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 δ¹⁸O record of water vapor (δ¹⁸O_v) in Niamey (Niger) using the Wavelength Scanned-Cavity Ring Down Spectroscopy (WS-CRDS). We explore how local and regional atmospheric processes influence δ¹⁸O_v variability from seasonal to diurnal scale. At seasonal scale, δ¹⁸O_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, δ¹⁸O_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 δ¹⁸O_v modulations are also seen at the synoptic scale (5-9days) 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. δ ¹⁸O_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.