vapor_pressure

metpy.calc.vapor_pressure(pressure, mixing_ratio)

Calculate water vapor (partial) pressure.

Given total pressure and water vapor mixing_ratio, calculates the partial pressure of water vapor.

Parameters:

• pressure (pint.Quantity) – Total atmospheric pressure

• mixing_ratio (pint.Quantity) – Dimensionless mass mixing ratio

Returns:

pint.Quantity – Ambient water vapor (partial) pressure in the same units as pressure

Examples

>>> from metpy.calc import vapor_pressure
>>> from metpy.units import units
>>> vapor_pressure(988 * units.hPa, 18 * units('g/kg')).to('hPa')
<Quantity(27.789371, 'hectopascal')>

See also

saturation_vapor_pressure, dewpoint

Notes

This function is a straightforward implementation of the equation given in many places, such as [Hobbs1977] pg.71:

\[e = p \frac{r}{r + \epsilon}\]

Changed in version 1.0: Renamed mixing parameter to mixing_ratio

Examples using metpy.calc.vapor_pressure

Dewpoint and Mixing Ratio

Dewpoint and Mixing Ratio