Global and regional variations in aerosol loading during COVID-19 imposed lockdown

In the backdrop of upward trend in anthropogenic aerosols over global hotspot regions, the air quality had improved worldwide post declaration of the Corona virus disease-2019 (COVID-19) as a global pandemic in mid March-2020. Present study using Moderate Resolution Imaging Spectroradiometer (MODIS) satellite derived aerosol optical depth (AOD) and the Modern-Era Retrospective analysis for Research and Applications (MERRA) version-2 datasets however, demonstrates the regional variation in aerosol loading during peak of the lockdown period. Reduction in aerosol loading over majority of the aerosol hotspots is observed from mid-March/April2020 with highest percentage reduction in the month of May. Reduction in aerosol loading over global hot spots resulted in positive surface aerosol radiative forcing (ARF, up to 6 Wm(-2)). Albeit reduction in aerosol loading observed worldwide, the considerable above normal aerosol burden was identified during April-May 2020 over the Amazon river basin, northern parts of the South America, Mexico region, South-West parts of the Africa and South East Asian region. Analysis revealed that the wildfire emission contributed significantly in anomalous aerosol burden over these regions during the lockdown period. An appropriate mitigation measures to reduce wildfire emissions is essential in addition to controlled anthropogenic emissions as far as air quality, deforestation and ecosystem is concerned.

Automated summary

The study shows that during the COVID-19 pandemic lockdown, there was a reduction in aerosol loading over most global hotspots, with some regions like the Amazon, northern South America, Mexico, South-West Africa, and South East Asia experiencing abnormally high aerosol burdens due to wildfire emissions.