Atmospheric pollutant levels in Southeast Brazil during COVID-19 lockdown: combined satellite and ground-based data analysis

Abstract:

With the ongoing 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 Southeast Brazil are hereby going to be addressed using a combination of satellite and ground-based daily data analysis. The aimed study areas are the highly populated and industrialized states of São Paulo and Rio de Janeiro. Initially, we explore nitrogen dioxide (NO₂) levels, but more atmospheric pollutants will be added as the study is developed. Our timeframe is the month of May in the years 2015 to 2020, with the first five years being compared to the current 2020 year. Daily measurements of NO₂ column concentrations from the Ozone Monitoring Instrument (OMI) aboard NASA's Aura satellite are averaged for the month of May. Preliminary results already show a significant decrease in NO₂ levels when the 2015-2019 satellite data average is compared to the 2020. In parallel to the NO₂ column retrieval, the ground-based data, measured by the Brazilian States Environmental Institutions, are analyzed, and the correlations between satellite and ground-based concentrations are studied. To further quantify the effect of emissions reduction due to the lockdown, the combined data is weather-normalized using local meteorological observations. This integrated approach (combined satellite and ground-based analysis) is innovative and has yet to be more explored in Brazilian studies. This is true specifically because the ground-based stations are spatially and temporally sparse in Brazil.