2017年南京酸雨特征及连续发生的成因分析

利用南京市1992—2017年逐日酸雨监测数据、2017年大气污染物浓度和探空资料,研究了2017年连续酸雨出现特征及成因。结果表明:2017年南京酸雨发生频率38%,为近5 a来最低;年降水pH值为4.92,大于2014年,小于2015年和2016年;秋季酸雨发生频率最高、酸度最强,春季次之,夏季酸雨污染最轻;全年共出现了4次连续酸雨过程,高空多短波槽活动和低空切变的长时间维持为连续酸雨的产生提供了有利的环境背景,局地污染源、受低层风引导的外来污染物以及“假日效应”的叠加影响共同造成南京强酸雨的出现;此外,由于大气中水汽和能量的季节差异,也造成每次过程在降水强度、降水pH值上有所不同。

A study on characteristics of successive acid rain in Nanjing in 2017 and its causes

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.