Mapping heat – Why are pavements hotter than parks?
This UT FieldLab experiment falls under the theme Urban spaces and infrastructures. View all experiments related to this theme.
Introduction
Why does a city feel so much warmer than the countryside on a summer day? This phenomenon, known as the urban heat island (UHI) effect, impacts health, energy use, and liveability. In this experiment, we measure how big these differences are and how to capture them reliably.
As climate change intensifies extreme heat, UHIs amplify risks, particularly for vulnerable populations living in neighborhoods with limited green space and poor housing. Understanding UHI patterns is therefore not only a scientific challenge but also a pressing urban policy concern, as excessive heat directly affects livability, resilience, and sustainability.
Reliably measuring temperature variations and quantifying the intensity of the UHI is subject to the issue of scales and intra-city temperature variations, which are further related to the built environment of cities. Hence, the built environment lies at the core of UHI formation. Materials such as asphalt and dark roofs absorb and slowly release heat, while impermeable surfaces suppress natural cooling. Dense urban forms—narrow streets, tall buildings, limited sky view—trap heat and restrict airflow, while anthropogenic sources like traffic and air conditioning add to the burden. Conversely, lighter reflective surfaces, permeable pavements, vegetation, and water features can mitigate these effects through cooling and shading. All of these factors are intertwined together leading to hesitations in decision-making processes of initiating policies for mitigating and adapting excessive heat, this highlights the importance of enhanced resolution in both space and time in monitoring the temperature variations across the diverse built environment within cities.
What are we researching?
We want to know how temperature differences arise between paved, built-up, and green areas in the city. How much hotter is asphalt than grass? And how accurate are certain sensors compared to professional weather stations? This knowledge helps cities take targeted measures against heat stress, such as adding greenery or using smart materials.
How does it work?
We install small sensors in different urban microclimates: on pavements, between buildings, and in parks. These sensors continuously measure air temperature just above the ground. Their data is compared with high-grade meteorological stations to assess accuracy. By linking measurements to land use and building data, we gain insight into how surfaces influence temperature. The results also show whether low-cost sensors are suitable for large-scale urban monitoring.
Why is this important?
Heat stress is a growing urban problem, affecting health, energy demand, and biodiversity. By understanding microclimate differences, municipalities and designers can implement measures that make cities cooler and more liveable – from planting trees to using innovative paving materials.