Space-Based Observations on The Impact of COVID-19-Induced Lockdown on Aerosols over India

The lockdown period in India due to COVID-19 came into effect from 25 March 2020 onwards. The present study analyses the changes and trends in aerosol optical depth (AOD) levels during the last few months and particularly during lockdown period. MODIS observations showed an average reduction of 20–37% in aerosol loading during the lockdown period (25 March–3 May 2020), compared to 2017–2019 across India. A clear-cut and drastic reduction in AOD (which includes both PM2.5 and PM10) was observed at many places across India, in particular over North India (46%), eastern Indo-Gangetic Plains (42%) and peninsular India (30%). Maximum decrease in AOD was seen during 25 March to 5 April 2020 with values as low as 0.18–0.22, which are 72–87% lower than the February–March 2020 level. AOD then slightly increased in the third week of April due to stubble burning and a few cloudy days, and then fell subsequently. Ground measurements on air pollutants at selected Indian cities revealed reduction of 40–50% in surface concentration prior to the lockdown period. Thus, study shows a clear-cut improvement in air quality leading to significant improvement in visibility and more blue skies.