Precipitation Origins and Key Drivers of Precipitation Isotope (18O, 2H, and 17O) Compositions Over Windhoek

Kaseke, Kudzai Farai; Wang, Lixin; Wanke, Heike; Tian, Chao; Lanning, Matthew; Jiao, Wenzhe

Abstract

©2018. American Geophysical Union. All Rights Reserved. Southern African climate is characterized by large precipitation variability, and model precipitation estimates can vary by 70% during summer. This may be partly attributed to underestimation and lack of knowledge of the exact influence of the Atlantic Ocean on precipitation over the region. The current study models trajectories of precipitation events sampled from Windhoek (2012–2016), coupled with isotopes (δ18O, δ2H, δ17O, d, and δ′17O-δ′18O) to determine key local drivers of isotope compositions as well as infer source evaporative conditions. Multiple linear regression analyses suggest that key drivers of isotope compositions (relative humidity, precipitation amount, and air temperature) account for 47–53% of δ18O, δ2H, and δ17O variability. Surprisingly, precipitation δ18O, δ2H, and δ17O were independent of precipitation type (stratiform versus convective), and this may be attributed to greater modification of stratiform compared to convective raindrops, leading to convergence of isotopes from these precipitation types. Trajectory analyses showed that 78% and 21% of precipitation events during the period originated from the Indian and South Atlantic Oceans, respectively. Although precipitation from the Atlantic Ocean was significantly enriched compared to that from the Indian Ocean (p

• Journal Article Type: Article
• Acceptance Date: Jun 30, 2018
• Online Publication Date: Jul 6, 2018
• Publication Date: Jul 27, 2018
• Deposit Date: Feb 19, 2019
• Publicly Available Date: Feb 19, 2019
• Journal: Journal of Geophysical Research: Atmospheres
• Print ISSN: 2169-897X
• Electronic ISSN: 2169-8996
• Publisher: American Geophysical Union
• Peer Reviewed: Peer Reviewed
• Volume: 123
• Issue: 14
• Pages: 7311-7330
• DOI: https://doi.org/10.1029/2018JD028470
• Keywords: subtropical Atlantic ocean moisture, southern African precipitation, drought mechanisms, δ18O, δ2H, and δ17O
• Public URL: https://uwe-repository.worktribe.com/output/864062
• Publisher URL: https://doi.org/10.1029/2018JD028470
• Additional Information: Additional Information : An edited version of this paper was published by AGU. Copyright 2018 American Geophysical Union.
• Contract Date: Feb 19, 2019