Spatio-temporal variation of aerosol loading and planetary boundary layer height before, during and after COVID-19 lockdown over the major cities in India

COVID-19 led to an unprecedented reduction in anthropogenic emissions due to the shutdown of worldwide economic and transportation activities. This study analyzed the spatial distribution of planetary boundary layer height (PBLH), aerosol optical depth (AOD), and aerosol index (AI) of 12 major Indian cities before COVID-19 (2018 and 2019), during first wave (2020) and second wave (2021) of COVID-19 lockdowns and post COVID period (2022). Aerosol loading decreased during the first wave, but significantly increased in all cities during the second wave of COVID-19, even during partial lockdown and relaxation in industrial activities. All 12 cities experienced 10–20% rise in aerosol loading during April, 40–70% during May, and 10–20% during June after 2022 lockdown released. PBLH shows a consistent seasonal variation with an increase from March to May followed by a decrease in May to July. Despite this trend, yearly increases in PBLH values persist, indicating a consistent rise compared to the previous year while maintaining the same seasonal pattern mentioned earlier. AI values rose from 2020 to 2022, indicating the presence of absorbing aerosols in the atmosphere during this period. The study aids planners, policymakers, and decision-makers in formulating strategies to mitigate the increasing aerosol concentration.