"Surface air specific humidity" could look like belowGRIB-API definition
| name | 2 metre relative humidity | Abbreviation |
rh
UERRA details
| Definition | The ratio of the partial pressure of water |
vapor | vapour to the equilibrium |
vapor | vapour pressure of water at the same temperature near the surface. |
| Validity | instantaneous |
| Comment | Please note that the specific height level above ground might vary from one Centre to another. |
The scaled value of first fixed surface given below is the one in usage at ECMWF.
WMO GRIB2 definition
| Parameter |
|---|
| Discipline | 0 | meteorological products |
| Parameter Category | 1 | moisture |
| Parameter Number | 1
| relative humidity
|
| Level |
|---|
| Type of first fixed surface | 103 |
| specified height level above ground (m) |
| Scale factor of first fixed surface | 0 |
|
| Scaled value of first fixed surface | 2 |
2m (might vary from one centre to another)| or 15*** | 2 / 1.5 m |
| Type of second fixed surface | all bits to 1 | missing
|
| Scale factor of second fixed surface | all bits to 1 | missing |
| Scaled value of second fixed surface | all bits to 1 | missing |
*** option valid for MetOffice