Quantification of land–atmosphere exchanges of water, energy and carbon dioxide in space and time over the heterogeneous Barrax site

Self Cite

101

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.

Section: Data Descriptionmentioning

confidence: 99%

“…In this study the turbulent sensible heat fluxes are modelled with SEBS, using ASTER in combination with field measurements collected during the SPARC 2004 field campaign of July 2004 in Barrax, Spain (Su et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

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

Kwast

Timmermans

Gieske

et al. 2009

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101

“…Sobrino et al, 2008;Su et al, 2008;Timmermans, 2008b, c), the knowledge of bio-geophysical parameter retrieval from multi-parameter optical, thermal and microwave data and the ability of direct modeling of the underlying physical processes in forests and grassland remain challenging due to lack of appropriate observation data in humid climate. In EAGLE2006 an intensive filed campaign was conducted using different airborne instruments -an optical imaging sensor, an imaging microwave radiometer, and a flux airplane -for data acquisition and to collect extensive ground measurements simultaneously over one grassland site and two forest sites in addition to acquisition of multi-angle and multi-sensor satellite data.…”

Section: Campaign Overviewmentioning

confidence: 99%

EAGLE 2006 – Multi-purpose, multi-angle and multi-sensor in-situ and airborne campaigns over grassland and forest

Su¹,

Timmermans²,

Tol³

et al. 2009

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Abstract. EAGLE2006 -an intensive field campaign for the advances in land surface hydrometeorological processes -was carried out in the Netherlands from 8th to 18th June 2006, involving 16 institutions with in total 67 people from 16 different countries. In addition to the acquisition of multiangle and multi-sensor satellite data, several airborne instruments -an optical imaging sensor, an imaging microwave radiometer, and a flux airplane -were deployed and extensive Correspondence to: Z. Su (b su@itc.nl) ground measurements were conducted over one grassland site at Cabauw and two forest sites at Loobos and Speulderbos in the central part of the Netherlands. The generated data set is both unique and urgently needed for the development and validation of models and inversion algorithms for quantitative land surface parameter estimation and land surface hydrometeorological process studies. EAGLE2006 was led by the Department of Water Resources of the International Institute for Geo-Information Science and Earth Observation (ITC) and originated from the combination of a number of initiatives supported by different funding agencies. The objectives of the EAGLE2006 campaign were closely Published by Copernicus Publications on behalf of the European Geosciences Union. 834 Z. Su et al.: EAGLE 2006 -Multi-purpose, multi-angle and multi-sensor in-situ and airborne campaigns related to the objectives of other European Space Agency (ESA) campaign activities (SPARC2004, SEN2FLEX2005 and especially AGRISAR2006). However, one important objective of the EAGLE2006 campaign is to build up a data base for the investigation and validation of the retrieval of bio-geophysical parameters, obtained at different radar frequencies (X-, C-and L-Band) and at hyperspectral optical and thermal bands acquired simultaneously over contrasting vegetated fields (forest and grassland). As such, all activities were related to algorithm development for future satellite missions such as the Sentinels and for validation of retrievals of land surface parameters with optical and thermal and microwave sensors onboard current and future satellite missions. This contribution describes the campaign objectives and provides an overview of the airborne and field campaign dataset. This dataset is available for scientific investigations and can be accessed on the ESA Principal Investigator Portal http://eopi.esa.int.

“…The closure of the energy balance with raw data shows a linear regression forced through the origin equal to y = 0.773 x with R 2 = 0.946 (SEN2FLEX Final Report, 2006;Su et al, 2008). Only daytime data are used for this comparison due to problems in turbulent fluxes retrieval during stable atmospheric conditions which are typical of night (Wilson et al, 2002).…”

Section: Comparison With Energy Fluxes From Eddy Covariance Stationmentioning

confidence: 99%

“…The used data set was collected during a field campaign from 10 to 15 July 2005 in the framework of the SEN2FLEX (SENtinel-2 and FLuorescence EXperiment) project funded by ESA (SEN2FLEX Final Report, 2006;Sobrino et al, 2008;Su et al, 2008). …”

Section: Introductionmentioning

confidence: 99%

Land surface temperature representativeness in a heterogeneous area through a distributed energy-water balance model and remote sensing data

Corbari

Sobrino

Mancini

et al. 2010

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Abstract. Land surface temperature is the link between soilvegetation-atmosphere fluxes and soil water content through the energy water balance. This paper analyses the representativeness of land surface temperature (LST) for a distributed hydrological water balance model (FEST-EWB) using LST from AHS (airborne hyperspectral scanner), with a spatial resolution between 2-4 m, LST from MODIS, with a spatial resolution of 1000 m, and thermal infrared radiometric ground measurements that are compared with the representative equilibrium temperature that closes the energy balance equation in the distributed hydrological model. Diurnal and nocturnal images are analyzed due to the non stable behaviour of the thermodynamic temperature and to the non linear effects induced by spatial heterogeneity.Spatial autocorrelation and scale of fluctuation of land surface temperature from FEST-EWB and AHS are analysed at different aggregation areas to better understand the scale of representativeness of land surface temperature in a hydrological process.The study site is the agricultural area of Barrax (Spain) that is a heterogeneous area with a patchwork of irrigated and non irrigated vegetated fields and bare soil. The used data set was collected during a field campaign from 10 to 15 July 2005 in the framework of the SEN2FLEX project.