Monitoring Characteristics of Hydrogen and Oxygen Isotopes in Precipitation of Nanjing

Abstract

With the climate change, extreme precipitation events become more and more frequent. It is particularly important to explore the characteristics of different precipitation types for the study of local precipitation process and water cycle. In order to explore the isotopic characteristics of different precipitation types, especially the relationship between the isotopic characteristics of tropical cyclone precipitation and its moving path, the characteristics of precipitation in Nanjing from July 2018 to June 2019 are analyzed based on the precipitation isotopic composition data and the meteorological data from China Meteorological Administration. The results indicate that, in general, the stable hydrogen and oxygen isotopic compositions of precipitation in Nanjing are more depleted in monsoon wet season and more enriched in non-monsoon wet season. After classifying the precipitation types, it is found that the intensity of tropical cyclone and Meiyu precipitation is high, and the hydrogen and oxygen isotopic compositions are seriously depleted; while the intensity of other precipitation are relatively weak, and the hydrogen and oxygen isotopic compositions are relatively rich. The deuterium excess value of tropical cyclone precipitation is usually less than the global average (10‰), which may be caused by the fast speed and short path of tropical cyclones from the eastern sea surface. The deuterium excess value of Meiyu precipitation is slightly higher than the global average, which may be influenced by persistent stationary fronts, the long and slow water vapor transport distance, and strong land evaporation. Other precipitation deuterium excesses are much larger than the global average, and this may be due to the more complex effects of land surface evaporation. Detailed analysis also indicates that, among the tropical cyclone influencing the precipitation of Nanjing, those directly landing in China from the ocean lead to lower deuterium excess values from 7.5‰ to 8.6‰. But for those landing on the southern Japan first and then in China, like Typhoon Jongdari (1812), the deuterium excess value of precipitation is much greater than 10‰, indicating that it is significantly affected by the land.

Keywords

• precipitation
• stable isotopes of hydrogen and oxygen
• deuterium excess
• sources of water vapor
• tropical cyclones