Aggregation effects of surface heterogeneity in land surface processes

Su, Zhongbo; Pelgrum, H.; Menenti, Massimo

doi:10.5194/hess-3-549-1999

Cited by 79 publications

(52 citation statements)

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“…Documented research has demonstrated that the spatial/temporal resolutions of climate, geographical and ecological factors may lead to noticeably different outputs (Su et al, 1999;Yang et al, 2001;Xu & Yan, 2005), and the scaling effects of surface heat fluxes increase with land surface heterogeneity (Sridhar et al, 2003), since spatial information may get lost with a coarse grid size in modelling (Schoorl et al, 2000). It has been reported that simulated runoff increased and actual evapotranspiration (ET) decreased, while grid size changed from coarse to fine (Famiglietti & Wood, 1994;Arola & Lettenmaier, 1996;Finnerty et al, 1997;Becker & Braun, 1999;Kuo et al, 1999;Cerdan et al, 2004;Hessel, 2005).…”

Section: Introductionmentioning

confidence: 99%

Grid-size effects on estimation of evapotranspiration and gross primary production over a large Loess Plateau basin, China

Liu

Chen

et al. 2009

Hydrological Sciences Journal

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A distributed eco-hydrological model based on soil vegetation atmosphere transfer processes is applied to estimate actual evapotranspiration (ET) and gross primary production (GPP) over the Wuding River basin, Loess Plateau, China, based on digital elevation model, vegetation and soil information between 2000 and 2003 over three grid sizes: 250 m, 1 km and 8 km. The spatial patterns of annual ET and GPP are related to precipitation variability and land-use/cover conditions. The grid size is shown to affect the spatial patterns of annual ET and GPP, the effect on GPP being more significant than that on ET. Geostatistical and regression analyses demonstrate that precipitation and vegetation influence the scaling effect of ET and GPP in a complex way. When precipitation is high, the scaling effect of ET is more dependent on precipitation. The scaling effect of ET and GPP from 1-km to 8-km grid size is much larger than that from 250-m to 1-km grid size, showing the 1-km grid size to be a feasible choice for simulation of their spatial patterns. Although the annual GPP is more sensitive to the grid size than annual ET, both daily ET and daily GPP averaged over the whole basin seem to be insensitive to the grid size, illustrating that the coarse grid size can be used to simulate spatially-averaged variables without losing much accuracy.Key words distributed eco-hydrological model; scaling effect; evapotranspiration; gross primary production Effets de la résolution du maillage spatial sur l'estimation de l'évapotranspiration et de la production primaire brute au sein d'un grand bassin versant du Plateau Loessique Résumé Un modèle éco-hydrologique distribué, basé sur les processus de transfert dans le continuum solplante-atmosphère, est appliqué pour estimer l'évapotranspiration réelle (ET) et la production primaire brute (PPB) au sein du bassin versant de la Rivière Wuding, dans le Plateau Loessique chinois. L'application s'appuie sur un modèle numérique de terrain et des informations relatives à la végétation et au sol de la période 2000-2003, pour trois résolutions de maillage: 250-m, 1-km et 8-km. Les organisations spatiales de l'ET et de la PPB annuelles sont corrélées avec la variabilité des précipitations et avec l'occupation du sol. La résolution du maillage se révèle avoir de l'influence sur l'organisation de l'ET et de la PPB annuelles, l'effet sur la PPB étant plus significatif que sur l'ET. Des analyses géostatistiques et par régression mettent en évidence que les précipitations et la végétation influencent l'effet d'échelle de l'ET et de la PPB d'une façon complexe. Lorsque les précipitations sont importantes, l'effet d'échelle de l'ET est plus dépendant des précipitations. L'effet d'échelle de l'ET et de la PPB entre les résolutions de maillage de 1 et de 8 km est plus fort qu'entre les résolutions de 250 m et de 1 km, ce qui montre que la résolution de 1 km est un choix possible pour la simulation de leurs organisations spatiales. Bien que la PPB annuelle soit plus sensible à la résolution de la ...

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Section: Introductionmentioning

confidence: 99%

Grid-size effects on estimation of evapotranspiration and gross primary production over a large Loess Plateau basin, China

Liu

Chen

et al. 2009

Hydrological Sciences Journal

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“…SEBS is often used as a remote sensing algorithm for estimating (daily) evapotranspiration. It consists of a set of algorithms for the determination of the land surface physical parameters and variables, such as albedo, emissivity, land surface temperature, and vegetation coverage, from spectral reflectance and radiance data (Su et al, 1999(Su et al, , 2001Su, 1996). It includes an extended model for the determination of the roughness height for heat transfer (Su et al, 2001) and a formulation for the estimation of the evaporative fraction on the basis of the energy balance at limiting cases.…”

Section: Sebsmentioning

confidence: 99%

Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models

Timmermans

Tol

et al. 2013

Hydrol. Earth Syst. Sci.

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Abstract. 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 soilvegetation-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.

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“…In the past decades, many algorithms using remote sensing information to estimate ET have been developed, and from simple and empirical approaches to complex and data consuming ones. These can be put into two groups broadly: (1) to estimate ET by set empirical relation between ET and parameters (vegetation index, temperature, albedo) that could be measured from meteorological satellites (Index, 1994;Boegh, 2002;McCabe et al, 2005); (2) to calculate the sensible heat flux first and then obtain the latent heat flux as the residual of the energy balance equation, SEBAL (Bastiaanssen et al, 1998), SEBS (Su et al, 1999;Su, 2002), NTDI (McVicar and Jupp, 1999). Most models require a complex and high-quality input data to obtain accurate results and each method has limitations (Bashir et al, 2008).…”

Section: R Liu Et Al: Meris and Aatsr Data Over The Chinese Loess Pmentioning

confidence: 99%

Actual daily evapotranspiration estimated from MERIS and AATSR data over the Chinese Loess Plateau

Liu

Wen

Wang

et al. 2010

Hydrol. Earth Syst. Sci.

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Abstract. The Chinese Loess Plateau is located in the north of China and has a significant impact on the climate and ecosystem evolvement over the East Asian continent. Estimates of evapotranspiration (ET) at a regional scale are in crucial need for climate studies, weather forecasts, hydrological surveys, ecological monitoring and water resource management. In this research, the ET of the Chinese Loess Plateau was estimated by using an energy balance approach and data collected during the LOess Plateau land-atmosphere interaction pilot EXperiments 2005 (LOPEX05). With the combined data of the Medium Resolution Imaging Spectrometer (MERIS), the Advanced Along-Track Scanning Radiometer (AATSR) and some other variables such as air temperature, crop height and wind speed, the instantaneous net radiation, sensible heat flux and soil heat flux were calculated; the instantaneous latent heat flux was derived as the residual term of energy balance, and then converted to daily ET value by sunshine duration. The calculated daily ET from the model showed a good match with the measurements of the eddy covariance systems deployed in LOPEX05. The minimum relative error of this approach is 9.0%, the cause of the bias was also explored and discussed.

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Aggregation effects of surface heterogeneity in land surface processes

Cited by 79 publications

References 0 publications

Grid-size effects on estimation of evapotranspiration and gross primary production over a large Loess Plateau basin, China

Grid-size effects on estimation of evapotranspiration and gross primary production over a large Loess Plateau basin, China

Quantifying the uncertainty in estimates of surface–atmosphere fluxes through joint evaluation of the SEBS and SCOPE models

Actual daily evapotranspiration estimated from MERIS and AATSR data over the Chinese Loess Plateau

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