ABSTRACT
Copernicus Atmosphere Monitoring Service (CAMS) data are used to evaluate the impact of the lockdown (24 March-3 May 2020) on the concentrations of surface O-3, NOx, CO, SO2, PM and BC compared to those measured during the same period in 2015-2019 over northeast India and adjoining areas. Measurements made at Dibrugarh complements the CAMS observations. The NOx, NO2, CO, SO2, BC and PM concentrations dipped appreciably over northeast India and nearby countries. Similar decrement is observed in Dibrugarh in 2020 over their reference levels. Reduction of precursor gases triggered an increase in O-3 concentration across northeast India and adjoining South Asia and at Dibrugarh. The air quality over the region improved from moderate to satisfactory levels due to the lockdown.