29 Dec 2020
29 Dec 2020
Modeling the Impact of COVID-19 on Air Quality in Southern California: Implications for Future Control Policies
- 1Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
- 2Pacific Northwest National Laboratory, Richland, WA, USA
- 3Joint Institute for Regional Earth System Science and Engineering and Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
- 4Institute of Environment and Sustainability, University of California, Los Angeles, CA, USA
- 5Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- 6Nicholas School of the Environment, Duke University, Durham, NC, USA
- 7Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
- These authors contributed equally to this work.
- 1Key Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
- 2Pacific Northwest National Laboratory, Richland, WA, USA
- 3Joint Institute for Regional Earth System Science and Engineering and Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
- 4Institute of Environment and Sustainability, University of California, Los Angeles, CA, USA
- 5Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- 6Nicholas School of the Environment, Duke University, Durham, NC, USA
- 7Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
- These authors contributed equally to this work.
Abstract. In response to the Coronavirus Disease 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 on 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 (VOC). 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.
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Zhe Jiang et al.
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RC1: 'Review comments on “Modeling the impact of COVID-19 on air quality in Southern California: Implications for future control policies” by Jiang et al.', Anonymous Referee #3, 28 Jan 2021
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AC1: 'Reply on RC1', Bin Zhao, 10 Apr 2021
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AC1: 'Reply on RC1', Bin Zhao, 10 Apr 2021
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RC2: 'Review of “Modeling the Impact of COVID-19 on Air Quality in Southern California: Implications for Future Control Policies” authored by Jiang et al.', Anonymous Referee #1, 27 Feb 2021
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AC2: 'Reply on RC2', Bin Zhao, 10 Apr 2021
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AC2: 'Reply on RC2', Bin Zhao, 10 Apr 2021
Zhe Jiang et al.
Zhe Jiang et al.
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