Relative Humidity from Wet-Bulb

In the above equation, T is the temperature in °C, Wb is the wet-bulb temperature in °C, P_sta is the station pressure in millibars, e_s is the saturation vapor pressure in millibars, e_w is vapor pressure related to the wet-bulb temperature in millibars, e is the actual vapor pressure in millibars, and rh is the relative humidity in percent.