Quantifying the average cooling effects of tree, artificial, and hybrid shade using city-wide IoT sensor measurements: A case study of Seoul

As urban heat stress continues to rise, strategies to mitigate heat for pedestrians through the provision of shade have become essential. While many studies have quantified the cooling benefits of shade and highlighted its importance for urban planning, the specific effectiveness of different shade types across various conditions remains unclear. Most previous studies have either modeled shade effects or relied on limited field measurements, leaving a research gap in evaluating the average cooling effect of shade across an entire city using real-world data. To address this gap, this study used city-scale sensor data to analyze the cooling effects of tree, artificial, and hybrid shades during heatwaves. The results indicated that all types of shade effectively reduced air temperature and Wet Bulb Globe Temperature (WBGT). Notably, hybrid shade—artificial structures complemented by adjacent trees—exhibited superior cooling performance compared to other shade types. While the average cooling effects of tree shade and artificial shade were generally similar, the cooling effect of tree shade, which was relatively weak during the morning, became stronger than that of artificial shade in the afternoon. Moreover, shade conditions characterized by high density that can maintain low lux levels consistently demonstrate greater cooling effectiveness. These insights can help explain the inconsistencies in previous findings on the effects of shade. These findings highlight the importance of incorporating shade provision into urban planning to maximize cooling benefits. Ultimately, the improved understanding of shade effects will contribute to decision-making in cooling cities to respond to future climate change.