earthkit.meteo.thermo.fieldlist.dewpoint_from_specific_humidity

earthkit.meteo.thermo.fieldlist.dewpoint_from_specific_humidity(q, p=None)

Compute the dewpoint temperature from specific humidity.

Parameters:

• q (FieldList|Field) – Specific humidity (kg/kg).

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

Returns:

Dewpoint temperature (K). For zero q values returns nan. The result has the same type as the input q (FieldList or Field).

Return type:

FieldList|Field

The computation starts with determining the saturation vapour pressure over water at the dewpoint temperature:

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

where:

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

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

• \(td\) is the dewpoint

Then \(td\) is computed from \(e_{wsat}(td)\) by inverting the equations used in saturation_vapour_pressure().