This icon computes the relative humidity from temperature, specific humidity and logarithm of surface pressure (lnsp) GRIB data. Lnsp is only required if the input data is specified on (hybrid) model levels. The computations are based on the same diagnostic formula as in IFS: the vapour pressure is derived with respect to water above 273.16 K, to ice below 250.16 K, and to a mixed phase in between. See the IFS documentation at http://www.ecmwf.int/research/ifsdocs/ for details.
From script (Macro/Python) the icon can be called as relhum().
The Relative Humidity Editor
Data
Specifies the temperature and specific humidity GRIB data required for the application. If the input is on (hybrid) model levels it must contain the lnsp field as well.