Dual versus single source models for estimating surface temperature of African savannah

Huntingford, Chris; Verhoef, Anne; Stewart, J.B.

doi:10.5194/hess-4-185-2000

Cited by 14 publications

(6 citation statements)

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“…It includes corrections for (1) the difference between thermal and mechanical roughness lengths, and (2) the difference between radiometric and aerodynamic temperatures. According to environmental conditions, thermal kB −1 varies from a vegetation type to another, and up to 100% in relative terms [113,219]. Parameterizations based on near surface wind speed and temperature gradients depend on sensible heat flux [220].…”

Section: Aerodynamic Temperaturementioning

confidence: 99%

Modeling and Inversion in Thermal Infrared Remote Sensing over Vegetated Land Surfaces

Jacob¹,

Schmugge

Olioso

et al. 2008

Advances in Land Remote Sensing

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U n c o r r e c t e d P r o o f 244 F. Jacob et al.Abstract Thermal Infra Red (TIR) Remote sensing allow spatializing various land surface temperatures: ensemble brightness, radiometric and aerodynamic temperatures, soil and vegetation temperatures optionally sunlit and shaded, and canopy temperature profile. These are of interest for monitoring vegetated land surface processes: heat and mass exchanges, soil respiration and vegetation physiological activity. TIR remote sensors collect information according to spectral, directional, temporal and spatial dimensions. Inferring temperatures from measurements relies on developing and inverting modeling tools. Simple radiative transfer equations directly link measurements and variables of interest, and can be analytically inverted. Simulation models allow linking radiative regime to measurements. They require indirect inversions by minimizing differences between simulations and observations, or by calibrating simple equations and inductive learning methods. In both cases, inversion consists of solving an ill posed problem, with several parameters to be constrained from few information. Brightness and radiometric temperatures have been inferred by inverting simulation models and simple radiative transfer equations, designed for atmosphere and land surfaces. Obtained accuracies suggest refining the use of spectral and temporal information, rather than innovative approaches. Forthcoming challenge is recovering more elaborated temperatures. Soil and vegetation components can replace aerodynamic temperature, which retrieval seems almost impossible. They can be inferred using multiangular measurements, via simple radiative transfer equations previously parameterized from simulation models. Retrieving sunlit and shaded components or canopy temperature profile requires inverting simulation models. Then, additional difficulties are the influence of thermal regime, and the limitations of spaceborne observations which have to be along track due to the temperature fluctuations. Finally, forefront investigations focus on adequately using TIR information with various spatial resolutions and temporal samplings, to monitor the considered processes with adequate spatial and temporal scales. IntroductionUsing TIR remote sensing for environmental issues have been investigated the last three decades. This is motivated by the potential of the spatialized information for documenting the considered processes within and between the Earth system components: cryosphere [1-2], atmosphere [3][4][5][6], oceans [7][8][9], and land surfaces [10]. For the latter, TIR remote sensing is used to monitor forested areas [11][12][13][14], urban areas [15][16][17], and vegetated areas. We focus here on vegetated areas, natural and cultivated. The monitored processes are related to climatology, meteorology, hydrology and agronomy: (1) radiation, heat and water transfers at the soil-vegetation-atmosphere interface [18][19][20][21][22][23][24]; (2) interactions between land surface and atmospheric boundary la...

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Section: Aerodynamic Temperaturementioning

confidence: 99%

Modeling and Inversion in Thermal Infrared Remote Sensing over Vegetated Land Surfaces

Jacob¹,

Schmugge

Olioso

et al. 2008

Advances in Land Remote Sensing

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“…At many locations SEBS underestimates the sensible heat flux; a phenomenon seen more often at high sensible heat flux rates when dealing with single-source models (Huntingford et al, 2000;Kustas et al, 1996). This is especially the case for sites that are characterized with a sparse vegetation cover under dry conditions.…”

Section: Empirical Scenariomentioning

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

Hydrol. Earth Syst. Sci.

100

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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.

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“…It has to be remembered that the soil temperatures over the top 0.3 m are essentially driven by the land surface temperature (LST) simulated by ORCHIDEE. This variable is well known to be affected by modelling assumptions and errors in the driving data (Huntingford et al, 2000). Previous studies have shown that reproducing remote sensed LST in land surface models is challenging (Barella-Ortiz et al, 2017).…”

Section: Convergence Of the Numerical Solutionsmentioning

confidence: 99%

Hydrological modelling on atmospheric grids; using graphs of sub-grid elements to transport energy and water

Polcher

Schrapffer²,

Dupont³

et al. 2022

Preprint

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Abstract. Land Surface Models (LSMs) use the atmospheric grid as their basic spatial decomposition because their main objective is to provide the lower boundary conditions to the atmosphere. Lateral water flows at the surface on the other hand require a much higher spatial discretization as they are closely linked to topographic details. We propose here a methodology to automatically tile the atmospheric grid into hydrological coherent units which are connected through a graph. As water is transported on sub-grids of the LSM, land variables can easily be transferred to the routing network and advected if needed. This is demonstrated here for temperature. The quality of the river networks generated, as represented by the connected hydrological transfer units, are compared to the original data in order to quantify the degradation introduced by the discretization method. The conditions the sub-grid elements impose on the time step of the water transport scheme are evaluated and a methodology is proposed to find an optimal value. Finally the scheme is applied in an off-line version of the ORCHIDEE LSM over Europe to show that realistic river discharge and temperatures are predicted over the major catchments of the region. The simulated solutions are largely independent of the atmospheric grid used thanks to the proposed sub-grid approach.

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Dual versus single source models for estimating surface temperature of African savannah

Cited by 14 publications

References 0 publications

Modeling and Inversion in Thermal Infrared Remote Sensing over Vegetated Land Surfaces

Modeling and Inversion in Thermal Infrared Remote Sensing over Vegetated Land Surfaces

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

Hydrological modelling on atmospheric grids; using graphs of sub-grid elements to transport energy and water

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