Did the COVID-19 pandemic response reduce Free Tropospheric Ozone across the Northern Hemisphere?

Throughout spring and summer 2020, ozone stations in the northern extratropics recorded unusually low ozone in the free troposphere. From April to August, and from 1 to 8 kilometers altitude, ozone was on average 7% (≈4 ppbv) below the 2000 to 2020 climatological mean. Such low ozone, over several months, and at so many stations, has not been observed in any previous year since at least 2000. Atmospheric composition re-analyses from the Copernicus Atmosphere Monitoring Service and simulations from the NASA GMI model indicate that the large 2020 springtime ozone depletion in the Arctic stratosphere has contributed less than one quarter to the observed tropospheric anomaly. The observed anomaly is consistent with recent model simulations, which assume emission reductions consistent with the COVID-19 societal impacts (Weber et al., 2020). COVID-19 related emission reductions appear to be the major cause for the observed low free tropospheric ozone in 2020.

2020年春夏期间，北半球温带地区的臭氧监测站记录到自由对流层（free troposphere）中的臭氧浓度异常偏低。4月至8月期间，在1至8公里的高度范围内，臭氧浓度平均比2000-2020年的气候平均值低7%（约4 ppbv）。至少自2000年以来，如此持续数月、且在众多站点观测到的臭氧浓度偏低现象，在以往任何年份均未出现过。哥白尼大气监测服务的大气成分再分析数据，以及美国国家航空航天局（NASA）GMI模型的模拟结果表明，2020年春季北极平流层（stratosphere）出现的大规模臭氧损耗，对观测到的对流层异常的贡献不足四分之一。观测到的异常与近期模型模拟结果一致，这些模拟假设了与COVID-19社会影响相符的排放减少情景（Weber等人，2020）。与COVID-19相关的排放减少似乎是2020年观测到的自由对流层臭氧浓度偏低的主要原因。