earthkit.meteo.thermo.fieldlist.mixing_ratio_from_dewpoint

earthkit.meteo.thermo.fieldlist.mixing_ratio_from_dewpoint(td, p=None)

Compute the mixing ratio from dewpoint.

Parameters:

• td (FieldList|Field) – Dewpoint (K).

• p (FieldList|Field|Iterable[float]|float|None) – Pressure (Pa). If None, inferred from the field metadata of td. Otherwise, if td is a FieldList p must be a FieldList or an array-like of the same length as td. If td is a Field, p must be a single Field or a float.

Returns:

Mixing ratio (kg/kg). The result has the same type as the input td (FieldList or Field).

Return type:

FieldList|Field

The computation starts with determining the vapour pressure:

\[e(w, p) = e_{wsat}(td)\]

where:

• \(e\) is the vapour pressure (see vapour_pressure_from_mixing_ratio())

• \(e_{wsat}\) is the saturation_vapour_pressure() over water

• \(w\) is the mixing ratio

Then w is computed from \(e\) using mixing_ratio_from_vapour_pressure().