G.
b48020ad-815d-4e18-a3a8-4a747ed74843
Black, T. Andrew
f6187e30-d043-4094-b5ef-372c60de403b
Tucker, Compton J.
3aaff73d-aa1f-49c0-9d16-7099c218b274
Sellers, Piers J.
c9d7b8a6-3ed9-4e9f-9318-cc287e746315
Grant, Nicholas
cb68df2e-c0eb-4ce7-968e-07d2713bacd9

Hilker, Thomas, Hall, Forrest G., Coops, Nicholas C., Collatz, James G., Black, T. Andrew, Tucker, Compton J., Sellers, Piers J. and Grant, Nicholas (2013) Remote sensing of transpiration and heat fluxes using multi-angle observations. Remote Sensing of Environment, 137, 31-42. (doi:10.1016/j.rse.2013.05.023).

Record type: Article

Abstract

Surface energy balance is a major determinant of land surface temperature and the Earth's climate. To date, there is no approach that can produce effective, physically consistent, global and multi-decadal energy–water flux data over land. Net radiation (Rn) can be quantified regionally using satellite retrievals of surface reflectance and thermal emittance with errors < 10%. However, consistent, useful retrieval of latent heat flux (?E) from remote sensing is not yet possible. In theory, ?E could be inferred as a residual of Rn, ground heat (G) and sensible heat (H) fluxes (Rn–H–G). However, large uncertainties in remote sensing of both H and G result in low accuracies for ?E. Where vegetation is the dominant surface cover, ?E is largely driven by transpiration of intercellular water through leaf stomata during the photosynthetic uptake of carbon. In these areas, satellite retrievals of photosynthesis (GPP) could be used to quantify transpiration rates through stomatal conductance. Here, we demonstrate how remote sensing of GPP could be applied to obtain ?E from passive optical measurements of vegetation leaf reflectance related to the photosynthetic rate independent of knowledge of H, Rn and G. We validate the algorithm using five structurally and physiologically diverse eddy flux sites in western and central Canada. Results show that transpiration and H were accurately predicted from optical data and highly significant relationships were found between the energy budget obtained from eddy flux measurements and remote sensing (0.64 ? r2 ? 0.85). We conclude that spaceborne estimates of GPP could significantly improve not only estimates of the carbon balance but also the energy balance over land.

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More information

Accepted/In Press date: 25 May 2013
e-pub ahead of print date: 28 June 2013
Published date: October 2013
Keywords: ball-berry relationship, gpp, stomatal conductance, transpiration, multi-angle remote sensing amspec
Organisations: Earth Surface Dynamics

Identifiers

Local EPrints ID: 384695
URI: http://eprints.soton.ac.uk/id/eprint/384695
ISSN: 0034-4257
PURE UUID: 9adde995-2940-4954-9188-ec8ea08fca50

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Date deposited: 15 Apr 2016 15:44
Last modified: 14 Mar 2024 22:02

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Contributors

Author: Thomas Hilker
Author: Forrest G. Hall
Author: Nicholas C. Coops
Author: James G. Collatz
Author: T. Andrew Black
Author: Compton J. Tucker
Author: Piers J. Sellers
Author: Nicholas Grant

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