On the application of scintillometry over heterogeneous grids
2007
Ezzahar, J. | Chehbouni, Ghani | Hoedjes, Joost | Chehbouni, Ah | Laboratoire de Mécanique des Fluides et Energétique (LMFE) ; Faculté des Sciences Semlalia [Marrakech] ; Université Cadi Ayyad [Marrakech] (UCA)-Université Cadi Ayyad [Marrakech] (UCA) | Centre d'études spatiales de la biosphère (CESBIO) ; Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) ; Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) ; Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) ; Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) | Equipe Ecologie Végétale, Sol et Environnement ; Faculté des Sciences Semlalia [Marrakech] ; Université Cadi Ayyad [Marrakech] (UCA)-Université Cadi Ayyad [Marrakech] (UCA)
Summary In this paper the applicability of the Monin–Obukhov similarity theory (MOST) over heterogeneous terrain below the blending height is investigated. This is tested using two large aperture scintillometers (LAS), in conjunction with aggregation schemes to infer area-averaged refractive index structure parameters. The two LAS were operated simultaneously over the oliveyard of Agdal, located near Marrakech (Morocco). The Agdal olive yard is made up of two contrasted fields, or patches. The two sites are relatively homogeneous, but differ strongly in characteristics (mainly soil moisture status, and, to a lesser extent, vegetation cover). The higher soil moisture in the northern site creates heterogeneity at the scale of the entire olive yard (i.e. at grid scale). At patch scale, despite the complexity of the surface (tall, sparse trees), a good agreement was found between the sensible heat fluxes obtained from eddy-covariance systems and those estimated from the LAS. At grid scale, the aggregated structure parameter of the refractive index, simulated using the proposed aggregation model, behaves according to MOST. This aggregated structure parameter of the refractive index is obtained from measurements made below the grid scale blending height, and shows that MOST applies here. Consequently, scintillometers can be used at levels below the blending height. This is of interest, since strictly respecting the height requirements poses tremendous practical problems, especially if one is aiming to derive surface fluxes over large areas.
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