343 Analysis of a wet bulb globe temperature algorithm at White Sands Missile Range for use with a heat stress index

Monday, 24 January 2011
Washington State Convention Center
Ryan M. LaQuay, Dryden Flight Research Center, Edwards, CA


In locations where workforce is exposed to high relative humidity and light winds, heat stress is a significant concern. Such is the case at the White Sands Missile Range in New Mexico. Heat stress is depicted by the wet bulb globe temperature, which is the official measurement used by the American Conference of Governmental Industrial Hygienists. The wet bulb globe temperature is measured by an instrument which was designed to be portable and needing routine maintenance. As an alternative form for measuring the wet bulb globe temperature, algorithms have been created to calculate the wet bulb globe temperature from basic meteorological observations. The algorithms are location dependent; therefore a specific algorithm is usually not suitable for multiple locations. Due to climatology similarities, the algorithm developed for use at the Dryden Flight Research Center was applied to data from the White Sands Missile Range. A study was performed that compared a wet bulb globe instrument to data from two Surface Atmospheric Measurement Systems that was applied to the Dryden wet bulb globe temperature algorithm. The period of study was from June to September of 2009, with focus being applied from 0900 to 1800, local time. Analysis showed that the algorithm worked well, with a few exceptions. The algorithm becomes less accurate to the measurement when the relative humidity is over 35% or the dew point temperature is over 10° Celsius. Cloud cover also plays a significant role on the measured wet bulb globe temperature by blocking radiation. The algorithm does not show red and black heat stress flags well due to the generally shorter time scales of the events. The results of this study show that it is plausible that the Dryden Flight Research wet bulb globe temperature algorithm is compatible with the White Sands Missile Range, except for when there are increased dew point temperatures and cloud cover. During such occasions, the wet bulb globe temperature instrument would be the preferred method of measurement. The amount of accuracy used for this study was actually greater than the generally accepted accuracy for wet bulb globe temperature measurement, and twenty-three out of thirty examined days fell within the good accuracy range.

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