An assessment of the impact of a nation-wide lockdown on air pollution – a remote sensing perspective over India
Mahesh Pathakoti, Aarathi Muppalla, Sayan Hazra, Mahalakshmi Venkata Dangeti, Raja Shekhar, Srinivasulu Jella, Sesha Sai Venkata Rama Mullapudi, Prasad Andugulapati, Uma Vijayasundaram
Abstract
Abstract. The nation-wide lockdown imposed over India from 25th March 2020 onwards, in response to the COVID-19 pandemic, placed severe restrictions upon the industrial and transport sectors, which together form a significant chunk of anthropogenic emissions of pollutants into the atmosphere. Atmospheric concentrations of Nitrogen dioxide (NO2), carbon monoxide (CO) and aerosol optical depth (AOD) for lockdown and pre-lockdown periods were investigated with observations from Aura/OMI, Terra/MOPITT, Sentinel-5p/TROPOMI and Aqua-Terra/MODIS satellite sensors. Mean NO2 levels over India during the lockdown period showed a dip of 17 % as compared to pre-lockdown period and a decrease of 18 % against the 5-year average. Over New Delhi in particular, there was a sharp decrease of 62 % in NO2 levels as compared to 2019 and a decline by 54 % relative to the preceding 5-year period (2015–2019). Aerosol levels reduced over the country by ~ 24 % from the 5-year mean levels, with a marked reduction over the Indo-Gangetic plains region. An increase in CO levels was noticeable, probably due to its longer life-time as compared to NO2 and aerosols. This study also reports the rate of change of NO2, CO and AOD, indicating increase/decrease in pollutant emissions over the different states of India.