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| Titel |
How representative are instantaneous evaporative fraction measurements of daytime fluxes? |
| VerfasserIn |
J. Peng, M. Borsche, Y. Liu, A. Loew |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 10 ; Nr. 17, no. 10 (2013-10-15), S.3913-3919 |
| Datensatznummer |
250085954
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| Publikation (Nr.) |
 copernicus.org/hess-17-3913-2013.pdf |
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| Zusammenfassung |
| Sun-synchronous optical and thermal remote sensing is a promising technique
to provide instantaneous ET (evapotranspiration) estimates during satellite
overpass. The common approach to extrapolate the instantaneous estimates to
values for daily or longer periods relies on the assumption that the EF
(evaporative fraction, defined as the ratio of latent heat flux to surface
available energy) remains nearly constant during daytime. However, there is
still no consensus on the validity of the self-preservation of the EF. We
use FLUXNET (a global network of eddy covariance stations) measurements to
examine this self-preservation, and the conditions under which it can hold.
It is found that the instantaneous EF could represent daytime EF under clear
sky conditions, especially between 11:00 and 14:00 LT (local time) for
all stations. However, the results show that the EF is more variable during
cloudy sky conditions, so that an increase in cloud cover results in an
increase in the variability of the EF during daytime. |
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