HR: 0800h
AN: PP11B-0516    [Abstracts]
TI: Influence of Convection and Water Budget on Isotopic Composition of Precipitation (Oxygen 18 and Deuterium) During the West African Monsoon: Analysis of Rainwater Samples Collected in Niger During the 2006 AMMA Campaign
AU: * Risi, C M
EM: crlmd@lmd.jussieu.fr
AF: Laboratoire de Meteorolgie Dynamique, Case 99, 4, place Jussieu, Paris, 75005, France
AU: Vimeux, F
EM: vimeux@lsce.saclay.cea.fr
AF: IRD-UR Great Ice/IPSL-LSCE, CEA Saclay, Orme des Merisiers, Batiment 701, Gif-sur- Yvette, 91191, France
AU: Bony, S
EM: bony@lmd.jussieu.fr
AF: Laboratoire de Meteorolgie Dynamique, Case 99, 4, place Jussieu, Paris, 75005, France
AU: Descroix, L
AF: IRD Niamey, IRD Niamey BP 11416, Niamey, 11416, Niger
AU: Boubacar, I
AF: IRD Niamey, IRD Niamey BP 11416, Niamey, 11416, Niger
AU: Mamadou, I
AF: University Abdou Moumouni, IRD Niamey BP 11416, Niamey, 11416, Niger
AB: The isotopic composition of precipitation (Deuterium and Oxygen 18) is a valuable tool to reconstruct past climate variability and to better understand present and past water cycle. To better constrain the climate-isotopes and water budget-isotopes relationships, which are still poorly understood and quantified in the Tropics, precipitation samples from convective systems have been collected in the Niamey area (Niger) during the 2006 monsoon, as part of the AMMA (African Monsoon Multidisciplinary Analaysis) campaign. Isotopic composition (deuterium and deuterium excess) of precipitation are discussed in regard to the large amount of available atmospheric data collected during this campaign. On the one hand, event-scale samples were collected all along the monsoon season (from June to September 2006). The isotopic composition of rainfall reveals an abrupt change after the onset of the monsoon. The isotopic composition also depends on the degree of organization and intensity of the systems, time-averaged large-scale convective activity and low-level relative humidity. We investigate the relative influence of local convective processes, regional convective activity and large scale circulation on intra-seasonal to seasonnal time scale. On the other hand, rainwater from convective systems passing over Niamey were sampled at high frequency (time step as low as 5 minutes). Since convective processes (condensation, precipitation evaporation) are spatially differentiated in organized systems such as squall lines, we use this infra-event data to investigate the influence of convective processes on water isotopes, which is essential to better understand the climate-isotopes relationship. We also discuss the possibility of using the isotopic composition of rainfall to better constrain the water budget of squall lines (rain evaporation in particular).
DE: 1836 Hydrological cycles and budgets (1218, 1655)
DE: 1854 Precipitation (3354)
DE: 3314 Convective processes
DE: 3374 Tropical meteorology
DE: 4870 Stable isotopes (0454, 1041)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting