Stable Isotope Composition of Water Vapor and Weather in Typhoon Process Relationships: A Case Study of Typhoon Soudelor (1513)

Abstract

The stable hydrogen and oxygen isotopic composition of precipitation or water vapor not only shows the response to climate change on different time scales, but also has a strong relationship with typhoon extreme weather events. Typhoons usually bring destructive disasters, such as extreme rainstorms, strong winds, and storm surges, which have a significant social and economic impact worldwide. Therefore, the evolution of the typhoon weather process and the source of water vapor are worthy of attention. The stable isotope composition of water vapor can reflect more detailed weather process information than the stable isotope of precipitation, but available research on the stable isotope of water vapor in the atmosphere during a typhoon event is far less extensive and in-depth than that of precipitation. Based on the real-time high-frequency monitoring of water vapor stable isotopes of Nanjing before and after the impact of typhoon Soudelor (1513) combined with reanalysis data, the HYSPLIT model focused on analyzing the relationship between water vapor δ18O and weather processes and the water vapor indicated by excessive deuterium in the water vapor source. The results showed that the water vapor δ18O remained primarily constant and then decreased, while the excess deuterium of water vapor showed a completely opposite trend to that of water vapor δ18O. According to the change characteristics of water vapor δ18O, it is divided into three stages: In the first stage, the high δ18O level reflected the stable atmospheric conditions in Nanjing, and the low excess deuterium indicated that Nanjing was mainly influenced by marine water vapor. The low excess deuterium indicated that the water vapor source is consistent with the simulated water vapor source. In the second stage, the typhoon circulation and its residual pressure and the interaction of the cold air from the north to the south caused heavy precipitation in Nanjing. The combined effect of water vapor condensation and rainfall evaporation led to the continuous depletion of water vapor δ18O, and the high water vapor excess deuterium indicated that the Nanjing area was mainly affected by the ocean and the influence of local mixed water vapor. The high excess deuterium indicated that the water vapor source was consistent with the model. In the third stage, the mesoscale downdraft may have led to the extremely negative δ18O and high water vapor excess deuterium in the study area, which is not consistent with the water vapor source simulated by the model, indicating that the water vapor excess deuterium was not only affected by the horizontal water vapor transport source, but also by the downdraft. The analysis of time series data of water vapor stable isotopes revealed the relationship between local and microphysical processes and the evolution of water vapor stable isotope composition. A full understanding of the stable isotopic composition of modern water vapor under typhoon extreme events can assist with the understanding and interpretation of isotopic data in geological archives.

Keywords

• typhoon soudelor
• water vapor stable isotope
• weather process
• water vapor source
• nanjing