Scientific References

Peer Reviewed Literature: A 1-year long δ18O record of water vapor in Niamey (Niger) reveals insightful atmospheric processes at different timescales                

Authors Guillaume TremoyFrançoise Vimeux, Salla Mayaki, Idé Souley, Olivier Cattani, Camille Risi, Guillaume Favreau, Monique Oi
Presented at
Geophysical Research Letters http://dx.doi.org/10.1029/2012GL051298

Abstract

We present a 1-year long representative δ18O record of water vapor (δ18Ov) in Niamey (Niger) using the Wavelength Scanned-Cavity Ring Down Spectroscopy (WS-CRDS). We explore how local and regional atmospheric processes influence δ18Ov variability from seasonal to diurnal scale. At seasonal scale, δ18Ov exhibits a W-shape, associated with the increase of regional convective activity during the monsoon and the intensification of large scale subsidence North of Niamey during dry season. During the monsoon season, δ18Ov records a broad range of intra-seasonal modes in the 25-40-day and 15-25-day bands that could be related to the well-known modes of the West African Monsoon (WAM). Strong δ18Ov modulations are also seen at the synoptic scale (5-9 days) during winter, driven by tropical-extra-tropical teleconnections through the propagation of a baroclinic wave train-like structure and intrusion of air originating from higher altitude and latitude. δ18Ov also reveals a significant diurnal cycle, which reflects mixing process between the boundary layer and the free atmosphere during the dry season, and records the propagation of density currents associated with meso-scale convective systems during the monsoon season.                   

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