EGU21-8677, updated on 27 Dec 2023
EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Classification and transformation of aerosols over selected Indian cities during reduced emissions under COVID-19 lockdown

Pradeep Attri1, Siddhartha Sarkar2, and Devleena Mani1
Pradeep Attri et al.
  • 1Centre for Earth Ocean and Atmospheric Sciences, University of Hyderabad, India (,
  • 2Geosciences Division, Physical Research Laboratory, Ahmedabad, India (

An improved air quality around the globe and over India has been witnessed during the Covid-19 pandemic lockdown. Using surface observations of particulate matter and chemical species data and products from the MERRA-2 reanalysis Ångstrom exponent (α) and aerosol optical depth (AOD), this study documents the changes in atmospheric chemistry over the Indian subcontinent as a result of nationwide lockdown. Two major cities are selected in five Indian regions to cover a large spatial domain. A general shift from fine to coarse particle size, predominantly of dust type, in all regions is observed, which implies a lowered residence time of aerosol in the atmosphere during decreased anthropogenic emissions. For the studied period, Thiruvananthapuram is the cleanest city with marine origin aerosols and an average PM2.5 concentration of 7.69±2.40µg/m3 in the last phase of nationwide lockdown. Over Delhi and Ahmedabad, industrial and vehicular emission play important role in influencing the air quality. The diurnal variation of O3 and NO2 and their interdependency on each other vary over space and time, with the sharp nighttime O3 peak observed in the southern region for each lockdown phase. Biomass burning type aerosols decrease over the eastern region. In lockdown, NO2 also shows a significant correlation with population density (R2 = 0.75; p < 0.05), suggesting human mobility (and accordingly vehicular emissions) as the major contributor to NO2 concentration in the atmosphere. The results of present study did not find any relationship between the ambient concentrations of pollutants to the cumulative increase in COVID-19 cases. However, there is a significant relationship with O3 concentrations, and in turn with NO2, which can be associated with respiratory ailments.

How to cite: Attri, P., Sarkar, S., and Mani, D.: Classification and transformation of aerosols over selected Indian cities during reduced emissions under COVID-19 lockdown, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8677,, 2021.

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