Variations of stable isotope in Typhoon Lupit (2021) rainfall and its response to upstream convective processes

Abstract

Typhoons produce a large amount of rainfall with a highly depleted isotopic composition. However, the mechanisms of isotope fractionation during typhoons remain poorly understood. Here, we present the hourly resolution isotope composition of rainfall during Typhoon Lupit (2021) in Fuzhou, on the southeast coast of China, to better understand these processes. Our results showed that the rainfall of Typhoon Lupit had significant fluctuations in δ 18 O values, ranging from À20.1‰ to À6.3‰, and exhibited a three-stage variation with distinctly negative δ 18 O values in the second stage. In the first stage of Lupit, water vapour originated primarily from the nearby sea area, which did not undergo sustained convective activity, resulting in relatively enriched δ 18 O values. In the second stage, the δ 18 O values were extremely negative mainly because of the accumulated convective activity and continuous precipitation as they travelled towards the centre of the typhoon. In the third stage, the mixing of more localized and nearby sea water vapour caused an increase in the δ 18 O values. In summary, the three-stage characteristics of Typhoon Lupit were largely caused by the integration of accumulated convective activity and moisture sources.Our findings reveal how upstream rainout affects the isotopic behaviour of rainfall and may have implications for understanding the dynamics of typhoon rainfall isotopes.

17O‐Excess in Tropical Cyclones Reflects Local Rain Re‐Evaporation More Than Moisture Source Conditions

“…Similar relationships between δ 18 O, 17 O‐excess, and d‐excess are commonly observed for waters in highly evaporative environments (Aron, Levin, et al., 2021; A Landais et al., 2010). Were there no re‐evaporation effect, δ 18 O would have been controlled mainly by the Rayleigh processes during these tropical cyclone storms (Sun et al., 2022; Yang et al., 2023), which would have limited impacts on d‐excess or 17 O‐excess values (Aron, Levin, et al., 2021; Dütsch et al., 2017; Luz & Barkan, 2010; Z. Xia et al., 2023). Therefore, condensation and Rayleigh distillation cannot explain these observed relationships among δ 18 O, 17 O‐excess, and d‐excess.…”