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Building a Field- and Model-based Climatology of Local Water and Energy Cycles in the Cultivated Sahel – Annual Budgets and Seasonality : Volume 11, Issue 5 (13/05/2014)

By Velluet, C.

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Book Id: WPLBN0004012097
Format Type: PDF Article :
File Size: Pages 56
Reproduction Date: 2015

Title: Building a Field- and Model-based Climatology of Local Water and Energy Cycles in the Cultivated Sahel – Annual Budgets and Seasonality : Volume 11, Issue 5 (13/05/2014)  
Author: Velluet, C.
Volume: Vol. 11, Issue 5
Language: English
Subject: Science, Hydrology, Earth
Collections: Periodicals: Journal and Magazine Collection (Contemporary), Copernicus GmbH
Historic
Publication Date:
2014
Publisher: Copernicus Gmbh, Göttingen, Germany
Member Page: Copernicus Publications

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Demarty, J., Cappelaere, B., Maidaji, B., Oï, M., Benarrosh, N., Velluet, C.,...Yahou, H. (2014). Building a Field- and Model-based Climatology of Local Water and Energy Cycles in the Cultivated Sahel – Annual Budgets and Seasonality : Volume 11, Issue 5 (13/05/2014). Retrieved from http://hawaiilibrary.net/


Description
Description: Université Montpellier 2, UMR HSM (CNRS/IRD/UM1/UM2), Montpellier, France. In the African Sahel, energy and water cycling at the land surface is pivotal for regional climate, water resources and land productivity, yet it is still extremely poorly documented. As a step towards a comprehensive climatological description of surface fluxes in this area, this study provides estimates of average annual budgets and seasonal cycles for two main land use types of the cultivated Sahelian belt, rainfed millet crop and fallow bush. These estimates build on the combination of a 7 year field dataset from two typical plots in southwestern Niger with detailed physically-based soil-plant-atmosphere modelling, yielding a continuous, comprehensive set of water and energy flux and storage variables over the 7 year period. In this study case in particular, blending field data with mechanistic modelling is considered as making best use of available data and knowledge for such purpose. It extends observations by reconstructing missing data and extrapolating to unobserved variables or periods. Furthermore, model constraining with observations compromises between extraction of observational information content and integration of process understanding, hence accounting for data imprecision and departure from physical laws. Climatological averages of all water and energy variables, with associated sampling uncertainty, are derived at annual to subseasonal scales from the 7 year series produced. Similarities and differences in the two ecosystems behaviors are highlighted. Mean annual evapotranspiration is found to represent ~82–85% of rainfall for both systems, but with different soil evaporation/plant transpiration partitioning and different seasonal distribution. The remainder consists entirely of runoff for the fallow, whereas drainage and runoff stand in a 40–60% proportion for the millet field. These results should provide a robust reference for the surface energy- and water-related studies needed in this region. The model developed in this context has the potential for reliable simulations outside the reported conditions, including changing climate and land cover.

Summary
Building a field- and model-based climatology of local water and energy cycles in the cultivated Sahel – annual budgets and seasonality

Excerpt
Sjöström, M., Ardö, J., Arneth, A., Boulain, N., Cappelaere, B., Eklundh, L., de Grandcourt, A., Kutsch, W. L., Merbold, L., Nouvellon, Y., Scholes, R. J., Schubert, P., Seaquist, J., and Veenendaal, E. M.: Exploring the potential of MODIS EVI for modeling gross primary production across African ecosystems, Remote Sens. Environ., 115, 1081–1089, doi:10.1016/j.rse.2010.12.013, 2011.; Sjöström, M., Zhao, M., Archibald, S., Arneth, A., Cappelaere, B., Falk, U., de Grandcourt, A., Hanan, N., Kergoat, L., Kutsch, W. L., Merbold, L., Mougin, E., Nickless, A., Nouvellon, Y., Scholes, R. J., Veenendaal, E. M., and Ardö, J.: Evaluation of MODIS gross primary productivity for Africa using eddy covariance data, Remote Sens. Environ., 131, 275–286, 2013.; Soegaard, H. and Boegh, E.: Estimation of evapotranspiration from a millet crop in the Sahel combining sap flow, leaf-area index and eddy-correlation technique, J. Hydrol., 166, 265–282, doi:10.1016/0022-1694(94)05094-e, 1995.; Taconet, O., Bernard, R., and Vidal-Madjar, D.: Evapotranspiration over an agricultural region using a surface flux/temperature model based on NOAA-AVHRR data, J. Clim. Appl. Meteorol., 25, 284–307, 1986.; Tanguy, M., Baille, A., González-Real, M. M., Lloyd, C., Cappelaere, B., Kergoat, L., and Cohard, J. M.: A new parameterisation scheme of ground heat flux for land surface flux retrieval from remote sensing information, J. Hydrol., 454–455, 113–122, doi:10.1016/j.jhydrol.2012.06.002, 2012.; Taylor, C. M., Gounou, A., Guichard, F., Harris, P. P., Ellis, R. J., Couvreux, F., and De Kauwe, M.: Frequency of Sahelian storm initiation enhanced over mesoscale soil-moisture patterns, Nat. Geosci., 4, 430–433, doi:10.1038/ngeo1173, 2011.; Taylor, C. M., de Jeu, R. A. M., Guichard, F., Harris, P. P., and Dorigo, W. A.: Afternoon rain more likely over drier soils, Nature, 489, 423–426, doi:10.1038/nature11377, 2012.; Timouk, F., Kergoat, L., Mougin, E., Lloyd, C. R., Ceschia, E., Cohard, J. M., de Rosnay, P., Hiernaux, P., Demarez, V., and Taylor, C. M.: Response of surface energy balance to water regime and vegetation development in a Sahelian landscape, J. Hydrol., 375, 178–189, doi:10.1016/j.jhydrol.2009.04.022, 2009.; Trenberth, K. E., Fasullo, J. T., and Kiehl, J.: Earth's global energy budget, B. Am. Meteorol. Soc., 90, 311–323, doi:10.1175/2008BAMS2634.1, 2009.; Tuzet, A., Castell, J. F., Perrier, A., and Zurfluh, O.: Flux heterogeneity and evapotranspiration partitioning in a sparse canopy: the fallow savanna, J. Hydrol., 188–189, 482–493, doi:10.1016/s0022-1694(96)03189-7, 1997.; Vandervaere, J. P., Peugeot, C., Vauclin, M., Angulo Jaramillo, R., and Lebel, T.: Estimating hydraulic conductivity of crusted soils using disc infiltrometers and minitensiometers, J. Hydrol., 188–189, 203–223, doi:10.1016/s0022-1694(96)03160-5, 1997.; van Genuchten, M. T.: A closed-form equation for predicting the hydraulic conductivity of unsaturated soils, Soil Sci. Soc. Am. J., 44, 892–898, doi:10.2136/sssaj1980.03615995004400050002x, 1980.; van Vliet, N., Reenberg, A., and Rasmussen, L. V.: Scientific documentation of crop land changes in the Sahel: a half empty box of knowledge to support policy?, J. Arid Environ., 95, 1–13, doi:10.1016/

 

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