Surface and satellite observations of air pollution in India during COVID-19 lockdown: Implication to air quality.

The strict nationwide lockdown imposed in India starting from 25 March 2020 to prevent the spread of COVID-19 disease reduced the mobility and interrupted several important anthropogenic emission sources thereby creating a temporary air quality improvement. This study conducts a multi-scale (national-regional-city), multi-species, and multi-platform analysis of air pollutants and meteorological data by synergizing surface and satellite observations. Our analysis suggests a significant reduction in surface measurements of nitrogen dioxide (NO) (46-61 %) and fine particulate matter (PM) (42-60 %) during the lockdown period that are also corroborated by the reduction in satellite observed aerosol optical depth (AOD) (3-56 %) and tropospheric NO column density (25-50 %) data over multiple cities.