Improvements in Estimating Wet Bulb Globe Temperature Using Full-Scale Measurement Platform Observations

The wet bulb globe temperature (WBGT) is being increasingly applied as a heat stress metric, particularly by workplaces and activities associations. Accurate measurements or estimations of WBGT are key in making appropriate heat safety-related decisions. Many studies have examined the estimation of WBGT and its components using standard meteorological variables (e.g., temperature, humidity, wind speed, and solar radiation). However, these studies have used sets of measured data that are limited in time and/or geographic scope. To fill this data dearth, the Range Commanders Council Meteorology Group (RCC-MG) conducted a campaign in 2021 to measure WBGT-related variables at several different climatic regions across the United States over several months using full-scale platforms with sensors compliant with International Organization for Standardization (ISO) 7243 specifications. This presentation will cover comparisons of these observed data with algorithms most frequently used for estimating black globe temperature, natural wet-bulb temperature, and the resultant WBGT. Given the comparison results and further analysis of the measured data, algorithms were developed that can be applied to any location and provide improved estimations over other methods. The improved black globe temperature estimation is based on the Dimiceli et al. (2011) model using convective heat transfer coefficients better aligned with values derived from the measured black globe temperature. Guided by algorithms from Liljegren et al. (2008) and Hunter and Minyard (1999), improvements in natural wet bulb temperature estimation were achieved using a regression equation containing solar radiation, wet-bulb depression, and wind speed. The presentation will conclude with a call for WBGT estimations from mesonet networks with requisite temperature, humidity, wind, and solar radiation observations. These estimates would be valued by data users involved in heat-related decision support services and give greater visibility to this heat stress metric.