Abstract:Based on the daily monitoring data of acid rain in Nanjing from 1992 to 2017 and the atmospheric pollutant concentration and sounding data in 2017, the characteristics of successive acid rain and its causes are studied in this paper. Results show that, the frequency of occurrence of acid rain in Nanjing was 38% in 2017, which was the lowest among the past five years, and the pH value of precipitation was 4.92, which is higher than that in 2014 and lower than those in 2015 and 2016. Both frequency and acidity of acid rain in 2017 peaked in autumn, and the pollution is relatively lighter in spring and the lightest in summer. There were four successive acid rain processes in 2017. It turned out that the maintenance of upper-level short-wave trough and low-level shear benefit the occurrence of acid rain. Moreover, the superimposed effect of local pollution brought by low-level wind, external pollution and the "holiday effect" further caused the occurrence of strong acid rain. Besides, since water vapor and energy in the atmosphere differ from seasons, the precipitation intensity and pH value of each acid rain process varied slightly.