Response of surface ozone concentration to emission reduction and meteorology during the COVID‐19 lockdown in Europe

Abstract

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 (NO 2 ) 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 (O 3 ) 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 O 3 concentrations by shifting the photochemical partitioning between NO 2 and O 3 toward more O 3 . The level of total oxidant (O x = O 3 + NO 2 ) 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.

The role of emission reductions and the meteorological situation for air quality improvements during the COVID-19 lockdown period in central Europe

“…First of all, this is surprising because 2020 was comparably sunny and dry, which should favour ozone formation. The latter was also stated by Deroubaix et al (2021) and in their studies about the COVID19 lockdown effects on air quality. However, advection of relatively clean air from Scandinavia into the north-eastern part of the model domain led to lower ozone concentrations particularly in the second half of April.…”

“…Meteorological data for the CMAQ model were provided by a simulation of the COSMO model (Baldauf et al, 2011;Doms et al, 2011;Doms and Schättler, 2002) applying the version COSMO5-CLM16 (climate mode; Rockel et al, 2008). To simulate the radiative transfer as realistic as possible, an extension of the COSMO model for the MACv2 transient aerosol climatology was used.…”

“…The response of ozone concentrations to emission changes is therefore not straightforward to predict. Also long-range transport, which was neglected here, may play role (see also Deroubaix et al, 2021, andMertens et al, 2021).…”

Urban Air Chemistry in Changing Times

“…The applications and sensitivity of the model predictions can be evaluated for chemistry, meteorology and emissions assuming changes in past conditions and expected in the future. Examples of such studies include (a) the intercomparison of truncated chemical reaction mechanisms [34,68,69]; (b) the investigation of "sudden" emission reduction (e.g., the COVID-19 experience [70,71]); (c) the influence on urban air chemistry considering the meteorology of "the street canyon effect" [72]; (d) the sensitivity to climate conditions [73]; and (e) projections of urban-or city-specific O 3 trends to 2100 varying O 3 background [74,75]. Each of these computer-based experiments add insight into gas phase and in some cases particle chemistry in the light of meteorological and emission-deposition conditions.…”

Ozone Anomalies in the Free Troposphere During the COVID‐19 Pandemic

“…Biogenic emissions are calculated online from the Model of Emissions of Gases and Aerosols from Nature (Guenther et al, 2012). Daily biomass burning emissions are based the Quick-Fire Emissions Dataset (Darmenov & da Silva, 2014) include, for example, the 2019/2020 large fires in California, Colorado, and Australia. Deposition of gases and aerosols are calculated through an active coupling between the atmosphere and the Community Land Model version 5 (Lawrence et al, 2019 Doumbia et al (2021).…”