Radiative effects and feedbacks of anthropogenic aerosols on boundary layer meteorology and fine particulate matter during the COVID-19 lockdown over China

https://doi.org/10.1016/j.scitotenv.2022.160767Get rights and content

Highlights

  • Aerosol radiative and feedback effects during COVID-19 lockdown over China were explored.

  • Emission reduction led to a DRE anomaly up to 15 W m−2 and little IRE change in East China.

  • The lockdown induced an anomalous warming of 0.06 °C and 0.04 °C in North and South China.

  • Feedback-induced PM2.5 increase was reduced by 1.9 μg m−3 (40 %) in East China by lockdown.

Abstract

The COVID-19 epidemic has exerted significant impacts on human health, social and economic activities, air quality and atmospheric chemistry, and potentially on climate change. In this study, an online coupled regional climate–chemistry–aerosol model (RIEMS-Chem) was applied to explore the direct, indirect, and feedback effects of anthropogenic aerosols on radiation, boundary layer meteorology, and fine particulate matter during the COVID-19 lockdown period from 23 January to 8 April 2020 over China. Model performance was validated against a variety of observations for meteorological variables, PM2.5 and its chemical components, aerosol optical properties, as well as shortwave radiation flux, which demonstrated that RIEMS-Chem was able to reproduce the spatial distribution and temporal variation of the above variables reasonably well. During the study period, direct radiative effect (DRE) of anthropogenic aerosols was stronger than indirect radiative effect (IRE) in most regions north of the Yangtze River, whereas IRE dominated over DRE in the Yangtze River regions and South China. In North China, DRE induced larger changes in meteorology and PM2.5 than those induced by IRE, whereas in South China, the changes by IRE were remarkably larger than those by DRE. Emission reduction alone during the COVID-19 lockdown reduced PM2.5 concentration by approximately 32 % on average over East China. As a result, DRE at the surface was weakened by 15 %, whereas IRE changed little over East China, leading to a decrease in total radiative effect (TRE) by approximately 7 % in terms of domain average. The DRE-induced changes in meteorology and PM2.5 were weakened due to emission reduction, whereas the IRE-induced changes were almost the same between the cases with and without emission reductions. By aerosol radiative and feedback effects, the COVID-19 emission reductions resulted in 0.06 °C and 0.04 °C surface warming, 1.6 and 4.0 μg m−3 PM2.5 decrease, 0.4 and 1.3 mm precipitation increase during the lockdown period in 2020 in terms of domain average over North China and South China, respectively, whereas the lockdown caused negligible changes on average over East Asia.

Graphical abstract

The model simulated changes in (a) total radiative effect of anthropogenic aerosols at the surface (W m−2), and changes in the radiative feedback-induced (b) surface air temperature decrease (°C), (c) PBLH decrease (m), (d) surface PM2.5 concentration increase (μg m−3) due to anthropogenic emission reductions during the COVID-19 lockdown from 23 January to 8 April 2020. The changes are derived from the BASE case minus EXP case. The numbers in the upper right corner of each panel denote averages over East China during the study period.

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Keywords

Direct radiative effect
Indirect effect
Feedback
Anthropogenic aerosols
COVID-19
Boundary layer meteorology

Data availability

Data will be made available on request.

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