Weerwoord | Uit: Atmospheric Science Wallace & Hobbs

"Wet bulb temperature is measured with a thermometer covered with a damp cloth over which ambient air is drawn. The heat required to evaporate the water from the cloth to saturate the ambient air is supplied by the air as it comes in contact with the cloth. When the difference in temperatures of the bulb and the ambient air is steady and sufficient to supply the heat needded to evaporate the water, the thermometer will read a steady temperature; which is called the wet bulb temperature."

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"The definition of wet-bulb temperature and dew point both involve cooling a hypothetical air parcel to saturation, but there is a distinct difference. If the saturated air approaching the wet bulb has a mixing ratio w, the dew point Td is the temperature to which the air must be cooled at constant pressure to become saturated. The air that leaves the wet bulb has a mixing ratio w' that saturates it at temperature Tw. If the air approaching the web bulb is unsaturated, w'is greater than w; therefore, Td < Tw < T (eigenlijk tekentje is groter dan/gelijk aan, maar die herkent ww niet), where the equality signs apply only to air saturated with respect to a plane surface of pure water. Usually, Tw is close to the arithmetic mean of T and Td."