Land Surface Temperature Dynamics during COVID-19 Lockdown in Diverse Climatic and Physiographic Zones-A Study of Indian Mega Cities

The COVID-19 pandemic, which originated in China at the end of 2019, escalated into a global crisis by March 2020. To mitigate its spread, governments worldwide implemented strict lockdown measures. While these lockdowns had adverse social, economic, and health impacts, they also led to significant environmental improvements in many regions. India's urban environment also significantly improved during lockdown. This study investigates the changes in Land Surface Temperature (LST) across eight major Indian cities, each representing diverse climatic and physiographic zones: Delhi, Dehradun, Lucknow, Kolkata, Bhopal, Bhubaneshwar, Mumbai, and Hyderabad. It aims to enhance the understanding of how sudden reductions in anthropogenic activities influence urban temperatures. The LST was computed for the lockdown period of April to May 2020 and was compared with the pre-lockdown years of 2018 and 2019 and the post-lockdown year of 2021, utilizing Landsat thermal data processed through the mono-window algorithm. The results exhibit significant reductions in LST during the lockdown period. Cities like Delhi, Dehradun, and Lucknow experienced a reduction of 6 degrees C, 5 degrees C, and 4 degrees C, respectively, in LST from pre-lockdown to lockdown periods. In contrast, cities like Bhopal, Bhubaneswar, Mumbai, and Hyderabad experienced a reduction of around 2 degrees C-3 degrees C. However, the city of Kolkata showed an increase of 3 degrees C from 2019 to 2020. These results highlight the substantial influence of human activities on urban thermal environments and underline the potential benefits of reducing anthropogenic impacts to improve urban thermal well-being.