The lockdown period (March–May 2020) during the COVID‐19 pandemic in Europe led to a reduction in the anthropogenic emissions of primary pollutants. For three‐quarters of over 1,100 available monitoring stations, the average nitrogen dioxide (NO₂) concentrations decreased by at least 2.7 μg·m⁻³ (or 25%) compared with the average concentrations recorded during the same period of the previous seven years. This reduction was not specific to urban or rural areas because the relative reduction was of similar magnitude in both areas. The ozone (O₃) response differed spatially, with positive anomalies in Northern Europe and negative anomalies in Southwestern Europe. Reduced cloudiness and related enhanced radiation in Northern Europe played a significant role in the increase of surface O₃ concentrations by shifting the photochemical partitioning between NO₂ and O₃ toward more O₃. The level of total oxidant (O_x = O₃ + NO₂) remained unchanged, except in Southwestern Europe where it decreased. Several episodes lasting a few days of a high level of total oxidants were observed in Northern Europe. The results illustrate the complexity of the atmospheric response to the unprecedented reduction in the emission of primary pollutants.

中文翻译：

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欧洲COVID-19锁定期间地表臭氧浓度对减排和气象的响应

在欧洲COVID-19大流行期间的封锁期（2020年3月至2020年5月）减少了人为排放的主要污染物。在1100多个可用监测站中，有四分之三的平均二氧化氮（NO ₂）浓度比前七年同期记录的平均浓度降低了至少2.7μg·m ^-3（或25％） 。这种减少并非特定于城市或农村地区，因为这两个地区的相对减少幅度相似。臭氧（O ₃）响应在空间上有所不同，北欧为正异常，而西南欧为负异常。北欧减少的云量和相关的辐射增强通过使NO ₂和O ₃之间的光化学分配向更多的O ₃转移，在表面O ₃浓度的增加中发挥了重要作用。总氧化剂水平（O _x = O ₃  + NO ₂）保持不变，但在西南欧有所下降。在北欧，发生了数天的总氧化剂持续数天的事件。结果表明，大气对初级污染物排放量空前减少的反应非常复杂。