Using a large aperture scintillometer for determining evapotranspiration of mountain foothills agriculture in the Rheraya catchment, Morocco

Assessing evapotranspiration at the basin scale is of crucial need for climate studies, weather forecasts, hydrological surveys, ecological monitoring, and water resource management. However, its determination is not an easy task especially for heterogeneous surfaces. Indeed, this heterogeneity, which is associated with the type of the vegetation canopy as well as the changes in topography, can generate a large variability of ET fluxes and thus limits the use of local scale measurement devices such as the Eddy Covariance system to measure ET. The main objective of this work was to investigate the potential of the scintillometer method to derive area-averaged sensible (H) and latent heat fluxes (LE) over mountain foothill agriculture, in the Rheraya catchments, Morocco. For this purpose, a Large Aperture scintillometer (LAS) was set up over an heterogeneous surface transect of about 1.4 km during years 2017 and 2018. Auxiliary data, including wind speed, air temperature soil heat flux and net radiation, were combined with the LAS measurements to derive ET at the transect scale. Also, the footprint of the LAS is analyzed in order to determine the surface sources of the LE fluxes. The results showed that the maximum values of latent heat flux are reached in spring and of sensible heat flux in summer, with values of about 456 and 420 W m^-2, respectively. Also, it can be concluded that the scintillometer is a device that can be considered as a potentially useful tool to derive turbulent surface fluxes over complex agricultural landscape.