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Relative Humidity

Performs a variable conversion from specific_humidity (or mixing ratio), temperature, and pressure to relative humidity. The newly calculated variable is included in the same obs space.

Transform: ["RelativeHumidity"]

obs filters:
- filter: Variables Transform
Transform: ["RelativeHumidity"]
Method: UKMO
Formulation: Sonntag

Observation parameters needed (JEDI name)

  • specific_humidity (q)
  • air_temperature (T)
  • air_pressure or surface_pressure (P)
  • humidity_mixing_ratio (w) (needed when using Method: UKMOmixingratio)

Method(s) available

Various methods are available, shared across all center options. (Any setting of METHOD will result in using formulations associated with the method.) Setting METHOD can be omitted.

options:
  • methodDEFAULT
  • methodUKMOmixingratio
  • methodUKMO

The relative humidity (Rh) is retrieved as follow:

Rh = w/w_{sat}

with w_{sat} (saturated water vapor mixing ratio) derived using e_{sat} (saturated vapor pressure):

w_{sat} = \epsilon \times e_{sat}/(P-e_{sat})

and w (water vapor mixing ratio) derived using q (specific humidity):

w = q/(1-q)

\epsilon is ratio of the gas constant for dry air (R_{d}) over the gas constant for water vapor (R_{v}). The value of e_{sat} (saturated vapor pressure) is derived using :ref:`SatVaporPres_fromTemp`.

Formulation(s) available

Various formulations are available to derive :ref:`SatVaporPres_fromTemp`.

Specific Humidity

Performs a variable conversion from relative humidity, temperature, and pressure to specific humidity. The newly calculated variable is included in the same obs space.

Transform: ["SpecificHumidity"]

obs filters:
- filter: Variables Transform
Transform: ["SpecificHumidity"]
Method: UKMO
Formulation: Sonntag

Observation parameters needed (JEDI name)

  • relative_humidity (Rh)
  • air_temperature (T)
  • air_pressure or surface_pressure (P)

Method(s) available

Only one method is avalable, shared accross all center options. (Any setting of METHOD will result in using this unique method.) Setting METHOD can be omitted.

The specific humidity (q) is retrieved as follows:

q = w/(1+w)

where water vapor mixing ratio (w) is derived from relative humidity (Rh)

w = Rh \times w_{sat}

with w_{sat} (saturated water vapor mixing ratio) derived using e_{sat} (saturated vapor pressure):

w_{sat} = \epsilon \times e_{sat}/(P-e_{sat})

With \epsilon is ratio of the gas constant for dry air (R_{d}) over the gas constant for water vapor (R_{v}). The value of e_{sat} (saturated vapor pressure) is derived using :ref:`SatVaporPres_fromTemp`.

Formulation(s) available

Various formulation are available to derive :ref:`SatVaporPres_fromTemp`.