What is a wet bulb globe temperature?

  • Published
  • By Airman 1st Class Frank John Casciotta
  • 71st Flying Training Wing Public Affairs
VANCE AIR FORCE BASE, Okla. --  Nearly every day Team Vance members receive weather advisory emails from the 71st Flying Training Wing Command Post telling them that, according to the wet bulb globe temperature, it's hot outside.

The frequency of these emails might be less than desirable to some, however they do serve the purpose of keeping people informed, said Tech. Sgt. Jose Melendez-Alvarez with the 71st Medical Operations Squadron and the NCO in charge of the bioenvironmental element.

The WBGT reading comes from the combined information of three types of thermostats that measure the different elements of the environment outside, said Melendez-Alvarez.

The three thermometers combine air temperature, mean radiant temperature, air speed and absolute humidity to give a better idea of how the temperature will feel to a person.

The dry bulb temperature is measured by a thermometer that senses the temperature of the air without accounting for moisture.

The wet bulb accounts for the humidity in the air and how it might affect a person based on the evaporation rate.

The black globe measures the combined effects of solar radiation and wind, which accounts for how much heat is being generated on surfaces.

The flag system is in place to let people know how much strain the heat will put on the body and the proper precautions to take before working or exercising outside, said Melendez-Alvarez.

The flag colors are green, yellow, red and black, with black being the highest. "The higher the flag level the more likely you are to get a thermal injury," said Melendez-Alvarez.

People working or exercising outside should consult a work-rest cycle and fluid replacement chart for proper hydration and activity limits to prevent heat injuries. A work-rest cycle chart is available in Air Force Pamphlet 10-100, "Airman's Manual," on page 216. The Airman's Manual is available at http://www.e-publishing.af.mil/shared/media/epubs/AFPAM10-100.pdf.