The quality of residents' lives have been negatively affected by problems resulting from global warming and urban heat island. Investigators have explored several ways to mitigate those problems. They found that vegetation (especially trees) and water surfaces played a significant role in the adjustments of climate. Sites with more vegetation and larger-size waterbodies were cooler. However, the cooling effects of these elements were affected by contextual factors. For instance, cooling intensities of both vegetation and water surfaces fluctuated through the day. To further explore this phenomenon, this study investigated the cooling effects of trees and large waterbodies at different times of the day by means of field measurement. It was found that leaf area index (LAI) and distance from the sea (DFS) had a significant impact on park cooling intensities (PCI). Park points with more trees (indicated higher LAI) and those located closer to the sea were cooler. In addition, their cooling effects varied depending on the time of the day. LAI showed significant microclimatic adjusting effects late in the evening. Increasing the LAI by 1 point could help increase the PCI by 0.31 °C (18:00, R2 = 0.2421). In contrast, rising DFS resulted in PCI decrease by more than 2 °C (12:00 p.m., R2 = 0.4327). Cooling performances of the two factors were significant at different time periods of the day, that is, in the noon (the sea) and evening (trees) respectively. Further, the cooling effects of the trees might be affected by the distance from the sea. Findings from this study provided new understandings towards the climatic conditions of waterside cities.
Keywords: Coastal cities; Distance from the sea; Leaf area index; Park cooling intensity; Parks.
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