A study published in the journal PLOS Climate examines the effectiveness of using land surface temperatures (LSTs) to estimate surface air temperatures (SATs) in subtropical, seasonally wet regions. Researchers from the University of Miami found that LST data may not accurately capture the full extent of outdoor heat exposure, particularly during the wet season, raising questions about its use in urban heat adaptation strategies. Land surface temperature and surface air temperature can vary significantly in subtropical climates.
LST-SAT Relationship with Seasonal Variations
The research, based in Miami-Dade County, Florida, employed satellite remote sensing to examine how LST and is linked to human heat exposure. To quantify air temperature, the authors used LST data as a proxy of SAT, and compared it with local weather station observations.
Their results indicated considerable seasonal differences in the relationship between LST and SAT, emphasising the complexity of using LST data in subtropical, wet areas. Although LST did map the spatial distribution of heat across the county, resulting from a surface urban heat island (SUHI) effect, the relationship between LST and SAT was largely lost during wetter spring months and absent in summer, according to the study.
Limitations of Using LST Data
Results from the study suggest that LST may underestimate residents’ heat exposure during the wet season. The time of day at which LST data are collected (around 11 AM ET/12 PM EST) could also be a factor, as this represents only one snapshot in the diurnal cycle and may not be capturing afternoon heating (especially during humid, rainy months).
“Given the increasing size and vulnerability of urban populations to heat-related health risks, these results provide a cautionary tale when considering that LST is often used as the go-to metric for informing urban heat adaptation strategies, particularly in climates that do not follow temperate patterns,” said Amy Clement, professor of atmospheric science at Rosenstiel and co-author of the study. “Given that urban heat exposure is an expanding global health risk, particularly in subtropical and tropical climates where many cities are located such as Sao Paulo, our findings underscore the importance of better tools for assessments of heat risks and responses.”
Urban Heat Adaptation Implications
The results of the study provide direct relevance for urban planners and policy-makers developing heat adaptation strategies in subtropical and tropical regions. Miami-Dade County remains at the forefront of heat policy and recent history certainly bears that out, with voters approving the very program proposal we analyzed today as well as a first-ever “Heat Season Plan” released by the City of Miami.
The authors caution that using LST as the sole metric could mislead policymakers about the risk of heat, especially during the wet season when air temperatures can be much higher than those at surfaces. Relying solely on LST data to locate heat-vulnerable neighborhoods could underestimate the severity of local temperatures, and thus miss areas where elevated temperature represents relatively new phenomena that are exacerbated into worsening heat sync trends in available space in the middle of summer and utilize adaptation protections designed elsewhere to address an issue best addressed by another causeregion. This line of investigation can be extended in future research to study the impact of local processes on the surface energy balance and ultimately its implication for LST observations in a broad spectrum of urban environments so as to get more accurate estimations of heat exposure based on LST.
