relative_humidity_from_mixing_ratio#

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

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

Parameters:

  • pressure (pint.Quantity) – Total atmospheric pressure

  • temperature (pint.Quantity) – Air temperature

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

  • 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 – Relative humidity

Examples

>>> from metpy.calc import relative_humidity_from_mixing_ratio
>>> from metpy.units import units
>>> relative_humidity_from_mixing_ratio(1013.25 * units.hPa,
...                                     30 * units.degC, 18/1000).to('percent')
<Quantity(67.3008484, 'percent')>

See also

mixing_ratio_from_relative_humidity, saturation_mixing_ratio

Notes

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

\[RH = \frac{w}{\epsilon + w} \frac{\epsilon + w_s}{w_s}\]

  • \(w\) 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 (mixing_ratio, temperature, pressure)