AUTHOR=Bhawar Rohini L. , Fadnavis Suvarna , Kumar Vinay , Rahul P. R. C. , Sinha Tushar , Lolli Simone 

TITLE=Radiative Impacts of Aerosols During COVID-19 Lockdown Period Over the Indian Region

JOURNAL=Frontiers in Environmental Science

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/environmental-science/articles/10.3389/fenvs.2021.746090

DOI=10.3389/fenvs.2021.746090

ISSN=2296-665X

ABSTRACT=The covid-19 lockdown restrictions influenced the global atmospheric aerosols. We report aerosol variations over India using multiple remote sensing datasets (Moderate Resolution Imaging Spectroradiometer (MODIS), Ozone Monitoring Instrument (OMI), Cloud-Aerosol Lidar, and Infrared Pathfinder (CALIPSO)) and model reanalysis (Copernicus Atmosphere Monitoring Service (CAMS)) during the lockdown implemented during COVID-19 pandemic outbreak period during the 25th March to 14th April 2020. Our analysis shows that, during this period, MODIS and CALIPSO show a 30-40% reduction in aerosol optical depth (AOD) over the Indo-Gangetic Plain (IGP) with respect to the decadal climatology (2010-2019). The absorbing aerosol index and dust optical depth measurements also show notable reduction over the Indian region, highlighting less emission of anthropogenic dust and also a reduced dust transport from West Asia during the lockdown period. 

On the contrary, central India showed an ~12% AOD enhancement. CALIPSO measurements reveal that this increase is due to transported biomass burning aerosols. Analysis of MODIS fire data product and CAMS fire fluxes (black carbon, SO2, organic carbon, and nitrates) show intense fire activity all over India but densely clustered over central India. Thus, we show that the lockdown restrictions implemented at the government level have significantly improved the air quality over northern India but fires offset its effects over central India. The biomass-burning aerosols formed a layer near 2-4 km (AOD 0.08 to 0.1) that produced heating 3-4 K/day and a consequent negative radiative forcing at the surface of ~ -65 W/m2 (±40 W/m2) over the central Indian region.