Urban Wind Corridor Identification and Verification of Thermal Comfort Enhancement in Urban Area

In the context of climate change and extreme weather, urban heat island (UHI) phenomenon is exacerbated, affecting people's quality of life and environmental comfort. In the hot and humid climate of Asia, urban ventilation and heat dissipation play a crucial role in improving the thermal environment and reducing heat-related risks. Previous studies have mostly focused on urban wind corridor planning, lacking sufficient evidence of the ventilation benefits of such corridors. This study aims to fill this gap by using Tainan City as a case study to demonstrate the ventilation benefits of urban wind corridors through corridor identification and long-term measurements.

Utilizing the 2-kilometer resolution historical climate reconstruction grid data (TReAD) built by the Taiwan Climate Change Projection and Information Platform (TCCIP) of the National Science and Technology Center for Disaster Reduction (NCDR), the heat island phenomenon in Tainan City is examined, and prevailing wind directions are summarized. Geographic information software is employed to calculate the roughness length and formulate urban wind corridors. Mobile observations are conducted to select and evaluate measurement points for assessing the ventilation efficiency of the corridors, followed by long-term observations to obtain high-density data and confirm the ventilation benefits of urban wind corridors.

The analysis of corridor formulation and observation yields the following research findings (1) Large open spaces in urban areas significantly increase wind speeds. For instance, at the elementary school near Tainan Park, the hourly average wind speed reaches 1.8 m/s compared to a decrease of 0.9 m/s at points without nearby open spaces, such as roads with a width of 23 meters on both sides. (2) The alignment of road traffic direction with wind direction is the primary factor affecting ventilation efficiency, followed by road width. For example, on Road A with a width of 3 meters and aligned with the wind direction, the hourly average wind speed is 0.7 m/s, compared to an increase of 0.4 m/s at Road B with a width of 21 meters but misaligned with the wind direction. (3) Wind speeds are more stable in crossroad areas. For instance, at the intersection of two road, where dual-directional ventilation occurs, the hourly average wind speed is 0.9 m/s, falling between the efficiency levels of a second-level corridor (1.2 m/s) and a third-level corridor (0.8 m/s).The results of this study can serve as a basis for future urban wind corridor planning, effectively guiding the implementation of strategies to cool urban areas and mitigate the urban heat island effect.