Extracted COVID-19 signals of stay-home or lockdown effects on air pollution with the NASA's MERRA-2 re-analysis data
Abstract
The COVID-19 pandemic created a unique experiment and has both short and long-term impacts on earth-atmosphere system. Air pollution change is one of the discussed impacts in our scientific community. To assess the COVID-19 impact on air quality (here, mostly for aerosols and PM2.5), we analyzed the NASA's MERRA-2 re-analysis data of atmospheric aerosols and PM2.5 for the period of 2017 to 2020. The initial period of analysis is focused on the month of January to April. Data from year 2017-2019 were used as reference (called baseline) to compare with year 2020 data to estimate changes due to reduced emissions under covid-19 related restrictions in place. The Aerosol Optical Depth (AOD) is used to assess the atmospheric columnar loading of aerosols whereas PM2.5 mass concentration is used to assess the air quality near the surface. During the time period in January-April, some regions over Eurasia always showed the clear negative anomaly of AOD and PM2.5 compared to the 2017-2019 mean data. For example, over North Africa and India, the spatial patterns of the negative PM2.5 anomaly look similar to those of dust mass concentration in PM2.5 size. This means the negative anomaly signals due to lockdown over those regions were significantly affected by dust (i.e., natural aerosol variations). In addition to total PM2.5, MERRA-2 also provide aerosols' components, which are used to further analyzed the impact on specific aerosols types. We calculated the partial PM2.5 excluding the natural aerosols (dust and sea salt), the decline in aerosols in year 2020 became clearer. In East Asia, the areas with the partial PM2.5 reductions (i.e., the negative anomaly) were seen over the southeast of China in February. Then, the areas expanded to the northeast, Korea, and Japan in March. In April, a strong negative anomaly of the partial PM2.5 was seen from the eastern edge of Eurasia to Hokkaido (the northern part of Japan). However, we should be careful to discuss the stay-home or lockdown effect on air quality based on the purely air quality data alone because the observed aerosol variations can come from multiple factors including reduction in emissions, increased in natural aerosols (biomass burning and dust) and restricted human activities. We will present global analysis and quantify impacts due to COVID-19 around global regions in this study.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA057...08Y
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0240 Public health;
- GEOHEALTH