杭州临安一次严重大气污染过程的气温与污染物特征

为了研究严重污染过程大气温度与污染物的特征，选取杭州临安近3 a中一次严重大气污染过程，利用MTP5温度廓线仪数据和空气质量监测数据进行统计分析，探索气温和污染物变化特征。结果表明:①逆温现象主要集中在清晨和傍晚，全天温差超过7.0℃未出现逆温现象，逆温底高和顶高通常为400和700 m。②逆温厚度最大值为700.0 m，平均逆温厚度为359.9 m。逆温温差最大值为3.7℃，平均逆温为0.7℃。逆温温差与逆温厚度极显著相关（R2=0.914，P＜0.01）。③细颗粒物（PM_2.5）和可吸入颗料物（PM₁₀）是主要污染物。该次严重污染期间，PM_2.5和PM₁₀质量浓度分别超过115和250 μg·m-3；二氧化硫、一氧化碳、臭氧、二氧化氮等4种气体在这次污染过程中始终处在优良状态。④PM_2.5和PM₁₀与逆温底高具有极显著正相关，逆温顶高与2种颗粒物质量浓度不存在显著相关。造成污染的原因之一是逆温底高度下降，垂直方向上颗粒物扩散受阻而产生大量聚集。

Atmospheric temperature and pollutants on heavy pollution days in Lin'an,Hangzhou

To determine the atmospheric temperature and pollutant characteristics during periods of heavy pollution, a statistical analysis using data collected by MTP5 Temperature Profiler and Air Quality Monitoring System was made during serious air pollution incidents in Lin'an over the three years from 2015-2018. A correlation analysis was also conducted, which used statistical time series analysis. Results of the analysis showed that (1) temperature inversions were concentrated in the evening and early morning. When temperature differences between early morning and evening were over 7℃ all day, daytime temperature inversions did not appear. Inversion heights were usually 400 m at the base and 700 m at the top. (2) As for inversion thickness, the maximum was 700 m with an average of 359.9 m. The maximum temperature difference of an inversion was 3.7℃ with average of 0.7℃. The range of temperature had a highly significant correlation with inversion thickness (R2=0.914, P < 0.01). (3) Particulate matter PM_2.5 and PM₁₀ were the major pollutants. The concentration of PM_2.5 exceeded 115 μg·m-3 and PM₁₀ exceeded 250 μg·m-3. Four gases, SO₂, CO, O₃, and NO₂, always had good quality during the pollution occurrences. (4) The base height of the inversion had highly significant correlations with PM_2.5 (P < 0.01) and PM₁₀ (P < 0.01) concentrations; however, no significant correlations were found for the top of the inversion. Thus, the cause of pollution was determined to be a decrease in the temperature inversion and the mass accumulation of particulate matter in the vertical direction.