saturation_vapour_pressure

saturation_vapour_pressure(t[, phase])

Computes the saturation vapour pressure for a given temperature (t) and phase.

Parameters

  • t (number, ndarray or Fieldset) – temperature (K)

  • phase (str) – is either “water”, “ice” or “mixed”. When it is not specified the “water” phase is used.

Return type

same type as t or None

The result is the saturation vapour pressure in Pa units. On error None is returned. The computations for saturation over “water” and “ice” are based on the Tetens formula:

\[e_{sat} = a_{1}\;exp \left(a_{3}\frac{T-273.16}{T-a_{4}}\right)\]

where the parameters are set as follows:

  • “water”: a1 =611.21 Pa, a3 =17.502 and a4 =32.19 K

  • “ice”: a1 =611.21 Pa, a3 =22.587 and a4 =-0.7 K

For the “mixed” phase the linear combination of the “water” and “ice” phases is used as described in the IFS documentation (see here on p116 for details for model cycle CY45R1).