Spatial Patterns of Nocturnal Urban Heat Island and Their Significance for Human Heat Stress Impacts

Various studies have highlighted the contributions of the urban heat island (UHI) to exacerbating health impacts during heat waves, as well as how this may change with any climatic warming. Particular concern is in cases where high moisture content near the surface combine with the UHI effect of anthropogenic heat retention to further limit the degree of nocturnal cooling in a calm poorly mixed near-surface environment. In some urban areas, there is evidence that the physical forcing for these health-impacting nocturnal UHI signatures may be disproportionately strong in neighborhoods of depressed socioeconomic conditions, due to increased population density, decreased green vegetation coverage, and surface drainage problems. In contrast to the typical approaches of multiple stationary observing sites (spatially discrete) and thermal infrared imagery (two-dimensionally continuous, but indirect), we utilize mobile observations (every 10 sec) along strategic transects through the Jackson, MS metropolitan area. Following adjustment for temporal variations during the data collection, an essentially continuous depiction of both temperature and humidity patterns (in one dimension) is obtained. These are then converted to sensible/apparent temperature indexes in order to investigate the variability of heat stress risks within the urban area.