Influence of ENSO Events on the Hydrogen (δ²H) and Oxygen (δ¹⁸O) Isotopic Values of Precipitation in Shanghai

An analysis of the effect of ENSO events with different strengths on the isotopic composition of precipitation is conducted based on test data for 206 precipitation samples collected from January 2012 to February 2017 in Shanghai coupled with the archives for Nanjing, Wuhan, Fuzhou, and Hong Kong from 1961 to 2012 from the Global Network of Isotopes in Precipitation (GNIP) database. During the research periods, the δD and δ¹⁸O values in precipitation are lower in summer and autumn but higher in winter and spring. The slope and intercept of the atmospheric precipitation lines during El Niño events are larger than during other times, while anti-temperature, precipitation amount, and vapor pressure effects are more significant than during La Niña events. The δ¹⁸O and deuterium excess values (value of d) of rainfall in Shanghai during El Niño and La Niña events of varied strengths have an obvious negative correlation with the oceanic Niño index (ONI), sea surface temperature anomaly (SSTA), and the extreme and cumulative values of ONI. Moreover, ENSO events are closely intertwined with the correlation between δ¹⁸O isotopic value in precipitation, ONI, and SSTA.