Water vapor isotopes indicating rapid shift among multiple moisture sources for the 2018/2019 winter extreme precipitation events in Southeast China

Abstract. In the East Asian monsoon region, winter extreme precipitation events occasionally occur and bring great social and economic losses. From December 2018 to February 2019, Southeast China experienced a record-breaking number of extreme precipitation events. In this study, we analyzed the variation of water vapor isotopes and their controlling factors during the extreme precipitation events in Nanjing, Southeast China. The results show that the variations of water vapor isotopes are closely linked to the change of moisture sources. Using a water vapor d-excess weighted trajectory model, we identified five most important moisture source regions: South China, East China Sea, South China Sea, Bay of Bengal, and Continental regions (Northwest China and Mongolia). Moreover, the variations of water vapor d-excess during a precipitation event reflect rapid shifts of moisture source regions. These results indicate that rapid shifts among multiple moisture sources are important conditions for sustaining wintertime extreme precipitation events over extended periods.