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

We present a 1-year long representative delta O-18 record of water vapor (delta O-18(v)) in Niamey (Niger) using the Wavelength Scanned-Cavity Ring Down Spectroscopy (WS-CRDS). We explore how local and regional atmospheric processes influence delta O-18(v) variability from seasonal to diurnal scale. At seasonal scale, delta O-18(v) 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 the dry season. During the monsoon season, delta O-18(v) 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 delta O-18(v) 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. delta O-18(v) 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. Citation: Tremoy, G., F. Vimeux, S. Mayaki, I. Souley, O. Cattani, C. Risi, G. Favreau, and M. Oi (2012), A 1-year long delta O-18 record of water vapor in Niamey (Niger) reveals insightful atmospheric processes at different timescales, Geophys. Res. Lett., 39, L08805, doi:10.1029/2012GL051298.