# psychrometric_vapor_pressure_wet¶

metpy.calc.psychrometric_vapor_pressure_wet(pressure, dry_bulb_temperature, wet_bulb_temperature, psychrometer_coefficient=None)

Calculate the vapor pressure with wet bulb and dry bulb temperatures.

This uses a psychrometric relationship as outlined in [WMO8], with coefficients from [Fan1987].

Parameters
Returns

pint.Quantity – Vapor pressure

Notes

$e' = e'_w(T_w) - A p (T - T_w)$
• $$e'$$ is vapor pressure

• $$e'_w(T_w)$$ is the saturation vapor pressure with respect to water at temperature $$T_w$$

• $$p$$ is the pressure of the wet bulb

• $$T$$ is the temperature of the dry bulb

• $$T_w$$ is the temperature of the wet bulb

• $$A$$ is the psychrometer coefficient

Psychrometer coefficient depends on the specific instrument being used and the ventilation of the instrument.

Changed in version 1.0: Changed signature from (dry_bulb_temperature, wet_bulb_temperature, pressure, psychrometer_coefficient)