Recent advances in satellite mapping of global air quality: evidences during COVID-19 pandemic

There was a significant decline in air pollution in different parts of the world due to enforcement of lockdown by many countries to check the spread of the coronavirus (COVID-19) pandemic. In particular, commercial and industrial activities had been limited globally with restricted air and surface traffic movements in response to social distancing and isolation. Both satellite remote sensing and ground-based monitoring were used to measure the change in the air quality. There was momentous decline in the averaged concentrations of nitrogen dioxide (NO₂), carbon dioxide (CO₂), sulphur dioxide (SO₂), methane (CH₄) and aerosols. Many cities across India, China and several major cities in Europe observed strong reductions in nitrogen dioxide levels dropping by around 40-50% owing to lockdowns. Similarly, concentrations of SO₂ in polluted areas in India, especially around large coal-fired power plants and industrial areas decreased by around 40% as evidenced by the comparative satellite mapping during April 2019 and April 2020. Recent advances in sensors on board various satellites played a significant role in real-time monitoring of emission regimes over various parts of the world. The satellite data is relying upon single scene profusion for real-time air quality measurements, and also using averaged dataset over certain time-period. The daily global-scale remote sensing data of NO₂, as measured through the Copernicus Sentinel-5 Precursor Tropospheric Monitoring Instrument (S5p/TROPOMI) of European Space Agency (ESA), indicated exceptional decreases in tropospheric NO₂ pollution in urban areas. Similarly, Greenhouse gases Observing Satellite (GOSAT) of Japan Aerospace Exploration Agency, with a repeat cycle of three days helped in assessing the sources and sinks of CO₂ and CH₄ on a sub-continental scale.

The online version contains supplementary material available at 10.1007/s42398-021-00166-w.