Compositions of hydrogen and oxygen isotopes of precipitation in Xiamen, Southeast China Coast: Seasonal variations, synoptic processes, and typhoons impact

Abstract In this study, the δ 2 H and δ 18 O values of 162 precipitation samples (including 33 typhoon‐related samples), collected in Xiamen, southeast China coast, during June 2018 to August 2019, were investigated and analysed. The findings indicate an obvious seasonal variation in the δ 2 H and δ 18 O, primarily influenced by the East Asia Monsoon system with notable impact from typhoon occurrences during summer months. The synoptic time‐series variation of δ 2 H and δ 18 O exhibits greater complexity: three distinct types of isotopic variations were observed, indicating a clear influence from re‐evaporation processes and continuing equilibrium fractionation during condensation. The variation patterns of δ 2 H and δ 18 O were dominated by the local meteorological parameters that govern the re‐evaporation, whereas the overall isotopic composition of precipitation was primarily regulated by the moisture sources. The unique atmospheric structure and dynamic processes of typhoons led to a three‐stage variation of δ 2 H and δ 18 O in precipitation as the distance between the typhoon's centre and the study area changed. The consistent configuration of typhoon structure prompts analogous staged changes in different typhoon‐related precipitation. The trajectory of moisture source for typhoon‐related precipitation demonstrates a clear spiral structure (excluding typhoon Yutu ), revealing notable impacts from typhoon events.