[AhmedEzatAlzawalaty]

i wanna know why the wet bulb temperature is lower than the dry bulb temperature? although the two thermomoeters are in the same environment and temperature of water is the same as temperature of the surrounding environment (air in which the dry bulb thermometer is )
thanx.

[nj_bartel]

I'm not completely sure what you're asking, but I think the answer is due to heat of vaporization.

[eugenedakin]

Hi AhmedEzatAlzawlaty,

nj_bartel is quite right. The dry bulb temperature measures the ambiant temperature (irrespective of humidity), while the wet bulb measures the difference in temperature due to the change in humidity (heat of vaporization).

If the humidity on the bulb (raining) is the same as the ambient air, no water vaporizes = high humidity = no temperature change. If the place is dry (desert), almost all of the water will vaporize off of the bulb and lower the temperature.

Thanks for your help nj_bartel!

Sincerely,

Eugene