Pukyong National University

Pukyong National University Research Team Identifies the Urban Heat Island as a “Day-Night Thermal Asymmetry Structure”

- Published in the international journal <Nonlinear Processes in Geophysics>

Pukyong National University announced that researcher Jeon Mi-Jeong from the research team led by Professor Moon Woo-Seok of the Major in Environmental Atmospheric Sciences has recently published a study in Nonlinear Processes in Geophysics explaining the Urban Heat Island (UHI) phenomenon―where temperature differences arise between urban and surrounding suburban areas―using a simplified thermodynamic model.

The study focuses on physically explaining why and when the urban heat island becomes most intense. The Urban Heat Island refers to the phenomenon in which temperatures in urban areas are higher than those in nearby suburban regions, and it is a major climate-related issue associated with intensified heat waves, increased energy demand, and heightened health risks.

However, many previous studies have relied on listing observational cases or complex numerical models, which made it difficult to intuitively understand the core mechanisms behind the phenomenon. To address this limitation, the research team approached urban temperature variation from the perspective of the ‘Surface Energy Balance,’ proposing a simplified thermodynamic model composed of a minimal set of variables.

According to the study, cities absorb a large amount of solar radiation during the daytime, with a significant portion of that heat stored in artificial structures such as buildings, roads, and concrete surfaces. This stored heat is released slowly at night, causing urban areas to cool more slowly than surrounding regions and thereby intensifying the nighttime urban heat island effect.

The research team expressed these processes through a mathematically simplified model, illustrating how heat accumulation during the daytime and heat release during the nighttime contribute to urban temperature changes. Through this approach, the study clearly explains that the urban heat island phenomenon is not simply that “cities are hotter,” but rather that it arises from an asymmetric structure of heat that accumulates and is released over time.

Professor Moon Woo-Seok stated, “This study is meaningful in that it explains the urban heat island phenomenon not through complex large-scale climate models, but through a simple yet interpretable model that can reproduce the phenomenon using only a minimal set of variables.” He added, “Beyond conventional empirical and statistical approaches, the most significant achievement of this research is providing a fundamental understanding of how cities store and release heat.”

This approach enables a more intuitive understanding of urban climate and is expected to be useful for scientifically evaluating practical mitigation strategies, including urban design, expansion of green spaces, selection of building materials, and heatwave response policies. <Pukyong Today>