Special Operations Forces Medical Handbook

A-40

Wet Bulb Globe Temperature (WBGT)

Microclimates:
The WBGT reflects the effects of radiant (sun) energy and the effects of evaporation on effective temperatures.
It should be noted that anything that changes these factors changes the WBGT. Standing in the shade on a
sunny day is cooler, and being below the crest of a hill, protected from the breeze eliminates the cooling effects
of the wind, so it is warmer. Being in a narrow valley by a stream (humid) will be hotter then a WBGT taken in a
clearing. Local differences can be extremely important. Do not generalize from a single WBGT.

2 ft. 2 ft.

4

ft.

12-14" x 8", light wood

frame and cover with

thermal screen, coolshade

or equivalent or use std

weather enclosure.

Plywood top

Thermometer

Bottom to

be open

Suspend by wire or

string/Support

thermometer by hook

or string

Wick

3/4" Flask

Thermometer

suspended by wire

or string

3/8-5/8 in brass tube

soldered onto sphere

6" diameter

metal sphere

painted flat

black

Rubber

stopper

GROUND

Wet Bulb

Shaded Dry

Bulb

Globe