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

Objectives: To provide novel quantification and advanced measurements of surface temperatures (T_s) in playgrounds, employing multiple scales of data, and provide insight into hot-hazard mitigation techniques and designs for improved environmental and public health. Methods: We conduct an analysis of T_s in two Metro-Phoenix playgrounds at three scales: neighborhood (1km resolution), microscale (6.8m resolution), and touch-scale (1cm resolution). Data were derived from two sources: airborne remote sensing (neighborhood and microscale) and in situ (playground site) infrared T_s (touch-scale). Metrics of surface-to-air temperature deltas (δT_s-a) and scale offsets (errors) are introduced. Results: Select in situ T_s in direct sunlight are shown to approach or surpass values likely to result in burns to children at touch-scales much finer than T_s resolved by airborne remote sensing. Scale offsets based on neighbourhood and microscale ground observations are 3.8C and 7.3C less than the δT_s-a at the 1cm touch-scale, respectively, and 6.6C and 10.1C lower than touch-scale playground equipment T_s, respectively. Hence, the coarser scales underestimate high T_s within playgrounds. Both natural (tree) and artificial (shade sail) shade types are associated with significant reductions in T_s. Conclusions: A scale mismatch exists based on differing methods of urban T_s 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 T_s 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.