Impact of COVID-19 on spatio-temporal variation of aerosols and air pollutants concentration over India derived from MODIS, OMI and AIRS

The atmospheric aerosols and air pollutants affect the earth's atmosphere, human health and climate system. Human-induced aerosols and air pollutants are the major causes of the deterioration of air quality. The COVID-19 lockdown restricted the movement of people and vehicles, stopped industrial and agricultural activities and may have impacts on the aerosols in the atmosphere. Spatio-temporal map of MODIS Terra AOD_550 nm, OMI Aura UVAI, Ozone, NO(2), SO(2) and AIRS CO during the lockdown illustrates the significant reduction in their concentration. During the lockdown, the North India shows a record reduction of over 20% in Aerosol Optical Depth and Aerosol Index values. A substantial decrease in AOD and AI was also observed in Eastern and Western parts of India. The average AOD value were reduced from 1.36 (2016–2019) to 1.09 (2020) over India during the lockdown. The satellite-retrieved aerosol variables over India recorded lowest AOD values on 29th March, 2020 (0.2566) and 21st April 2020 (0.2591). Similarly, air pollutants CO, NO2 and SO2 also significantly reduced in India. Despite all variables showing a reduction in concentration, Ozone recorded an increase in value during lockdown primarily over North and North-eastern parts of India. Western India recorded a substantial reduction in SO(2) (47%) followed by Central India (31%). As pan India is considered, CO was reduced by 1%, NO(2) reduced by 15.29% and SO(2) was reduced by 26.82% during the lockdown period. This abrupt reduction in aerosol and air pollutants concentration over India was mainly due to the lockdown of COVID-19.