vapour_pressure
- vapour_pressure(q[, p])
Computes the vapour pressure for a given specific humidity (
q
) and pressure (p
).- Parameters
- Return type
same type as
q
or None
The result is the vapour pressure in Pa units. On error None is returned. The following rules are applied when
q
is aFieldset
:if
q
is a pressure levelFieldset
nop
is neededif
q
is defined on ECMWF model levels (hybrid/eta)p
must be either a single LNSP (logarithm of surface pressure, identified by paramId=152) field or aFieldset
defining the pressure on the same levels asq
for other level types
p
must be aFieldset
defining the pressure on the same levels asq
.
The computation is based on the following formula:
\[\frac{p\;q}{\epsilon\; (1 + q(\frac{1}{\epsilon} -1 ))}\]with
\[\epsilon = \frac{R_{dry}}{R_{vapour}} = 0.621981\]