psychrometric_vapor_pressure_wet

metpy.calc.psychrometric_vapor_pressure_wet(dry_bulb_temperature, wet_bulb_temperature, pressure, psychrometer_coefficient=<Quantity(0.000621, '1 / kelvin')>)[source]

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

This uses a psychrometric relationship as outlined in [WMO8-2014], with coefficients from [Fan1987].

Parameters:
  • dry_bulb_temperature (pint.Quantity) – Dry bulb temperature
  • wet_bulb_temperature (pint.Quantity) – Wet bulb temperature
  • pressure (pint.Quantity) – Total atmospheric pressure
  • psychrometer_coefficient (pint.Quantity, optional) – Psychrometer coefficient. Defaults to 6.21e-4 K^-1.
Returns:

pint.Quantity – Vapor pressure

Notes

e=ew(Tw)Ap(TTw)
  • e is vapor pressure
  • ew(Tw) is the saturation vapor pressure with respect to water at temperature Tw
  • p is the pressure of the wet bulb
  • T is the temperature of the dry bulb
  • Tw 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.