Temporal variations of urban heat islands during COVID-19 lockdown in Prague, Czechia

The Urban Heat Island (UHI) effect has significant implications for human thermal comfort, urban ecosystems, and energy consumption. The COVID-19 global lockdown presented a unique opportunity to explore the impact of reduced air pollution emissions and Anthropogenic Heat Flux (AHF) on UHI. While some studies have proposed that the lockdown’s reduction in AHF led to a decrease in both Atmospheric UHI (AUHI) and Surface UHI (SUHI), these findings are susceptible to inherent uncertainties due to unaccounted weather variability and urban-rural dynamics.

Our research provides a comprehensive analysis of the lockdown’s impact on AUHI and SUHI in Prague, Czechia. We selected days with similar weather conditions and compared the mean SUHI using MODIS satellite imagery and AUHI based on air temperature data from Prague weather stations during the lockdown period from March to April 2020 with a reference period spanning March to April 2017-2019.

Our findings reveal that the lockdown period, compared to the reference period, was associated with a 15% (0.1 °C) reduction in SUHI in Prague’s urbanized areas and a 0.7 °C decrease in AUHI in the city center. Furthermore, we observed a 12% and 29% decrease in satellite-based aerosol optical depth and nitrogen dioxide, respectively. These observations support our hypothesis that the observed weakening of UHI effects is linked to the reduction in anthropogenic activities during the lockdown. In addition, our study shows the largest decrease in mean SUHI magnitude was in the periphery, an area characterized by predominantly rural land cover. This highlights the importance of considering urban-rural dynamics when attributing changes in SUHI to AHF.

In conclusion, our study provides additional insights into the role of reduced anthropogenic activities in UHI dynamics during the COVID-19 lockdown. It offers policymakers a comprehensive understanding of how the complex interplay between urban and rural microclimate dynamics influences the SUHI phenomenon.