Coupling soil-vegetationatmosphere- transfer model with energy balance model for estimating energy and water vapor fluxes over an olive grove in a semi-arid region

Abstract

Simple soil-vegetation-transfer (SVAT) and energy balance models were used to estimate the surface turbulent fluxes (i.e. sensible and latent heat fluxes) over a complex olive grove using thermal infra-red surface temperature (TIRST). This approach used a dual source SVAT model to calculate the sensible heat fluxes from radiometric surface temperature. These fluxes were then used together with the estimates of the available energy also derived from TIRST to estimate the latent heat flux by applying the first law of thermodynamics i.e. the conservation of energy principle. The data used to validate this approach were collected over an irrigated olive grove site located in central Morocco near Marrakech. Mass and energy fluxes, as well as micrometeorological parameters, were continuously measured during the year 2003. The comparison between estimated and measured daily sensible heat fluxes yielded an acceptable agreement in spite of the complexity of the study surface with a correlation coefficient (R2=0.86) and root mean square error (RMSE) of 28 Wm-2. For the latent heat fluxes, the statistical result for the comparison between estimated and measured daily values showed a larger scatter than that revealed for the sensible heat fluxes (R2=0.75; RMSE=31.42 Wm-2). However, the correspondence is to be considered acceptable given the difficulty in estimating latent heat flux over such a complex field. Therefore, it can be concluded that, in spite of the simplicity of the proposed approach, it can be considered a suitable tool for estimating the turbulent fluxes using TIRST over complex surfaces.