Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Record number 412247
Title On the temporal upscaling of evapotranspiration from instantaneous remote sensing measurements to 8-day mean daily-sums
Author(s) Ryu, Y.; Baldocchi, D.D.; Black, T.A.; Moors, E.J.
Source Agricultural and Forest Meteorology 152 (2012). - ISSN 0168-1923 - p. 212 - 222.
DOI https://doi.org/10.1016/j.agrformet.2011.09.010
Department(s) CWC - Earth System Science and Climate Change
WIMEK
Publication type Refereed Article in a scientific journal
Publication year 2012
Keyword(s) carbon-dioxide exchange - net ecosystem productivity - co2 exchange - energy fluxes - water-vapor - heterogeneous landscape - temperate grassland - daily evaporation - surface fluxes - boundary-layer
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 10:00 hh and 14:00 hh 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.
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