Evaluation of the Surface Energy Balance System (SEBS) applied to ASTER imagery with flux-measurements at the SPARC 2004 site (Barrax, Spain)

Abstract

Abstract. Accurate quantification of the amount and spatial variation of evapotranspiration is important in a wide range of disciplines. Remote sensing based surface energy balance models have been developed to estimate turbulent surface energy fluxes at different scales. The objective of this study is to evaluate the Surface Energy Balance System (SEBS) model on a landscape scale, using tower-based flux measurements at different land cover units during an overpass of the ASTER sensor over the SPARC 2004 experimental site in Barrax (Spain). A sensitivity analysis has been performed in order to investigate to which variable the sensible heat flux is most sensitive. Taking into account their estimation errors, the aerodynamic parameters (h c , z 0M and d 0 ) can cause large deviations in the modelling of sensible heat flux. The effect of replacement of empirical derivation of these aerodynamic parameters in the model by field estimates or literature values is investigated by testing two scenarios: the Empirical Scenario in which empirical equations are used to derive aerodynamic parameters and the Field Scenario in which values from field measurements or literature are used to replace the empirical calculations of the Empirical Scenario. In the case of a homogeneous land cover in the footprints of the measurements, the Field Scenario only resulted in a small improvement, compared to the Empirical Scenario. The Field Scenario can even worsen the result in the case of heterogeneous footprints, by creating sharp borders related to the land cover map. In both scenarios modelled fluxes correspond Correspondence to: J. van der Kwast (hans.vanderkwast@vito.be) better with flux measurements over uniform land cover compared to cases where different land covers are mixed in the measurement footprint. Furthermore SEBS underestimates sensible heat flux especially over dry and sparsely vegetated areas, which is common in single-source models.

Evapotranspiration Mapping in a Heterogeneous Landscape Using Remote Sensing and Global Weather Datasets: Application to the Mara Basin, East Africa

“…T s is one of the key drivers in the physics of land-surface processes, such as SEB. Previous studies highlighted the influence of the quality of T s on the accuracy of the ET estimates from SEB [23,24]. Therefore, we used only cloud-free T s images with quality flag 0 and/or an accuracy level within ±1 K. Given the tropical location of the study area, there are gaps in the T s images, particularly in the mountainous region, due to cloud contamination.…”

Reconnoitering the effect of shallow groundwater on land surface temperature and surface energy balance using MODIS and SEBS

“…It has been extensively applied and validated with a variety of methods in different regions and climates (Su, 2002;Jia et al, 2003Jia et al, , 2009Su et al, 2005;McCabe and Wood, 2006;McCabe et al, 2008;Badola, 2009;van der Kwast et al, 2009;Gibson et al, 2011).…”

“…USA, Mexico, China, India, Pakistan, Australia, etc. (Dregne et al, 1996;Rahman, 2008;Umali, 1993;Middleton and Thomas, 1997;Wichelns, 1999;World Bank, 1992;Xiong et al, 1996). The presence of a shallow water table is common in such areas due to high recharge rates, low drainage rates or small topographic slopes (Northey et al, 2006;Wichelns, 1999).…”

Review: Estimating evapotranspiration using remote sensing and the Surface Energy Balance System – A South African perspective

“…Additional inaccuracies have been ascribed to more than one landcover being present in one pixel (Van der Kwast et al, 2009) and landscape heterogeneity (Rwasoka et al, 2011). Furthermore, several authors have highlighted the parameters to which the SEBS model is most sensitive.…”