relhum

Computes the relative humidity from temperature, specific humidity and logarithm of surface pressure (LNSP) GRIB data. LNSP is only required if the input data is specified on ECMWF model levels.

When the result is a Fieldset the ecCodes paramId in the output is set to 157 (=relative humidity).

The computation is based on the following formula:

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

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())

• q is the specific humidity

• p is the pressure

• t is the temperature

Note

This function performs the same task as the Relative Humidity icon in Metview’s user interface. It accepts its parameters as keyword arguments, described below.

relhum(**kwargs)

Computes the relative humidity from temperature and specific humidity GRIB data.

Parameters

data (Fieldset) – Specifies the temperature and specific humidity input GRIB data required for the application. If the input is defined on ECMWF (hybrid/eta) model levels it must contain a Logarithm of Surface Pressure field as well (it must have the ecCodes paramId of 152).

Return type

Fieldset

Gallery examples using metview.relhum

Cross Section 3D Wind in Height for Model Level Data