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Anchor saturation_vapour_pressure saturation_vapour_pressure
number saturation_vapour_pressure(t: number)
number saturation_vapour_pressure(t: number, phase)
Computes the saturation vapour pressure for a given temperature and phase, where
t: the temperature (K)phase: is either "water", "ice" or "mixed". When it is not specified the "water" phase is used.
The result is the saturation vapour pressure in Pa units. On error nil is returned. The computations for saturation over "water" and "ice" are based on the Tetens formula:
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e_{sat} = a_{1}\;exp \left(a_{3}\frac{T-273.16}{T-a_{4}}\right) |
where the parameters are set follows
"water":a1=611.21 Pa,a3=17.502 anda4=32.19 K"ice":a1=611.21 Pa,a3=22.587 anda4=-0.7 K
For the "mixed" phase the linear combination of the "water" and "ice" phases are used as described in the IFS documentation (see mixed-phase Tetens formula used by IFS for diagnostic purposes. See here on p116 for details from the latest for model cycle ( CY45R1) at the time of the writing of this documentation.
fieldset seqpott_m(...)
Computes the saturation equivalent potential temperature from fieldsets on (hybrid) model levels. This is a Metview icon function, for detailed documentation please see Potential Temperature.
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