Derivation of Energy and Water Balance Parameters from ENVISAT AATSR Data across Savannah Volta Catchments in West Africa

Stephen Opoku-Duah, Daniel N.M. Donoghue & Tim P. Burt

Department of Geography, Durham University

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Abstract: This paper is an attempt to derive energy and water balance parameters from the ENVISAT Level 1B Advanced Along-Track Scanning Radiometer (AATSR) data across savannah Volta catchments in West Africa as one of the solutions for scarce spatial data sets needed for hydrological modelling. This was achieved through solution of the radiation and energy balance equations, which were computationally-driven by the Surface Energy Balance Algorithm for Land (SEBAL) algorithm. The results showed that the AATSR sensor is a potentially good source of key geophysical parameters (e.g. NDVI, net radiation [Rn], surface temperature [Ts] and evapotranspiration [ET]) needed as inputs to regional hydrological models. A multiple regression analysis showed quite strong correlations between these parameters (R2=0.61; p<0.001), which also compared well with published results over other semi-arid regions. However, comparison of AATSR estimates of ET with Landsat ETM+ and ground-based observations showed a wide deviation of about 2.0 mm day-1, which may be explained by differences in sensor calibration and spatial mismatch.

Keywords: Volta Savannah, Energy & Water Balance Parameters, AATSR, SEBAL


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