specific_humidity_from_relative_humidity

specific_humidity_from_relative_humidity(t, r[, p])

New in Metview version 5.14.0.

Computes the specific humidity from the given temperature (t), relative_humidity (r) and pressure (p).

Parameters

t (number, ndarray or Fieldset) – temperature (K)
r (number, ndarray or Fieldset) – relative_humidity (%)
p (number, ndarray or Fieldset) – pressure (Pa)

Return type

same type as t or None

The result is the specific humidity in kg/kg units. On error None is returned. The following rules are applied when t and r are Fieldset objects:

if t is a pressure level Fieldset no p is needed
if t is defined on ECMWF model levels (hybrid/eta) p must be either a single LNSP (logarithm of surface pressure, identified by paramId=152) field or a Fieldset defining the pressure on the same levels as t
for other level types p must be a Fieldset defining the pressure on the same levels as t

When the result is a Fieldset the ecCodes paramId in the output is set to 133 (=specific humidity).

The computation is based on the following equation:

\[r = 100 \frac {e(q, p)}{e_{msat}(t)}\]

where:

e is the vapour pressure (see vapour_pressure())
e_msat is the saturation vapour pressure based on the “mixed” phase (see saturation_vapour_pressure())
t is the temperature
r is the relative humidity

Note