 |
| Titel |
Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models |
| VerfasserIn |
J. Timmermans, Z. Su, C. Tol, A. Verhoef, W. Verhoef |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 4 ; Nr. 17, no. 4 (2013-04-22), S.1561-1573 |
| Datensatznummer |
250018857
|
| Publikation (Nr.) |
 copernicus.org/hess-17-1561-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
Accurate estimation of global evapotranspiration is considered to be of great
importance due to its key role in the terrestrial and atmospheric water
budget. Global estimation of evapotranspiration on the basis of
observational data can only be achieved by using remote sensing. Several
algorithms have been developed that are capable of estimating the daily
evapotranspiration from remote sensing data. Evaluation of remote sensing
algorithms in general is problematic because of differences in spatial and
temporal resolutions between remote sensing observations and field
measurements. This problem can be solved in part by using soil-vegetation-atmosphere transfer (SVAT) models, because on the one hand these models
provide evapotranspiration estimations also under cloudy conditions and on
the other hand can scale between different temporal resolutions.
In this paper, the Soil Canopy Observation, Photochemistry and Energy fluxes
(SCOPE) model is used for the evaluation of the Surface Energy Balance
System (SEBS) model. The calibrated SCOPE model was employed to simulate
remote sensing observations and to act as a validation tool. The advantages
of the SCOPE model in this validation are (a) the temporal continuity of the
data, and (b) the possibility of comparing different components of the energy
balance. The SCOPE model was run using data from a whole growth season of a
maize crop.
It is shown that the original SEBS algorithm produces large uncertainties in
the turbulent flux estimations caused by parameterizations of the ground
heat flux and sensible heat flux. In the original SEBS formulation the
fractional vegetation cover is used to calculate the ground heat flux. As
this variable saturates very fast for increasing leaf area index (LAI), the ground heat flux
is underestimated. It is shown that a parameterization based on LAI reduces
the estimation error over the season from RMSE = 25 W m−2 to
RMSE = 18 W m−2. In the original SEBS formulation the roughness
height for heat is only valid for short vegetation. An improved
parameterization was implemented in the SEBS algorithm for tall vegetation.
This improved the correlation between the latent heat flux predicted by the
SEBS and the SCOPE algorithm from −0.05 to 0.69, and led to a decrease in
difference from 123 to 94 W m−2 for the latent heat
flux, with SEBS latent heat being consistently lower than the SCOPE
reference. Lastly the diurnal stability of the evaporative fraction was
investigated. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|