Hot playgrounds and children's health: A multiscale analysis of surface temperatures in Arizona, USA

• A mismatch exists between remotely sensed and in situ urban surface temperatures (Ts).
• The hottest Ts in a Phoenix area neighborhood were found on playground surfaces.
• Children are more vulnerable to the effects of heat stress and high Ts than adults.
• Shade of any type is found effective in reducing Ts and improving thermal safety.
• Data must be collected at the touch-scale for spatially accurate high Ts mitigation.

ObjectivesTo provide novel quantification and advanced measurements of surface temperatures (Ts) in playgrounds, employing multiple scales of data, and provide insight into hot-hazard mitigation techniques and designs for improved environmental and public health.MethodsWe conduct an analysis of Ts in two Metro-Phoenix playgrounds at three scales: neighborhood (1 km resolution), microscale (6.8 m resolution), and touch-scale (1 cm resolution). Data were derived from two sources: airborne remote sensing (neighborhood and microscale) and in situ (playground site) infrared Ts (touch-scale). Metrics of surface-to-air temperature deltas (ΔTs–a) and scale offsets (errors) are introduced.ResultsSelect in situ Ts in direct sunlight are shown to approach or surpass values likely to result in burns to children at touch-scales much finer than Ts resolved by airborne remote sensing. Scale offsets based on neighbourhood and microscale ground observations are 3.8 ̊C and 7.3 ̊C less than the ΔTs–a at the 1 cm touch-scale, respectively, and 6.6 ̊C and 10.1 ̊C lower than touch-scale playground equipment Ts, respectively. Hence, the coarser scales underestimate high Ts within playgrounds. Both natural (tree) and artificial (shade sail) shade types are associated with significant reductions in Ts.ConclusionsA scale mismatch exists based on differing methods of urban Ts measurement. The sub-meter touch-scale is the spatial scale at which data must be collected and policies of urban landscape design and health must be executed in order to mitigate high Ts in high-contact environments such as playgrounds. Shade implementation is the most promising mitigation technique to reduce child burns, increase park usability, and mitigate urban heating.