metpy.calc.mixing_ratio_from_relative_humidity(pressure, temperature, relative_humidity)[source]#

Calculate the mixing ratio from relative humidity, temperature, and pressure.

  • pressure (pint.Quantity) – Total atmospheric pressure

  • temperature (pint.Quantity) – Air temperature

  • relative_humidity (array-like) – The relative humidity expressed as a unitless ratio in the range [0, 1]. Can also pass a percentage if proper units are attached.


pint.Quantity – Mixing ratio (dimensionless)


>>> from metpy.calc import mixing_ratio_from_relative_humidity
>>> from metpy.units import units
>>> p = 1000. * units.hPa
>>> T = 28.1 * units.degC
>>> rh = .65
>>> mixing_ratio_from_relative_humidity(p, T, rh).to('g/kg')
<Quantity(15.7646969, 'gram / kilogram')>


Employs [WMO8] eq. 4.A.16 as derived from WMO relative humidity definition based on vapor partial pressures (eq. 4.A.15).

\[RH = \frac{w}{\epsilon + w} \frac{\epsilon + w_s}{w_s}\]
\[\therefore w = \frac{\epsilon * w_s * RH}{\epsilon + w_s (1 - RH)}\]
  • \(w\) is mixing ratio

  • \(w_s\) is the saturation mixing ratio

  • \(\epsilon\) is the molecular weight ratio of vapor to dry air

  • \(RH\) is relative humidity as a unitless ratio

Changed in version 1.0: Changed signature from (relative_humidity, temperature, pressure)

Examples using metpy.calc.mixing_ratio_from_relative_humidity#

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