Investigating Persistence Surface Urban Heat Island (PSUHI) with respect to the Local Climate Zones (LCZs) in Chicago, USA

Persistence Surface Urban Heat Island (PSUHI), the fraction of a season that an urban heat island (UHI) is present on the ground, is an easily observed UHI metric that can be used to map UHI zones. In this study, we map PSUHI using UHI calculated from the 'MODIS MOD11A1 1km resolution Land Surface Temperature and Emissivity' data product and investigate how PSUHI relates to the local scale landscape types using Local Climate Zones (LCZs) for the city of Chicago. Our findings indicate that high-intensity SUHIs are persistent in compact low-rise, open low-rise, and large low-rise LCZs in Chicago from 2003-2021. Trends in night-time Land Surface Temperature (LST) also confirm this with significantly increasing large patches in open and large low-rise LCZs. In contrast to common belief, this study successfully found that the highest SUHI intensities are not limited to compact high-rise, compact mid-rise, or heavy industrial areas. This study offers a framework for comparing PSUHI between different LCZs, highlights urban formations with UHI changes, and can facilitate analyses of why urban heating varies within and between LCZs. These results can serve as a valuable reference for establishing effective mitigation strategies that can accurately respond to the spatio-temporal variability of PSUHIs. They have the potential to optimize the major investments cities are making in green infrastructures, such as Chicago's $46M Tree Equity program aimed at restoring the city's tree canopy as a strategy to reduce UHI impacts on communities. Opening up the data to the public could lead to additional mitigation strategies initiated by local communities.