基于WRF-Chem和EMI指数的新冠肺炎疫情期间沈阳市大气污染物浓度变化原因分析

Causes of variation of air pollutant concentration in Shenyang during the COVID-19 epidemic based on WRF-Chem and EMI-index

利用2015-2020年沈阳市空气质量监测数据、地面气象观测资料、环境气象评估指数(EMI)产品、NCEP再分析资料及WRF-Chem数值模式,分析新冠肺炎疫情防控期间沈阳市主要大气污染物和气象要素的变化情况,研究空气质量对污染物减排和气象要素变化的响应.结果表明:疫情防控导致沈阳市PM_(2.5)、PM10和NO_(2)质量浓度下降,但O_(3)质量浓度小幅增加;PM_(2.5)和NO_(2)对人为减排的响应更敏感;防控期内沈阳市气象条件有利于污染物的清除,气象条件使PM_(2.5)质量浓度下降16.37%,防控减排措施导致PM_(2.5)质量浓度下降22.96%;在疫情防控的背景下,不利的气象条件和污染物排放的突然增加共同造成重污染天气发生,其中不利气象条件的贡献大于排放增加的贡献;减排措施对防控期间重污染天气过程污染物峰值浓度有明显的削弱作用.

Using air quality monitoring data, surface meteorological observational data, meteorological environment assessment index(EMI-index) products, National Centers for Environmental Prediction(NCEP) reanalysis data and output of the Weather Research and Forecasting model coupled to Chemistry(WRF-Chem) from 2015 to 2020 in Shenyang, we analyzed the variation of criteria air pollutants and meteorological elements in Shenyang during the epidemic of COVID-19 and evaluated the response of air quality to emission reduction and meteorological conditions. The results showed that mass concentrations of PM_(2.5), PM10, and NO_(2) in Shenyang during the epidemic of COVID-19 decreased, while O_(3) concentration slightly increased. PM_(2.5) and NO_(2) were more sensitive to anthropogenic emission reduction. PM_(2.5) concentration decreased by 16.37% due to meteorological conditions and by 22.96% due to the prevention and control measures. Under the background of prevention and control measures, adverse meteorological conditions and sudden enhancement in pollutant emissions caused heavy pollution periods, among which adverse meteorological conditions played a more important role. Meanwhile, the emission reduction measures significantly weakened the peak of pollutant concentration in heavy pollution events.