Evaluation and refinement of the environmental stress index for different climatic conditions

The purpose of this study was to evaluate the recently constructed environmental stress index (ESI) for a large database comprising various climatic conditions. Data analysis of measurements from 19 locations revealed a high correlation between ESI and the wet bulb globe temperature (WBGT) index for each database. Validity from statistical analysis, including optimization procedures, slightly changed the ESI constants as follows: ESI = 0.62T_a-0.007RH+0.002SR+0.0043(T_aRH)-0.078(0.1+SR)^-1where: T_a= ambient temperature (°C); RH = relative humidity (%); and SR=solar radiation (w-m^-2). The refined ESI and the WBGT index were applied to databases of more than 125,000 measurements for each variable: T_a, RH, SR, black globe temperature (T_g), and wet bulb temperature (T_w). For each database, the ESI was then successfully correlated with the WBGT (P< 0.05, R²> 0.899). We conclude that the refined ESI, which is constructed from fast response and commonly used weather sensors (T_a, RH, SR), is a potential index to serve as an alternative to the WBGT for heat category assessment.