Effectiveness of potential strategies to mitigate surface urban heat island: A comprehensive investigation using high-resolution thermal observations from an unmanned aerial vehicle

Widespread utilization of satellite infrared observations has revealed potential urban morphology designs to mitigate surface urban heat island effect. However, studies towards holistic thermal effects of internal and external spatial attributes on built-up areas are limited. Moreover, the use of low-resolution thermal pixels for hybrid landscape components introduce uncertainty in deriving effective cooling strategies. Here, we obtained submeter-level land surface temperature (LST) maps and spatial datasets using an unmanned aerial vehicle and comprehensively evaluated impacts of urban characteristics on LST during a hot summer day. The results of a random forest model indicated that 2D landscape composition had the strongest thermal contribution at block scale. Conversely, at fine-scale impervious activity space, 3D spatial configuration governed daytime LST, and the identified crucial influencing metrics represented by sky view factor exhibited non-linear correlations with LST. Accordingly, shade casting was a core mechanism through which 3D elements collectively contributed to outdoor heat dissipation, more efficient than effects of surface materials and their optical properties. Furthermore, regarding uncertain exogenous thermal impact of large blue-green spaces, no significant cooling effects were detected on adjacent built-up surfaces. These findings provided prioritized insights on how to integrate diverse urban elements to effectively reduce outdoor heat stress.