saturation_mixing_ratio#

metpy.calc.saturation_mixing_ratio(total_press, temperature)[source]#

Calculate the saturation mixing ratio of water vapor.

This calculation is given total atmospheric pressure and air temperature.

Parameters:

total_press (pint.Quantity) – Total atmospheric pressure
temperature (pint.Quantity) – Air temperature

Returns:

pint.Quantity – Saturation mixing ratio, dimensionless

Examples

>>> from metpy.calc import saturation_mixing_ratio
>>> from metpy.units import units
>>> saturation_mixing_ratio(983 * units.hPa, 25 * units.degC).to('g/kg')
<Quantity(20.7079932, 'gram / kilogram')>

Notes

This function is a straightforward implementation of the equation given in many places, such as [Hobbs1977] pg.73:

\[r_s = \epsilon \frac{e_s}{p - e_s}\]

Changed in version 1.0: Renamed tot_press parameter to total_press