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Wageningen Universiteit Pays Bas (2005)

The surface energy balance over drying semi-arid terrain in West Africa

Schüttemeyer, D.

Titre : The surface energy balance over drying semi-arid terrain in West Africa

Auteur : Schüttemeyer, D.

Université de soutenance : Wageningen Universiteit

Grade : Doctor Thesis 2005

Résumé partiel
One of the fundamental aspects of current research in earth system science is the proper understanding of land-atmosphere interactions. The role of the land surface is crucial in the climate system, since a large fraction of incoming solar radiation passes through the atmosphere and is converted at the surface into turbulent fluxes. For numerous regions, including the semi-arid regions, only little knowledge is available about the diurnal and seasonal cycle of land surface interactions.The semi-arid areas pose a big challenge due to the large contrasts of dry and wet situations within a seasonal cycle.This is especially valid for the semi-arid region inWest Africa, since it is one of the most climatically sensitive and ecologically unstable regions in the world. The variability of weather and climate in the region is strongly influenced by complicated interactions and feedbacks between the land and the atmosphere. To analyze and to predict these interactions and feedbacks it is inevitable to measure and model the involved components. Since standard methods for this purpose are not always applicable to the heterogeneous surface inWest Africa, new measurement and modeling techniques have to be applied.
The overall objective of this thesis is to analyze and to model the land surface interactions intheVolta basin,West Africa, by using meteorological data obtained in the framework of the GLOWA-Volta project. A focus is put on diurnal and seasonal time scales. For measuring turbulent fluxes the key instrument is the large aperture scintillometer.This robust method yields area-averaged fluxes over complexterrain, which arerequired when analyzing meteorological data from heterogeneous surfaces. It is foundthat it is a suitable technique for the kind of environment also in comparison to different measuring techniques.

Mots clés : ATMOSPHERE / LAND / EVAPOTRANSPIRATION / ENERGY BALANCE / GHANA / BOUNDARY LAYER

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