saturation_vapor_pressure#

metpy.calc.saturation_vapor_pressure(temperature, *, phase='liquid')[source]#

Calculate the saturation (equilibrium) water vapor (partial) pressure.

Parameters:

  • temperature (pint.Quantity) – Air temperature

  • phase ({'liquid', 'solid', 'auto'}) – Where applicable, adjust assumptions and constants to make calculation valid in 'liquid' water (default) or 'solid' ice regimes. 'auto' will change regime based on determination of phase boundaries, eg temperature relative to freezing.

Returns:

pint.Quantity – Saturation water vapor (partial) pressure

Examples

>>> from metpy.calc import saturation_vapor_pressure
>>> from metpy.units import units
>>> saturation_vapor_pressure(25 * units.degC, phase='liquid').to('hPa')
<Quantity(31.623456, 'hectopascal')>

See also

vapor_pressure, dewpoint

Notes

Instead of temperature, dewpoint may be used in order to calculate the actual (ambient) water vapor (partial) pressure.

Implements separate solutions from [Ambaum2020] for

phase='liquid', Eq. 13,

\[e = e_{s0} \frac{T_0}{T}^{(c_{pl} - c_{pv}) / R_v} \exp \left( \frac{L_0}{R_v T_0} - \frac{L}{R_v T} \right)\]

and phase='solid', Eq. 17,

\[e_i = e_{i0} \frac{T_0}{T}^{(c_{pi} - c_{pv}) / R_v} \exp \left( \frac{L_{s0}}{R_v T_0} - \frac{L_s}{R_v T} \right)\]