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A 1‐year long δ 18 O record of water vapor in Niamey (Niger) reveals insightful atmospheric processes at different timescales
Author(s) -
Tremoy Guillaume,
Vimeux Françoise,
Mayaki Salla,
Souley Ide,
Cattani Olivier,
Risi Camille,
Favreau Guillaume,
Oi Monique
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl051298
Subject(s) - monsoon , climatology , diurnal cycle , atmospheric sciences , subsidence , environmental science , baroclinity , water vapor , dry season , altitude (triangle) , latitude , synoptic scale meteorology , wet season , teleconnection , middle latitudes , geology , geography , meteorology , el niño southern oscillation , structural basin , paleontology , geometry , cartography , mathematics , geodesy
We present a 1‐year long representative δ 18 O record of water vapor ( δ 18 O v ) in Niamey (Niger) using the Wavelength Scanned‐Cavity Ring Down Spectroscopy (WS‐CRDS). We explore how local and regional atmospheric processes influence δ 18 O v variability from seasonal to diurnal scale. At seasonal scale, δ 18 O 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, δ 18 O 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 δ 18 O 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. δ 18 O 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.