An image-based four-source surface energy balance model to estimate crop evapotranspiration from solar reflectance/thermal emission data (SEB-4S)

Abstract

International audienceA remote sensing-based surface energy balance model is developed to explicitly represent the energy fluxes of four surface components of agricultural fields including bare soil, unstressed green vegetation, non-transpiring green vegetation, and standing senescent vegetation. Such a four-source representation (SEB-4S) is achieved by a consistent physical interpretation of the edges and vertices of the polygon (named T − fvg polygon) obtained by plotting surface temperature (T) as a function of fractional green vegetation (fvg) and the polygon (named T − alpha polygon) obtained by plotting T as a function of surface albedo (alpha). To test the performance of SEB-4S, a T − alpha image-based model and a T − fvg image-based model are implemented as benchmarks. The three models are tested over a 16 km by 10 km irrigated area in northwestern Mexico during the 2007-2008 agricultural season. Input data are composed of ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) thermal infrared, Formosat-2 shortwave, and station-based meteorological data. The fluxes simulated by SEB-4S, the T − alpha image-based model, and the T − fvg image-based model are compared on seven ASTER overpass dates with the in situ measurements collected at six locations within the study domain. The evapotranspiration simulated by SEB-4S is significantly more accurate and robust than that predicted by the models based on a single (either T − fvg or T − alpha) polygon. The improvement provided with SEB-4S reaches about 100 W m−2 at low values and about 100 W m−2 at the seasonal peak of evapotranspiration as compared with boththe T − alpha and T − fvg image-based models. SEB-4S can be operationally applied to irrigated agricultural areas using high-resolution solar/thermal remote sensing data, and has potential to further integrate microwave-derived soil moisture as additional constraint on surface soil energy and water fluxes

Preferential cooling of hot extremes from cropland albedo management

“…1 is around 0.2, which is a relatively high albedo for an agricultural soil (due to the relatively high loam/low organic matter content in this soil). Previously reported in situ (11)(12)(13) and satellite (14,15) measurements suggest that the albedo of brown agricultural soils can be lower than 0.1, whereas soils covered with stubble can have albedos largely above 0.3, implying albedo differences…”

Intercomparison of four remote-sensing-based energy balance methods to retrieve surface evapotranspiration and water stress of irrigated fields in semi-arid climate

“…Larger errors for ICARE radiometric temperatures can be interpreted as a consequence of model error in the energy balance resolution. The radiative surface temperature in ICARE is determined as a linear combination of the aerodynamic canopy and soil temperatures (Model RTM-TIR0 of Merlin and Chehbouni, 2014), which are all computed from the resolution of the energy budget at each source (soil and canopy).…”

Diurnal Dynamics of Wheat Evapotranspiration Derived from Ground-Based Thermal Imagery

“…The diurnal and seasonal cycles of the surface temperature are affected by the relative efficiency of the components of the surface energy balance (SEB) in dissipating the available energy. Thus, SEB key components, such as the turbulent latent (λE) and sensible (H) heat flux, are frequently inferred from observations of the radiometric temperature over a wide range of spatial and temporal scales [1][2][3][4][5][6][7][8][9][10][11][12].…”