With the current COVID-19 pandemic being spread all over the world, lockdown measures are being implemented, making air pollution levels go down in several countries. In this context, the air quality changes in the highly populated and trafficked Brazilian states of São Paulo (SP) and Rio de Janeiro (RJ) were addressed using a combination of satellite and ground-based daily data analysis. We explored nitrogen dioxide (NO${}_2$) and fine particulate matter (PM${}_{2.5}$) daily levels for the month of May from 2015–2020. Daily measurements of NO${}_2$ column concentrations from the Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite were analyzed and decreases of 42% and 49.6% were found for SP and RJ, respectively, during the year 2020 compared to the 2015–2019 average. Besides NO${}_2$ column retrievals, ground-based data measured by the Brazilian States Environmental Institutions were analyzed and correlated with satellite retrievals. Correlation coefficients between year-to-year changes in satellite column and ground-based concentrations were 77% and 53% in SP and RJ, respectively. Ground-based data showed 13.3% and 18.8% decrease in NO${}_2$ levels for SP and RJ, respectively, in 2020 compared to 2019. In SP, no significant change in PM${}_{2.5}$ was observed in 2020 compared to 2019. To further isolate the effect of emissions reduction due to the lockdown, meteorological data and number of wildfire hotspots were analyzed. NO${}_2$ concentrations showed negative and positive correlations with wind speed and temperature, respectively. PM${}_{2.5}$ concentration distributions suggested an influence by the wildfires in the southeast region of the country. Synergistic analyses of satellite retrievals, surface level concentrations, and weather data provide a more complete picture of changes to pollutant levels.

中文翻译：

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COVID-19锁定期间巴西东南部的空气质量：组合的卫星和地面数据分析

随着当前COVID-19大流行在全球范围内蔓延，正在实施封锁措施，使一些国家的空气污染水平下降。在这种情况下，结合了卫星和地面每日数据分析，解决了人口稠密和人口贩运的巴西圣保罗（SP）和里约热内卢（RJ）州的空气质量变化。我们探索了二氧化氮（否${}_{\mathrm{2个}}$）和细颗粒物（PM${}_{2.5}$）2015-2020年5月份的每日水平。每日NO的测量${}_{\mathrm{2个}}$分析了NASA的Aura卫星上的臭氧监测仪（OMI）的柱浓度，与2015-2019年的平均值相比，2020年SP和RJ的浓度分别降低了42％和49.6％。除了没有${}_{\mathrm{2个}}$列检索，分析了巴西国家环境机构测量的地面数据，并将其与卫星检索相关联。SP和RJ中卫星列的年变化与地面浓度之间的相关系数分别为77％和53％。地面数据显示NO减少了13.3％和18.8％${}_{\mathrm{2个}}$ 与2019年相比，SP和RJ的水平分别为2020年。${}_{2.5}$2020年的观测值与2019年的观测值进行了比较。为了进一步隔离由于封锁而导致的减排量的影响，分析了气象数据和野火热点的数量。不${}_{\mathrm{2个}}$浓度分别与风速和温度呈负相关和正相关。下午${}_{2.5}$浓度分布表明该国东南部地区野火的影响。通过对卫星取回，地表浓度和天气数据的协同分析，可以更全面地了解污染物水平的变化。