Identification of processes that control the stable isotope composition of rainwater in the humid tropical West-Central Africa

JOURNAL OF HYDROLOGY

卷:584

Article

Nlend, B.^1,6,7  Celle-Jeanton, H.¹  Risi, C.²  Pohl, B.³  Huneau, F.^4,5  Boum-Nkot, S. Ngo⁶  Seze, G.²  Roucou, P.³  Camberlin, P.³  Etame, J.⁶  Ketchemen-Tandia, B.⁶ 

[1] Univ Bourgogne Franche Comte, UMR Chronoenvironm 6249, CNRS, 16 Route Gray, F-25030 Besancon, France

[2] Sorbonne Univ UPMC, Lab Meteorol Dynam, CNRS, IPSL, Paris, France

[3] Univ Bourgogne Franche Comte, Ctr Rech Climatol, UMR Biogeosci CNRS 6282, Dijon, France

[4] Univ Corse Pascal Paoli, Dept Hydrogeol, Campus Grimaldi,BP 52, F-20250 Corte, France

[5] CNRS, UMR SPE 6134, BP 52, F-20250 Corte, France

[6] Univ Douala, Fac Sci, POB 24157, Douala, Cameroon

[7] Hydrol Res Ctr, Cameroonian Inst Geol & Min Res, POB 4110, Yaounde, Cameroon

关键词: delta O-18;    Water vapor;    Convective activity;    GPCP precipitation;    Air back trajectory;   

DOI  :  10.1016/j.jhydrol.2020.124650

来源: Elsevier

【 摘 要 】

This study interprets 11 years (2006 to 2016) and 6 months (March to August in 2017) of respectively monthly and daily isotopic (delta D and delta O-18) monitoring of rain at Douala (Cameroon), a humid tropical station in Western Africa. The main scope is to analyze the climate controls on precipitation isotopes at different timescales. Firstly, we examine the annual cycles of delta O-18. Over the 11 years of survey, the annual cycle exhibits a W shape that is quite reproducible from year to year, with two minima in spring and autumn periods. Based on back trajectory calculations and remote sensing observations of water vapor isotopic composition, we show that the observed depletion in spring and autumn is due to strong convective activity along air mass trajectories. The same effect of convective activity can be observed at the daily timescale. At seasonal and daily time scales, the isotopic composition is also strongly tied to the convective organization and cloud types. More depleted precipitation is associated with larger areas of high clouds. Very low to low clouds are observed in July-August, mid-level to high clouds are dominant in June and high to very high clouds characterize March-April-May, thus explaining the enriched (depleted) values in summer (spring). Finally, this paper highlights the importance of large scale meteorological conditions controls on precipitation stable isotope composition in the Gulf of Guinea.

【 授权许可】

Free