Hei David,
I'm not familiar with the ISCCP datasets, but in a fast look on there
web-page, it seems like the have already a translation to the 3 WMO
clouds:
http://isccp.giss.nasa.gov/cloudtypes.html
It is not that we run a 3 layer model. We compare our 20-130 layer
models, and we do it on the basis of the WMO cloud types, so, like
ISCCP, we have routines to reduce our model-levels to WMO cloud types.
It would of course be possible to introduce a new vertical axis of name
'cloud_type' which is a index list of the different clouds. This would
be more difficult for a general reader, in particular parsing the
['low', 'medium', 'high'] axis will be cumbersome and error-prone.
On the other hand, CF usually describes different phenomenons with
different standard_names, e.g. *_longwave_energy <-> *_shortwave_energy,
swell wave <-> wave rather than with additional axes.
Best regards,
Heiko
On 2012-04-25 12:36, David Hassell wrote:
> Hello Heiko,
>
> I don't have a strong opinion, but am just testing the water ...
>
> I wonder how one would define these standard names so that they were
> correct for all uses, for example from a three layer model to the
> ISCCP datasets.
>
> In your example, would a model_level_number coordinate of [1, 2, 3]
> fit your needs, possibly with an auxiliary coordinate of ['low',
> 'medium', 'high']? Would we need a standard name for the auxiliary
> coordinate, or would a long name suffice?
>
> All the best,
>
> David
>
> ---- Original message from Heiko Klein (11AM 25 Apr 12)
>
>> Date: Wed, 25 Apr 2012 11:49:06 +0200
>> From: Heiko Klein<Heiko.Klein at met.no>
>> User-Agent: Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20120327
>> Thunderbird/11.0.1
>> To: "cf-metadata at cgd.ucar.edu"<cf-metadata at cgd.ucar.edu>
>> Subject: [CF-metadata] Standard_name for cloud-cover by phenomenon
>>
>> Hei,
>>
>> in grib, clouds are described as low, medium and high clouds, e.g.
>> 73,74,75. Those are described by phenomenon, e.g.
>>
>> high cloud type: Clouds of genera Cirrus, Cirrocumulus and Cirrostratus.
>>
>> low cloud type: Clouds of genera Stratocumulus, Stratus, Cumulus, etc.
>>
>> medium cloud type: Clouds of the genera Altocumulus, Altostratus, etc.
>>
>> (see
>>
>> In CF, this can currently only be expressed by
>> cloud_area_fraction_in_atmosphere_layer and a not very well defined
>> 'vertical' parameter, e.g. by sigma:
>> http://www.ecmwf.int/products/data/archive/data_faq.html#clouddefinitions
>>
>>
>> When translating from grib to CF, this is not very satisfying:
>> Either I add some dummy sigma-values, which will look like I have a
>> model with just three levels, or I use 3 variables, all with the
>> same 'standard_name="cloud_area_fraction"' which looses some useful
>> information. In both cases, the data-user will need to know
>> something which cannot be expressed by CF.
>>
>>
>> Looking at the page
>> http://cf-pcmdi.llnl.gov/documents/cf-standard-names/ecmwf-grib-mapping
>> there are mentioned 3 'standard_names' which are not in the
>> standard_name-table yet, and I propose to do so:
>>
>> low_cloud_area_fraction
>> medium_cloud_area_fraction
>> high_cloud_area_fraction
>>
>> in additon (though this is not in grib), I would like to add
>> fog_area_fraction (or surface_cloud_area_fraction).
>>
>>
>> Best regards,
>>
>> Heiko
>>
>> _______________________________________________
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>> CF-metadata at cgd.ucar.edu
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>
>
> --
> David Hassell
> National Centre for Atmospheric Science (NCAS)
> Department of Meteorology, University of Reading,
> Earley Gate, PO Box 243,
> Reading RG6 6BB, U.K.
>
> Tel : 0118 3785613
> Fax : 0118 3788316
> E-mail: d.c.hassell at reading.ac.uk
--
Dr. Heiko Klein Tel. + 47 22 96 32 58
Development Section / IT Department Fax. + 47 22 69 63 55
Norwegian Meteorological Institute http://www.met.no
P.O. Box 43 Blindern 0313 Oslo NORWAY
Received on Wed Apr 25 2012 - 05:22:51 BST
