Preprints
https://doi.org/10.5194/egusphere-2024-1840
https://doi.org/10.5194/egusphere-2024-1840
05 Aug 2024
 | 05 Aug 2024

A-year Continuous Observations of Near-Surface Atmospheric Water Vapor Stable Isotopes at Matara, Sri Lanka

Yuqing Wu, Jing Gao, Aibin Zhao, Xiaowei Niu, Yigang Liu, Disna Ratnasekera, Tilak Priyadarshana Gamage, and Amarasinghe Hewage Ruwan Samantha

Abstract. Atmospheric water vapor stable isotopes are crucial for understanding hydrological cycle processes under climate change. This study presents a year-long in-situ monitoring of atmospheric water vapor stable isotopes (δ18O, δD) at Matara, Sri Lanka, from March 2020 to February 2021 to assess how oceanic sources and moisture transport influence coastal atmospheric moisture isotopic composition. We identified clear seasonal patterns in the isotopic composition, with δ18O, δD, and d-excess showing substantial variation between the southwest and northeast monsoon periods. The primary moisture sources were the Arabian Sea and the Indian Ocean during the southwest monsoon (May to September), characterized by depleted δ18O from -20.4 ‰ to -9.1 ‰. During the northeast monsoon dominated period, the northern Bay of Bengal, the Indian subcontinent, and Southeast Asia were primary moisture sources, displayed enriched δ18O (-23.9 ‰ to -7.5 ‰) and higher d-excess values (up to 25 ‰). The study also identified significant influences of sea surface temperature and sea surface relative humidity, on the isotopic composition of water vapor. Additionally, outgoing longwave radiation (OLR) is a significant index used to gauge the intensity of convective activity. Lower OLR values, indicative of stronger and deeper convection, were associated with more depleted δ18O in air masses. These findings help to improve the understanding of influences of the monsoon and local meteorological condition on water vapor isotopes in tropical region and provide new dataset on enhancing water vapor isotopic modeling or atmospheric processes projection in coastal regions.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Yuqing Wu, Jing Gao, Aibin Zhao, Xiaowei Niu, Yigang Liu, Disna Ratnasekera, Tilak Priyadarshana Gamage, and Amarasinghe Hewage Ruwan Samantha

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-1840', Anonymous Referee #1, 11 Sep 2024
    • AC1: 'Reply on RC2', Yuqing Wu, 26 Oct 2024
    • AC2: 'Reply on RC1', Yuqing Wu, 26 Oct 2024
  • RC2: 'Comment on egusphere-2024-1840', Anonymous Referee #2, 12 Sep 2024
    • AC1: 'Reply on RC2', Yuqing Wu, 26 Oct 2024
    • AC3: 'Reply on RC2', Yuqing Wu, 26 Oct 2024
Yuqing Wu, Jing Gao, Aibin Zhao, Xiaowei Niu, Yigang Liu, Disna Ratnasekera, Tilak Priyadarshana Gamage, and Amarasinghe Hewage Ruwan Samantha
Yuqing Wu, Jing Gao, Aibin Zhao, Xiaowei Niu, Yigang Liu, Disna Ratnasekera, Tilak Priyadarshana Gamage, and Amarasinghe Hewage Ruwan Samantha

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Short summary
This study monitored atmospheric water vapor isotopes for a year at Matara, Sri Lanka. It found clear seasonal variations in δ18O, δD, and d-excess. There showed depleted δ18O during the southwest monsoon, while had enriched δ18O and higher d-excess during the northeast monsoon. Sea surface condition and regional convective activity significantly influenced the isotopic compositions, improving understanding of monsoon and local meteorological condition impacts on tropical water vapor.