earthkit.meteo.thermo.saturation_ept

earthkit.meteo.thermo.saturation_ept(t: ArrayLike, p: ArrayLike, method: str = 'ifs') → ArrayLike

earthkit.meteo.thermo.saturation_ept(t: xarray.DataArray, p: xarray.DataArray, method: str = 'ifs') → xarray.DataArray

earthkit.meteo.thermo.saturation_ept(t: earthkit.data.FieldList, p: earthkit.data.FieldList, method: str = 'ifs') → earthkit.data.FieldList

Compute the saturation equivalent potential temperature.

Parameters:

• t (number or array-like) – Temperature (K)

• p (number or array-like) – Pressure (Pa)

• method (str, optional) – Specifies the computation method. The possible values are: “ifs”, “bolton35”, “bolton39”.

Returns:

Saturation equivalent potential temperature (K)

Return type:

number or array-like

The actual computation is based on the method:

• “ifs”: The formula is based on the equivalent potential temperature definition used

  in the IFS model [IFS-CY47R3-PhysicalProcesses] (see Chapter 6.11) :

  \[\Theta_{esat} = \Theta \operatorname{exp}(\frac{L_{v} q_{sat}}{c_{pd} t})\]

• “bolton35”: Eq (35) from [Bolton1980] is used:

  \[\Theta_{e} = \Theta (\frac{10^{5}}{p})^{\kappa 0.28 w_{sat}} \operatorname{exp}(\frac{2675 w_{sat}}{t})\]

• “bolton39”: Eq (39) from [Bolton1980] is used:

  \[\Theta_{e} = t (\frac{10^{5}}{p-e_{sat}})^{\kappa} \operatorname{exp}[(\frac{3036}{t} - 1.78)w_{sat}(1+0.448 w_{sat})]\]

where:

• \(\Theta\) is the potential_temperature()

• \(e_{sat}\) is the saturation_vapor_pressure()

• \(q_{sat}\) is the saturation_specific_humidity()

• \(w_{sat}\) is the saturation_mixing_ratio()

• \(L_{v}\) is the specific latent heat of vaporization (see earthkit.meteo.constants.Lv)

• \(c_{pd}\) is the specific heat of dry air on constant pressure (see earthkit.meteo.constants.c_pd)

Implementations

saturation_ept() calls one of the following implementations depending on the type of the input arguments:

• earthkit.meteo.thermo.array.saturation_ept() for array-like

• earthkit.meteo.thermo.xarray.saturation_ept() for xarray.DataArray

• earthkit.meteo.thermo.fieldlist.saturation_ept() for FieldList

The function returns an object of the same type as the input arguments.