Evaluation of the environmental stress index (ESI) for different terrestrial elevations below and above sea level

The purpose of this study was to evaluate the recently developed environmental stress index (ESI) for different climatic conditions and terrestrial elevations below and above sea level and to evaluate a new and relatively small (5 mm) infra-red (IR) light sensor for reliability and for measuring global radiation (GR). Meteorological measurements were taken in 3 different climatic zones (hot/wet, hot/dry and extremely hot/dry) at 6 different terrestrial elevations (-386, -200, 35, 375, 960 and 1640 m) for 9 days between 09:00 and 17:00. Meteorological data included ambient temperature, relative humidity, wet bulb temperature, black globe temperature and GR from two instruments: an IR light sensor and a pyranometer. In general, ESI successfully evaluated the impact of climate from the various locations at different terrestrial elevations. Global radiation measurements revealed no significant (P<0.05) differences between measurements by the pyranometer or the IR light sensor. High correlation was found between ESI and the wet bulb globe temperature index when GR was calculated from both the pyranometer (R2=0.933) and the light sensor (R2=0.939). In conclusion, ESI is a valid measure for different terrestrial elevations, and the IR sensors have the potential to measure GR for use in heat stress assessment incorporated in the index.