Wearable sensing techniques to understand pedestrian-level outdoor microclimate affecting heat related risk in urban parks

Around the world people are rapidly moving to cities. The rapid urbanization has led to changes in land use and land cover, which (i) modify the urban surface energy balance making the cities hotter than the surrounding rural area, (ii) exacerbate the impact of extreme weather events like heatwaves and (iii) lead to poor quality of life. City administrations around the world are undertaking drastic measures to mitigate extreme heat. Here, in this study we test a wearable sensing platform to both study pedestrian-level microclimate boundary conditions as well as the impact of urban greening on moderating excess heat in dense urban areas. The experiment presented here was conducted in New York City. Typically, the urban thermal state is estimated by means of direct observations from ground-based sensors, satellite based remote sensing techniques, and high-resolution urban climate modeling, all of which are too coarse to resolve pedestrian-level impacts, a key parameter in determining heat stress for citizens occupying the outdoors. Here a wearable and a portable sensing apparata were used to monitor key environmental parameters - air temperature, relative humidity, wind speed, mean radiant temperature and solar radiation. The coupled monitoring platform included multiple sensors and a wireless data logging system which were all prototyped by the authors on open source technologies. The sensor platform was able to accurately map the thermal environment of multiple dense urban spaces, being to reproduce the spatial variability in key microclimate parameters, and the performance was comparable to traditional stationary ground-based weather stations. The results, which may be of key help also for validating microclimate forecasting models, indicate high spatial variability in temperature, humidity and solar radiation within the same urban parks. Our findings also indicate that on average small urban parks in a dense urban setting were able to reduce the air temperature by 3–7 °C in New York City with major gains during the mid-afternoon periods.