Rapid growth and high cloud-forming potential of anthropogenic sulfate aerosol in a thermal power plant plume during COVID lockdown in India

The COVID lockdown presented an interesting opportunity to study the anthropogenic emissions from different sectors under relatively cleaner conditions in India. The complex interplays of power production, industry, and transport could be dissected due to the significantly reduced influence of the latter two emission sources. Here, based on measurements of cloud condensation nuclei (CCN) activity and chemical composition of atmospheric aerosols during the lockdown, we report an episodic event resulting from distinct meteorological conditions. This event was marked by rapid growth and high hygroscopicity of new aerosol particles formed in the SO2 plume from a large coal-fired power plant in Southern India. These sulfate-rich particles had high CCN activity and number concentration, indicating high cloud-forming potential. Examining the sensitivity of CCN properties under relatively clean conditions provides important new clues to delineate the contributions of different anthropogenic emission sectors and further to understand their perturbations of past and future climate forcing.

Automated summary

The COVID lockdown in India provided an opportunity to study anthropogenic emissions under cleaner conditions. Measurements of CCN activity and aerosol composition during the lockdown revealed an episodic event caused by meteorological conditions. This event was characterized by rapid growth and high hygroscopicity of aerosol particles from a coal-fired power plant, which had high cloud-forming potential. Studying CCN properties under cleaner conditions helps to understand the contributions of different emission sectors and their impact on climate forcing.