GRIB-API definition

name2 metre relative humidityAbbreviation2rUnit%paramId:260242

 

UERRA details

DefinitionThe ratio of the partial pressure of water vapour to the equilibrium vapour pressure of water at the same temperature near the surface.
Validity

instantaneous

CommentPlease note that the specific height level above ground might vary from one Centre to another.

 

WMO GRIB2 definition

Parameter
Discipline0meteorological products
Parameter Category1moisture
Parameter Number1
relative humidity
Level
Type of first fixed surface103specified height level above ground (m)
Scale factor of first fixed surface0 or 1***(m) or (dm***)
Scaled value of first fixed surface2 or 15***2 / 1.5 m
Type of second fixed surfaceall bits to 1missing
Scale factor of second fixed surfaceall bits to 1missing
Scaled value of second fixed surfaceall bits to 1missing

*** option valid for MetOffice

 

6 Comments

  1. Richard Mladek

    It would be consistent with up-to-now approach to call this parameter "2 metre relative humidity" (with abbreviation 2r) in GRIB-API. The more general name "Surface air relative humidity" would be beneficial sometimes as some centres measure at 1.5m height.

  2. Sebastien Villaume

    I don' t see how you could resolve having one paramId but 2 definitions, one for 2m and one for 1.5m ....it would work for getting a paramid out of the message but which one should be picked when you set the paramId?

    The only solution I could think of is to add centre=74 explicitly in the concept and have this one appearing before the default one in paramId.def.

    what do you think Shahram Najm?

  3. Shahram Najm

    We can adopt the same approach as we did for params 121,167,168 and the override for the UKMO (their TWO metre XX is actually 1.5 metres!)

  4. Sebastien Villaume

    lets do it then

  5. Sebastien Villaume

    Shahram Najm: should I create a specific issue for this? (since you create a specific one for cloud cover in %)

  6. Shahram Najm

    Yes please. Raise a JIRA issue