metpy.calc.density(pressure, temperature, mixing_ratio, molecular_weight_ratio=<Quantity(0.62195691, 'dimensionless')>)[source]#

Calculate density.

This calculation must be given an air parcel’s pressure, temperature, and mixing ratio. The implementation uses the formula outlined in [Hobbs2006] pg.67.

  • pressure (pint.Quantity) – Total atmospheric pressure

  • temperature (pint.Quantity) – Air temperature (or the virtual temperature if the mixing ratio is set to 0)

  • mixing_ratio (pint.Quantity) – Mass mixing ratio (dimensionless)

  • molecular_weight_ratio (pint.Quantity or float, optional) – The ratio of the molecular weight of the constituent gas to that assumed for air. Defaults to the ratio for water vapor to dry air. (\(\epsilon\approx0.622\))


pint.Quantity – Corresponding density of the parcel


>>> from metpy.calc import density
>>> from metpy.units import units
>>> density(1000 * units.hPa, 10 * units.degC, 24 * units('g/kg'))
<Quantity(1.21307146, 'kilogram / meter ** 3')>


\[\rho = \frac{\epsilon p\,(1+w)}{R_dT\,(w+\epsilon)}\]

Changed in version 1.0: Renamed mixing parameter to mixing_ratio