A recent study published in PLOS Climate on October 2, 2024, highlights the challenges of using land surface temperature (LST) to estimate outdoor heat exposure in subtropical, seasonally wet regions like Miami-Dade County, Florida. Conducted by scientists at the University of Miami Rosenstiel School, this research calls into question the reliability of LST data in fully capturing the extent of heat exposure in such climates, emphasizing the need for more precise measurements to inform urban heat mitigation efforts.
“LST data, derived from satellite imaging, has long been used to estimate surface air temperature (SAT)—the temperature people experience outdoors,” explains Nkosi Muse, lead author of the study and a Ph.D. candidate in Environmental Science and Policy at the Rosenstiel School. “LST plays a critical role in understanding urban heat risks, especially as cities grow hotter due to climate change and urbanization,” he adds.
However, the study found that the accuracy of LST as a proxy varies depending on geographic and climatic conditions. While extensively studied in temperate zones, the relationship between LST and SAT in subtropical regions with high summer rainfall, like Miami-Dade, is less understood.
The researchers compared Landsat 8 remote sensing data from 2013 to 2022 with air temperature data from local weather stations to evaluate when LST is a reliable proxy for SAT. The study revealed seasonal variations in the relationship between LST and SAT, particularly in Miami-Dade County.
LST effectively captured the spatial distribution of heat across the county, highlighting a surface urban heat island (SUHI) effect—where urban areas are notably hotter than surrounding rural regions. This effect peaked during the spring, with a mean SUHI intensity of 4.09°C, higher than in the summer, when it averaged 3.43°C.
Interestingly, LST readings in Miami-Dade peaked in May and June, contrary to typical patterns seen in temperate zones where July and August typically record the highest temperatures. In contrast, SAT in Miami-Dade reached its highest levels in August, underscoring a significant variation between LST and SAT depending on the season.
Despite its usefulness in identifying heat patterns, the study shows that LST has limitations in subtropical, seasonally wet regions like Miami-Dade County. During the wet season, LST may underestimate actual heat exposure, and the timing of LST data collection, typically at 11 AM ET/12 PM EST, may not capture peak heat conditions, particularly during humid months.
“These findings underscore the risks of relying solely on LST data for heat adaptation strategies, particularly in climates that do not follow temperate patterns,” notes Amy Clement, professor of Atmospheric Sciences and co-author of the study. “As subtropical and tropical cities face increasing heat risks, accurate measurements of heat exposure are crucial to inform adaptive responses,” she emphasizes.
The study’s findings have immediate implications for urban planners and policymakers in subtropical regions. As Miami-Dade County develops new heat policies and the City of Miami unveils its Heat Season Plan, these results suggest that relying on LST alone could misrepresent heat risks, especially during the wet season when air temperatures may far exceed surface temperatures.
This could result in inadequate heat adaptation strategies that fail to address the real intensity of heat exposure in certain neighborhoods. The research highlights the need for more sophisticated approaches to measuring and mitigating heat exposure, particularly as urban areas strive to protect vulnerable populations from extreme heat.
The study also opens the door for future research into how localized factors—such as vegetation, water bodies, and urban materials—affect surface energy balances and LST readings. Gaining a deeper understanding of these variables could enhance the accuracy of LST as a tool for measuring heat exposure in diverse urban environments.
As cities continue to grapple with rising temperatures, improving methods for accurately assessing and mitigating heat risks will become increasingly critical.
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