psychrometric_vapor_pressure_wet#
- metpy.calc.psychrometric_vapor_pressure_wet(pressure, dry_bulb_temperature, wet_bulb_temperature, psychrometer_coefficient=None)[source]#
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:
pressure (
pint.Quantity
) – Total atmospheric pressuredry_bulb_temperature (
pint.Quantity
) – Dry bulb temperaturewet_bulb_temperature (
pint.Quantity
) – Wet bulb temperaturepsychrometer_coefficient (
pint.Quantity
, optional) – Psychrometer coefficient. Defaults to 6.21e-4 K^-1.
- Returns:
pint.Quantity
– Vapor pressure
Examples
>>> from metpy.calc import psychrometric_vapor_pressure_wet, saturation_vapor_pressure >>> from metpy.units import units >>> vp = psychrometric_vapor_pressure_wet(958 * units.hPa, 25 * units.degC, ... 12 * units.degC) >>> print(f'Vapor Pressure: {vp:.2f}') Vapor Pressure: 628.15 pascal >>> rh = (vp / saturation_vapor_pressure(25 * units.degC)).to('percent') >>> print(f'RH: {rh:.2f}') RH: 19.83 percent
See also
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)