On the temporal upscaling of evapotranspiration from instantaneous remote sensing measurements to 8-day mean daily-sums

Youngryel Ryu; Dennis D. Baldocchi; T. Andrew Black; Matteo Detto; Beverly E. Law; Ray Leuning; Akira Miyata; Markus Reichstein; Rodrigo Vargas; Christof Ammann; Jason Beringer; Lawrence B. Flanagan; Lianhong Gu; Lindsay B. Hutley; Joon Kim; Harry McCaughey; Eddy J. Moors; Serge Rambal; Timo Vesala

doi:10.1016/j.agrformet.2011.09.010

On the temporal upscaling of evapotranspiration from instantaneous remote sensing measurements to 8-day mean daily-sums

Youngryel Ryu, Dennis D. Baldocchi, T. Andrew Black, Matteo Detto, Beverly E. Law, Ray Leuning, Akira Miyata, Markus Reichstein, Rodrigo Vargas, Christof Ammann, Jason Beringer, Lawrence B. Flanagan, Lianhong Gu, Lindsay B. Hutley, Joon Kim, Harry McCaughey, Eddy J. Moors, Serge Rambal, Timo Vesala

Ecosystem Processes

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119 Scopus citations

Abstract

The regular monitoring of evapotranspiration from satellites has been limited because of discontinuous temporal coverage, resulting in snapshots at a particular point in space and time. We developed a temporal upscaling scheme using satellite-derived instantaneous estimates of evapotranspiration to produce a daily-sum evapotranspiration averaged over an 8-day interval. We tested this scheme against measured evapotranspiration data from 34 eddy covariance flux towers covering seven plant functional types from boreal to tropical climatic zones. We found that the ratio of a half-hourly-sum of potential solar radiation (extraterrestrial solar irradiance on a plane parallel to the Earth's surface) between 10:00hh and 14:00hh to a daily-sum of potential solar radiation provides a robust scaling factor to convert a half-hourly measured evapotranspiration to an estimate of a daily-sum; the estimated and measured daily sum evapotranspiration showed strong linear relation (r²=0.92) and small bias (-2.7%). By comparison, assuming a constant evaporative fraction (the ratio of evapotranspiration to available energy) during the daytime, although commonly used for temporal upscaling, caused 13% underestimation of evapotranspiration on an annual scale. The proposed temporal upscaling scheme requires only latitude, longitude and time as input. Thus it will be useful for developing continuous evapotranspiration estimates in space and time, which will improve continuous monitoring of hydrological cycle from local to global scales.

Original language	English
Pages (from-to)	212-222
Number of pages	11
Journal	Agricultural and Forest Meteorology
Volume	152
Issue number	1
DOIs	https://doi.org/10.1016/j.agrformet.2011.09.010
State	Published - Jan 15 2012

Funding

This work used eddy covariance data acquired by the FLUXNET community and in particular by the following networks: AmeriFlux (U.S. Department of Energy, Biological and Environmental Research, Terrestrial Carbon Program (DE-FG02-04ER63917 and DE-FG02-04ER63911)), AfriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, CarboItaly, CarboMont, ChinaFlux, Fluxnet-Canada (supported by CFCAS, NSERC, BIOCAP, Environment Canada, and NRCan), GreenGrass, KoFlux (supported by Sustainable Water Resources Center of 21C Frontier Research Program Code: 1-8-3 Korea), LBA, NECC, OzFlux, TCOS-Siberia, USCCC. We acknowledge the financial support to the eddy covariance data harmonization provided by CarboEuropeIP , FAO-GTOS-TCO , iLEAPS , Max Planck Institute for Biogeochemistry , National Science Foundation , University of Tuscia , Universite Laval and Environment Canada and US Department of Energy and the database development and technical support from Berkeley Water Center, Lawrence Berkeley National Laboratory, Microsoft Research eScience, Oak Ridge National Laboratory, University of California – Berkeley, University of Virginia. YR was supported by NASA Headquarters under the NASA Earth and Space Science Fellowship Program ( NNX08AU25H ) and the Berkeley Water Center/Microsoft eScience project . MODIS data processing was supported by Microsoft Azure cloud computing service. Drs. Andrew Richardson, John Norman, Oliver Sonnentag and Paul Stoy gave insightful comments. Data from the Tonzi and Vaira Ranches are supported by the Office of Science (BER), US Department of Energy, Grant DE-FG02-06ER64308. Data from Metolius sites are supported by the Office of Science (BER), US Department of Energy, Grant DE-FG02-06ER64318. Data collection at the Lethbridge grassland and western peatland sites in Canada were supported by the Natural Sciences and Engineering Research Council of Canada, the Canadian Foundation for Climate and Atmospheric Sciences, and BIOCAP Canada.

Funders	Funder number
AsiaFlux
BIOCAP
Berkeley Water Center/Microsoft
FAO-GTOS-TCO
LBA
Max Planck Institute for Biogeochemistry
Microsoft Azure cloud computing service
NECC
USCCC
Universite Laval and Environment Canada
National Science Foundation
U.S. Department of Energy
National Aeronautics and Space Administration	NNX08AU25H
Office of Science
Biological and Environmental Research	DE-FG02-04ER63911, DE-FG02-06ER64318, DE-FG02-04ER63917, DE-FG02-06ER64308
Oak Ridge National Laboratory
University of California Berkeley
University of Virginia
Università degli Studi della Tuscia
Natural Sciences and Engineering Research Council of Canada
Environment Canada
Natural Resources Canada
Canadian Foundation for Climate and Atmospheric Sciences

Keywords

Eddy covariance
Evapotranspiration
FLUXNET
MODIS
Temporal upscaling

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Ryu, Y., Baldocchi, D. D., Black, T. A., Detto, M., Law, B. E., Leuning, R., Miyata, A., Reichstein, M., Vargas, R., Ammann, C., Beringer, J., Flanagan, L. B., Gu, L., Hutley, L. B., Kim, J., McCaughey, H., Moors, E. J., Rambal, S., & Vesala, T. (2012). On the temporal upscaling of evapotranspiration from instantaneous remote sensing measurements to 8-day mean daily-sums. Agricultural and Forest Meteorology, 152(1), 212-222. https://doi.org/10.1016/j.agrformet.2011.09.010

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Ryu, Y, Baldocchi, DD, Black, TA, Detto, M, Law, BE, Leuning, R, Miyata, A, Reichstein, M, Vargas, R, Ammann, C, Beringer, J, Flanagan, LB, Gu, L, Hutley, LB, Kim, J, McCaughey, H, Moors, EJ, Rambal, S & Vesala, T 2012, 'On the temporal upscaling of evapotranspiration from instantaneous remote sensing measurements to 8-day mean daily-sums', Agricultural and Forest Meteorology, vol. 152, no. 1, pp. 212-222. https://doi.org/10.1016/j.agrformet.2011.09.010

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AU - Ryu, Youngryel

AU - Baldocchi, Dennis D.

AU - Black, T. Andrew

AU - Detto, Matteo

AU - Law, Beverly E.

AU - Leuning, Ray

AU - Miyata, Akira

AU - Reichstein, Markus

AU - Vargas, Rodrigo

AU - Ammann, Christof

AU - Beringer, Jason

AU - Flanagan, Lawrence B.

AU - Gu, Lianhong

AU - Hutley, Lindsay B.

AU - Kim, Joon

AU - McCaughey, Harry

AU - Moors, Eddy J.

AU - Rambal, Serge

AU - Vesala, Timo

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On the temporal upscaling of evapotranspiration from instantaneous remote sensing measurements to 8-day mean daily-sums

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