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AGU: Geophysical Research Letters

 

Keywords

  • water stable isotopes
  • West African monsoon
  • convection

Index Terms

  • Biogeosciences: Isotopic composition and chemistry
  • Global Change: Water cycles
  • Atmospheric Processes: Tropical meteorology
  • Atmospheric Processes: Convective processes
  • Atmospheric Processes: Precipitation

Abstract

What controls the isotopic composition of the African monsoon precipitation? Insights from event-based precipitation collected during the 2006 AMMA field campaign

Camille Risi

Laboratoire de Météorologie Dynamique, IPSL, UPMC, CNRS, Paris, France

Sandrine Bony

Laboratoire de Météorologie Dynamique, IPSL, UPMC, CNRS, Paris, France

Francoise Vimeux

IRD-UR Great Ice/IPSL-LSCE (UMR CEA-CNRS-UVSQ), Gif-sur-Yvette, France

Luc Descroix

Laboratoire d'étude des Transferts en Hydrologie et Environnement, CNRS, Grenoble, France

Boubacar Ibrahim

Institut de Recherche pour le Développement, Niamey, Niger

Eric Lebreton

Laboratoire de Géographie Physique, CNRS, Meudon, France

Ibrahim Mamadou

Laboratoire de Géographie Physique, CNRS, Meudon, France

Benjamin Sultan

LOCEAN, IPSL, CNRS, Paris, France

The stable isotopic composition of the tropical precipitation constitutes a useful tool for paleoclimate reconstructions and to better constrain the water cycle. To better understand what controls the isotopic composition of tropical precipitation, we analyze the δ 18O and deuterium-excess of the precipitation of individual events collected in the Niamey area (Niger) during the monsoon season, as part of the 2006 AMMA field campaign. During the monsoon onset, the abrupt increase of convective activity over the Sahel is associated with an abrupt change in the isotopic composition. Before the onset, when convective activity is scarce, the rain composition records the intensity and the organization of individual convective systems. After the onset, on the contrary, it records a regional-scale intra-seasonal variability over the Sahel, by integrating convective activity both spatially and temporally over the previous days.

Received 5 September 2008; accepted 21 November 2008; published 27 December 2008.

Citation: Risi, C., S. Bony, F. Vimeux, L. Descroix, B. Ibrahim, E. Lebreton, I. Mamadou, and B. Sultan (2008), What controls the isotopic composition of the African monsoon precipitation? Insights from event-based precipitation collected during the 2006 AMMA field campaign, Geophys. Res. Lett., 35, L24808, doi:10.1029/2008GL035920.

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