Plateau Atmospheric and Environment Key Laboratory of Sichuan Province, College of Atmosphere Sciences, Chengdu University of Information Technology, Chengdu 610225, China.
Key Laboratory for Atmospheric Chemistry, Chinese Academy of Meteorological Sciences, CMA, Beijing 100081, China.
Sci Total Environ. 2018 Sep 1;635:576-585. doi: 10.1016/j.scitotenv.2018.04.122. Epub 2018 Apr 24.
The Sichuan and Chongqing regions suffer from severe haze weather in winter due to the unfavourable atmospheric diffusion conditions. Reanalysis and precipitation datasets were applied in this study to calculate and distinguish air stagnation events using a developed criterion, and the impacts of the occurrence of air stagnation events on air quality were analysed in combination with the PM concentration data for the winters of 2013-2016. The highest occurrence frequency of air stagnation events was observed in 2013, and the lowest, 2015. The meteorological conditions during winter in the Sichuan Basin were inclined to form unfavourable atmospheric diffusion conditions, and the occurrence frequency of air stagnation days was up to 76.6% on average during the four winters. The effects of air stagnation events on air quality were most obvious in the western and southern Sichuan Basin. The mean concentrations of PM during air stagnation days were higher by 41.9% than those during non-air stagnation days. The PM concentrations were adjusted using the favourable atmospheric diffusion conditions in 2015 as a baseline to quantify the PM contribution to the improvement of air quality in the other years, which revealed that the level of PM in the Sichuan and Chongqing regions was declining at a rate of approximately 10.7% overall during the winters of 2013-2016, implying that the air pollutant reduction measures have been highly effective. Furthermore, the occurrence frequency of air stagnation days and events were increased in recent ten years of 2007-2016, with linear slopes of 0.61yr and 0.26yr, respectively. The study revealed that the government might face a greater challenge in improving the air quality over winter and should pay more attention to reduction of pollutant emission in areas of Chengdu, Chongqing and cities in the south of the Sichuan Basin.
四川和重庆地区冬季由于不利的大气扩散条件，易发生雾霾天气。本研究应用再分析资料和降水资料，采用制定的判据计算并区分了大气静稳事件，并结合 2013-2016 年冬季 PM 浓度资料分析了大气静稳事件对空气质量的影响。结果表明，2013 年大气静稳事件发生频率最高，2015 年最低。四川盆地冬季气象条件不利于大气扩散，4 个冬季平均大气静稳日数频率高达 76.6%。大气静稳事件对空气质量的影响在四川盆地西部和南部最为明显。静稳天气日 PM 浓度比非静稳天气日平均高 41.9%。以 2015 年有利大气扩散条件为基准，调整大气静稳事件对空气质量的影响，定量分析了其他年份 PM 对空气质量改善的贡献，结果表明，2013-2016 年冬季四川和重庆地区 PM 浓度总体呈下降趋势，降幅约为 10.7%，表明大气污染物减排措施非常有效。此外，2007-2016 年近 10 年来大气静稳日数和事件的发生频率呈增加趋势，线性斜率分别为 0.61yr 和 0.26yr。研究表明，政府在改善冬季空气质量方面可能面临更大的挑战，应更加关注成都、重庆和四川盆地南部城市等地区的污染物减排。
