# Apparent temperature

This online calculator computes the apparent temperature, taking into consideration wind speed and relative air humidity. It uses the Australian Bureau of Meteorology formula

So, the calculator about Wind Chill Index can tell us how cold the wind is. But there is another important formula that can define human thermal comfort, called the 'apparent temperature' (AT). AT is a heat index invented in Australia by a researcher named Robert Steadman, whose work was published in 1984. It takes into consideration four environmental factors: wind, temperature, humidity and radiation from the sun.

The formula for the AT is:

where

Ta = Dry bulb temperature (°C)

e = Water vapour pressure (hPa) [humidity]

ws = Wind speed (m/s) at an elevation of 10 meters

Q = Net radiation absorbed per unit area of body surface (W/m2)

E is computed like this

where

rh = Relative Humidity [%]

While temperature and humidity are regional and seasonal factors, wind and radiation are microclimatic factors and are influenced by the local environment. I think that it is quite hard to measure or estimate radiation, therefore here I am not using the radiation term, thus this calculator computes apparent temperature for outdoors in the shade. Also it plots the dependency of apparent temperature on humidity.

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