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Understanding the Sahelian water budget through the isotopic composition of water vapor and precipitation

Risi, Camille and Bony, Sandrine and Vimeux, Françoise and Frankenberg, Christian and Noone, David and Worden, John (2010) Understanding the Sahelian water budget through the isotopic composition of water vapor and precipitation. Journal of Geophysical Research D, 115 (D24). Art. No. D24110. ISSN 0148-0227.

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The goal of this paper is to investigate the added value of water isotopic measurements to estimate the relative influence of large-scale dynamics, convection, and land surface recycling on the Sahelian water budget. To this aim, we use isotope data in the lower tropospheric water vapor measured by the SCIAMACHY and TES satellite instruments and in situ precipitation data from the Global Network for Isotopes in Precipitation and collected during the African Monsoon Multidisciplinary Analysis field campaign, together with water-tagging experiments with the Laboratoire de Météorologie Dynamique general circulation model (LMDZ) fitted with isotopes. We show that some isotopic biases in LMDZ reveal the misrepresentation of dehydrating processes that would be undetected without isotopic measurements. In dry regions, the vapor isotopic composition is primarily controlled by the intensity of the air dehydration. In addition, it may also keep some memory of dehydration pathways that is erased in the humidity distribution, namely the relative contribution of dehydration in the tropical upper troposphere versus midlatitudes. In wet regions, vapor and rain isotope compositions are primarily controlled by changes in convection, through rain reevaporation and through the progressive depletion of the vapor by convective mixing along air mass trajectories. Gradients in vapor isotope composition along air mass trajectories may help estimate continental recycling intensity, provided that we could quantify the effect of convection on the isotopic composition of water vapor.

Item Type:Article
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URLURL TypeDescription Information
Risi, Camille0000-0002-8267-453X
Frankenberg, Christian0000-0002-0546-5857
Worden, John0000-0003-0257-9549
Additional Information:© 2010 American Geophysical Union. Received 28 June 2010; revised 13 September 2010; accepted 29 September 2010; published 23 December 2010. We gratefully thank Luc Descroix, Boubacar Ibrahim, Eric Lebreton, and Ibrahim Mamadou for the rain sampling in the Niamey region; S. Falourd and B. Minster for helping with the isotopic measurements. Based on a French initiative, AMMA was built by an international scientific group and is currently funded by a large number of agencies, especially from France, the United Kingdom, the United States and Africa. It has been the beneficiary of a major financial contribution from the European Community’s Sixth Framework Research Programme. Detailed information on scientific coordination and funding is available on the AMMA International web site http://www.amma‐ This work was funded by the IPSL project, AMMA API and LEFE/MISTERRE national programme. We thank three anonymous reviewers for their constructive comments.
Funding AgencyGrant Number
European Community Sixth Framework Research ProgrammeUNSPECIFIED
Issue or Number:D24
Record Number:CaltechAUTHORS:20150511-152827360
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Official Citation:Risi, C., S. Bony, F. Vimeux, C. Frankenberg, D. Noone, and J. Worden (2010), Understanding the Sahelian water budget through the isotopic composition of water vapor and precipitation, J. Geophys. Res., 115, D24110, doi:10.1029/2010JD014690
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57424
Deposited By: Tony Diaz
Deposited On:11 May 2015 22:53
Last Modified:09 Mar 2020 13:19

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