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<[email protected]>
User-Agent: Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20120327
Thunderbird/11.0.1
To: "[email protected]"<[email protected]>
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
_______________________________________________
CF-metadata mailing list
[email protected]
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
--
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: [email protected]
--
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
_______________________________________________
CF-metadata mailing list
[email protected]
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
