Modeling the impact of COVID-19 on air quality in southern California: implications for future control policies
Open Access
- 9 June 2021
- journal article
- research article
- Published by Copernicus GmbH in Atmospheric Chemistry and Physics
- Vol. 21 (11), 8693-8708
- https://doi.org/10.5194/acp-21-8693-2021
Abstract
In response to the coronavirus disease of 2019 (COVID-19), California issued statewide stay-at-home orders, bringing about abrupt and dramatic reductions in air pollutant emissions. This crisis offers us an unprecedented opportunity to evaluate the effectiveness of emission reductions in terms of air quality. Here we use the Weather Research and Forecasting model with Chemistry (WRF-Chem) in combination with surface observations to study the impact of the COVID-19 lockdown measures on air quality in southern California. Based on activity level statistics and satellite observations, we estimate the sectoral emission changes during the lockdown. Due to the reduced emissions, the population-weighted concentrations of fine particulate matter (PM2.5) decrease by 15 % in southern California. The emission reductions contribute 68 % of the PM2.5 concentration decrease before and after the lockdown, while meteorology variations contribute the remaining 32 %. Among all chemical compositions, the PM2.5 concentration decrease due to emission reductions is dominated by nitrate and primary components. For O3 concentrations, the emission reductions cause a decrease in rural areas but an increase in urban areas; the increase can be offset by a 70 % emission reduction in anthropogenic volatile organic compounds (VOCs). These findings suggest that a strengthened control on primary PM2.5 emissions and a well-balanced control on nitrogen oxides and VOC emissions are needed to effectively and sustainably alleviate PM2.5 and O3 pollution in southern California.Keywords
Funding Information
- National Aeronautics and Space Administration (TASNNP program)
- National Science Foundation (AGS-1660587)
- National Natural Science Foundation of China (41975178)
- Youth Innovation Promotion Association of the Chinese Academy of Sciences (n/a)
- State Key Laboratory of Resources and Environmental Information System (n/a)
- U.S. Department of Energy (Atmospheric System Research (ASR) programme)
- National Oceanic and Atmospheric Administration (DOE CPT program)
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