Atmospheric controls on precipitation isotopes in North China and their response to record-breaking torrential rainfall

Abstract

Unlike the closer-to-consensus in tropical monsoon regions, the relationship between observed precipitation isotopes and hydroclimate conditions in North China is still unclear, leaving it uncertain whether these isotopes can serve as proxies for extreme events. Based on sub-event to daily precipitation samples collected between July 2022 and August 2023 in combination with published observations at two additional stations in North China, we explored the linkage between precipitation isotopes and hydroclimate conditions at the local and regional scales, focusing on their potential to record extreme rainfall events. We found that controls on isotopes exhibit a bifurcation between June to September (JJAS) and other months (Non-JJAS). Non-JJAS δ¹⁸O is strongly linked with temperatures at both local and regional scales. During JJAS, upstream accumulated rainfall along moisture transport pathways plays a dominant role. Interestingly, the lowest δ¹⁸O value occurred during the record-breaking rainfall in 2023 with a shift of −11.9 ‰ from the median. Another record-breaking event in 2012 corresponds to the lowest δ¹⁸O value (with a deviation of −9.2 ‰) in a daily dataset for Beijing from 2006 to 2015. However, another station at the south edge of the 2012 event shows relatively high isotopic values, likely due to the low upstream accumulated rainfall. These findings confirm the usefulness of water isotopes in North China as a proxy of regional rainfall. Further, we show the possibility of using high-resolution records to reconstruct past extreme rainfall events.