Cooling ranges for urban heat mitigation: continuous cooling effects along the edges of small greenspaces

This study assessed the cooling ranges of small greenspaces (SGs) along the edges of surrounding areas and identified the spatial cooling distance threshold. Five SGs in a natural preserved public area located in College Station, Texas, USA, and a reference site (Rf) were selected for this study. Air temperature data collection took six rounds from fall to early summer. In each round air temperature was collected three times during a day (i.e., 10 h, 13 h, and 16 h). Temperature sensing units (TVCs) and loggers recorded air temperature every second via a transect survey. The cooling distance was determined according to each SG’s radius: (1) the centroid of the SG (GC), (2) the edge of the SG (GE), (3) 1.25 times the radius away from the GC (1.25R), and (4) 1.5 times the radius away from the GC (1.5R). Our findings showed the SGs’ cooling effect (∆TRf−i) surpassed their edges in general. The cooling degrees at the GC were higher and dropped continuously from the GE to 1.25R ending with 1.5R showing the lowest. In fall, the SGs’ mean cooling degree exceeded 9.24% at 1.5R compared to Rf. In early summer, the SGs’ mean cooling effects decreased significantly while showing a very small difference between the measurement points. Our findings contribute to uncovering some specific design features with SGs to cooling down cities by applying advanced technology. Our findings will help designers, planners, researchers, and local government officials by providing an optimal landscape planning and design guide for mitigating urban heat.