On the use of land and ground data to improve integrated turbulent fluxes estimated from scintillometer measurements

Cohard, Jean-Martial, Guyot, Adrien, Anquetin, Sandrine, Galle, Sylvie and Seguis, Luc (2008). On the use of land and ground data to improve integrated turbulent fluxes estimated from scintillometer measurements. In: American Geophysical Union Fall Meeting, San Francisco, United States, (). 15-19 December 2008.

Author Cohard, Jean-Martial
Guyot, Adrien
Anquetin, Sandrine
Galle, Sylvie
Seguis, Luc
Title of paper On the use of land and ground data to improve integrated turbulent fluxes estimated from scintillometer measurements
Conference name American Geophysical Union Fall Meeting
Conference location San Francisco, United States
Conference dates 15-19 December 2008
Publication Year 2008
Sub-type Oral presentation
Open Access Status
Language eng
Abstract/Summary Scintillometry has been validated in many contexts of homogeneous and patchy land covers. Nevertheless natural landscapes are often more heterogeneous. This disables classical validation methodology which consists in comparison with aggregated Eddy correlation data. This study propose a simultaneous analysis of energy and water budget at hourly and daily scale to improve estimation of turbulent fluxes at scintillometer scale over a very heterogeneous area. Within the framework of the "AMMA-CATCH" program, a Large Aperture Scintillometer (LAS) has been installed in a small catchment (12 km2), located in the north Benin, a region exposed to soudano-sahelian climate. The site is instrumented with several ground stations to monitor the vadose zone, water table, precipitations and river discharge. Two case studies will be presented. The first one covers the end of the dry season. During this period two isolated rainfalls occurred which give a unique opportunity to study energy and water budgets simultaneously. The second one deals with the rainy season and offers to characterize evapotranspiration when vegetation suffers no water shortage. First, a methodology is proposed to aggregate surface parameters z0 and d, which are used to compute sensible heat flux from LAS data. Sensible heat fluxes from LAS and EC data are then compared. This shows a relatively good agreement where the scattering is mainly attributed to footprint variability. A relevant hourly residual latent heat flux is then obtained through the energy balance equation with careful attention brought to the aggregated net radiation and ground heat fluxes. The residual of the energy budget equation is then compared to soil water losses from vadose zone and water table in order to evaluate whether this estimation is consistent with the water budget of the ground. For the dry season period, the dynamic of ground water losses and evapotranspiration are well correlated. During the wet season we find a constant evaporative fraction which is relevant when vegetation runs into good transpiration conditions. Finally, this study shows how combined energy and water budget analysis can help to better understand water transfers at watershed scale.
Q-Index Code EX
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Conference Paper
Collection: School of Civil Engineering Publications
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Created: Thu, 05 Feb 2015, 13:09:27 EST by Adrien Guyot on behalf of School of Civil Engineering