2.4 a Comparison of Biometeorological Comfort Indices and Human Mortality during Heat Waves in the United States

Numerous biometeorological indices have been developed to account for the thermal stresses encountered by the human body in varying ambient environments. The models from which these indices have been devised are often based on fundamental physics and incorporate factors such as the fluxes of heat and moisture from bare skin, the influence of clothing on these fluxes, and the impacts of radiant absorption and metabolism. The resulting indices provide some measure of the relative level of comfort experienced by a modeled human body in a given environment. Examples include Physiological Equivalent Temperature, Perceived Temperature, and Predicted Mean Vote. Other measures, not designed specifically for the purposes of examining human biometeorology, have also been widely applied in human comfort studies. One current popular example is the Spatial Synoptic Classification (SSC) (Sheridan 2002), an airmass-like categorical classification that serves as the basis of heat and human health watch/warning systems in implementation worldwide (Kalkstein et al. 1997). To date, no study has compared the relative efficacy of these measures in identifying heat wave deaths. In this paper, we examine seven different well-known indices that are commonly-used in human comfort studies with respect to summer heat-wave mortality in four major U.S. cities.