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Communication incl. Poster: BibTeX citation key:  Doukoure
Doukouré, M., Anquetin, S. & Cohard, J.-M. 2009. Turbulent flux variability within the heterogeneous ARA catchment in Benin: A numerical study using the LES Meso-NH model. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: roussot 2009-11-04 19:54:58
Categories: Atmospheric processes, Land surface processes, Land surface-atmosphere feedback
Keywords: Atmospheric Boundary Layer, Clouds - Convection
Creators: Anquetin, Cohard, Doukouré
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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One of the goals of the AMMA/CATCH experiment is to characterize the water resources change and its interaction with agricultural practice. In this context instrumentation has been deployed to measure hydrological budget components from local to several hundreds of km2 scales with a focus on small catchments (~10 km2). One of the challenging points is the characterisation of the evapotranspiration at each scale. Indeed, Eddy-correlation techniques often fail to provide confident turbulent fluxes because of large heterogeneity of natural surface and orography. These local measurements can not be extended at large scale for the same reasons. In the other hand, scintillometric tools provide aggregated fluxes but need more advanced footprint analysis. Detailed studies on flux variability are then necessary to interpret measurements and to understand the impact of surface heterogeneity on these measurements.
The purpose of this study is to characterize spatial flux variability within the little heterogeneous ARA catchment (~12 km2) in Benin. Our approach is based on LES simulations forced by constant meteorological conditions and real surface characteristics (orography, vegetation cover, temperature, humidity). Simulations are performed with the non-hydrostatic Meso-NH model (Lafore et al., 1998) where turbulent fluxes are calculated interactively with the distributed ISBA SVAT model (Noilhan et al., 1989).
The first results show the impact of the orography on the local atmospheric flow and the induced turbulent structures. Several orography configurations have been implemented to analyse the impact of resolution on turbulent fluxes. The first one is extracted from the GTOPO30 database at 1 km scale and the second from the SRTM database (30m). The impact of orography on surface wind is analysed for different synoptic wind directions. Finally, it is shown how these results can be used to precise footprint analysis for scintillometric observations realized on the catchment (Guyot et al., 2009).
Added by: roussot