High-Resolution Insights into Nighttime Urban Heat Island Detection: a comparative temporal analysis of 1988 and 2015 in Greater Cairo

Urban climate studies often overlook the study of nighttime urban heat island (UHI) at high spatial resolutions, such as those provided by Landsat. Previous research has primarily focused on daytime and nighttime UHI at coarser spatial resolutions, such as those offered by MODIS. Furthermore, there is a lack of studies that compare two Landsat night images over a period to assess temporal changes, which has not been comprehensively explored. In this study, the Global Artificial Impervious Area dataset was utilized to define urban, while Landsat-5 & 8 daytime and nighttime data (1988, 2015) were employed to classify land cover and extract nighttime land surface temperature (LST). Statistically significant hotspot analysis was applied to quantify the UHI. The findings revealed a 94% increase in urban cover and a 1.8% decrease in vegetation cover between 1988 and 2015. This urban expansion contributed to an average increase of 10 degrees C in LST across Greater Cairo. The analysis further indicated that every 42.7 km2 increase in urban cover corresponds to a 1 degrees C rise in LST. Streets and industrial areas exhibited the highest LST readings, while compact buildings, especially older structures, recorded higher surface LSTs compared to open buildings with diverse architectural designs, which experienced lower LST values. Hotspot analysis identified an increase in UHI intensity, with a rise from 2.5 degrees C in 1988 to 2.7 degrees C in 2015. These findings highlight the critical need for sustainable urban planning and climate-responsive policies to mitigate the adverse effects of urbanization on thermal environments. This study provides a foundation for future research and emphasizes the importance of using high-resolution nighttime thermal imagery for UHI assessments in cities worldwide.