Dear Jakob,
To try to answer your specific query first: the correct spelling of the standard name is lwe_thickness_of_atmosphere_water_vapor_content. You are correct that standard names should always use the American spelling. The units associated with this standard name are m and the explanation is as follows: " "lwe" means liquid water equivalent. The construction lwe_thickness_of_X_amount or _content means the vertical extent of a layer of liquid water having the same mass per unit area. "Content" indicates a quantity per unit area. The "atmosphere content" of a quantity refers to the vertical integral from the surface to the top of the atmosphere. For the content between specified levels in the atmosphere, standard names including content_of_atmosphere_layer are used. Atmosphere water vapor content is sometimes referred to as "precipitable water", although this term does not imply the water could all be precipitated."
If you are looking for a quantity with units of kg m-2 then the standard name to use is "atmosphere_water_vapor_content" which has the following explanation: " "Content" indicates a quantity per unit area. The "atmosphere content" of a quantity refers to the vertical integral from the surface to the top of the atmosphere. For the content between specified levels in the atmosphere, standard names including content_of_atmosphere_layer are used. Atmosphere water vapor content is sometimes referred to as "precipitable water", although this term does not imply the water could all be precipitated."
Hence, the correct standard name equivalent to GRIB code 137 depends on the units that are normally associated with that parameter, which is something I need to check.
Regarding your broader point, you are correct that there are differences between the two documents - the one on the CF website was originally created by Jonathan Gregory to demonstrate that equivalences can be made between CF standard names and other ways of identifying parameters. I don't think it was ever really intended as a reference document and in fact some of the mappings are incorrect. Also, it pre-dates the use of GRIB2 as a data format. We should probably remove it from the CF website and instead include a link to the ECMWF table which is more up to date and which, I believe, is being actively maintained. However, I think that some of the equivalences shown in the ECMWF table are also not entirely correct, as demonstrated by your query. I will pass this on to ECMWF and try to get a definitive answer to your question. If you notice anything else in the ECMWF table that looks strange, please let me know and I'll feed it back to them.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
STFC Rutherford Appleton Laboratory Email: alison.pamment at stfc.ac.uk
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
> -----Original Message-----
> From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-
> bounces at cgd.ucar.edu] On Behalf Of Malm Jakob
> Sent: 02 February 2011 08:30
> To: cf-metadata at cgd.ucar.edu
> Subject: [CF-metadata] ECMWF GRIB code - CF Standard Name Mapping
> incorrect?
>
> There are differences between the CF standard names on
>
> http://cf-pcmdi.llnl.gov/documents/cf-standard-names/ecmwf-grib-mapping
> [CF document]
>
> and
>
> http://www.ecmwf.int/publications/manuals/d/gribapi/param/ [ECMWF
> site] (click on the netcdf link for any particular parameter)
>
> E.g. tcwv:
>
> [CF document]:
> GRIB code Units ECMWF CF ECMWF description CF
> Standard Name
> 137 m (of water) m Precipitable Water Content
> lwe_thickness_of_atmosphere_water_vapour_content
>
> [ECMWF site]
> (http://www.ecmwf.int/publications/manuals/d/gribapi/param/detail/forma
> t=netcdf/pid=137/):
> paramId 137
> shortName tcwv
> name Total column water vapour
> unit kg m**-2
> description Vertically integrated water vapour
> cfname lwe_thickness_of_atmosphere_water_vapor_content
>
> The most important difference is the units, where the CF document says
> 'm', and ECMWF says 'kg m**-2' (which is the correct unit for the tcwv
> parameter). Does the ECMWF parameter have an incorrect CF name or are
> the units in the CF document wrong?
>
> I am also puzzled to see the spelling 'vapour', because I thought that
> the American spellings (vapor, color...) were the CF standard.
>
>
> Jakob Malm
> SMHI
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
--
Scanned by iCritical.
Received on Wed Feb 02 2011 - 04:33:52 GMT
