Hi,
I agree with Eizi that I would like a std_name which should be used for
comparison between models and measurements. It should follow the synop
description, though it should not be required for models to detect the
cloud-types exactly.
The exact cloud_area_fraction of a model can be described by
'cloud_area_fraction_in_atmosphere_layer' with a corresponding
vertical-layer, but it is difficult to compare it with other models. And
that is what the proposed std_name should be good for.
I would still like to go for the definition of
high/middle/low_type_cloud_area_fraction. Maybe we should add a sentence
to the description like:
The cloud types can be used for models, too, e.g. by the definitions
like (taken from ECMWF):
Let sigma = pressure / surface pressure.
Low type cloud is for 1.0 > sigma > 0.8
Medium cloud is for 0.8 >= sigma > 0.45
High cloud is for 0.45 >= sigma
The definition depends usually on model and/or latitude.
Best regards,
Heiko
On 2012-05-16 07:42, TOYODA Eizi wrote:
Hi Philip,
Very precicely speaking, what we propose is simulation of
high/medium/low cloud area fractions following SYNOP rules. Some
operational NWP models do a kind of simulation of cloud that would be
observed by humans at surface. This is a kind of substitute of manned
surface observation, so I believe it will be useful more and more.
Regarding generality. Some people may consider it roughly compatible
with height-based definitions like ISCCP. It's up to users. But we have
to make definition clear, mainly to avoid comments requesting use of
vertical coordinate variable. Cloud type-based classifications doesn't
have natural vertical coordinate, and new names are only necessary for
such parameters. Height-based classifications can be described with
existing standard name "cloud_area_fraction
<http://cf-pcmdi.llnl.gov/documents/cf-standard-names/standard-name-table/19/cf-standard-name-table.html>"
with vertical coordinate variable.
Synoptic observation (coordinated by WMO) is probably only well-known
type-based classification. And it has been unchanged at least since
1975, and I personally think it isn't likely to change for many years.
Above is my understanding but I believe and hope original proposal from
Heiko is not too far from that.
So now I see no problem to register
high/middle/low_type_cloud_area_fraction .
Best Regards,
Eizi
----- Original Message -----
*From:* Cameron-smith, Philip <mailto:[email protected]>
*To:* Wright, Bruce <mailto:[email protected]> ;
[email protected] <mailto:[email protected]>
*Sent:* Wednesday, May 16, 2012 3:55 AM
*Subject:* Re: [CF-metadata] FW: Standard_name for cloud-cover by
phenomenon
Thanks, Bruce. Those emails helped crystalize it for me.
Heiko, Eizi, are you proposing that the definition of
high/medium/low_type_cloud_area_fraction follow the SYNOP rules precisely?
Or will it be general enough to allow similar protocols, eg from ISCCP?
If it is highly specific then I still feel it would be better to include
the provenance (eg, WMOSYNOP).
If the definition will be somewhat general then I will drop my
objection. I am still not enthusiastic about using the work 'type'
in this way, but I confess that I cannot think of a better alternative.
Best wishes,
Philip
-----------------------------------------------------------------------
Dr Philip Cameron-Smith, [email protected], Lawrence Livermore National Lab.
-----------------------------------------------------------------------
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Wright, Bruce
*Sent:* Tuesday, May 15, 2012 7:21 AM
*To:* [email protected]
*Subject:* [CF-metadata] FW: Standard_name for cloud-cover by phenomenon
Not sure if this was reply from Karl, went to the whole list or just
to me.
Regards,
Bruce
------------------------------------------------------------------------
*From:*Karl Taylor [mailto:[email protected]]
*Sent:* 15 May 2012 15:09
*To:* Wright, Bruce
*Subject:* Re: [CF-metadata] Standard_name for cloud-cover by phenomenon
All,
Also, sorry to step in late and not having read all the
communications on this ... but for your consideration:
In Bruce's second case, wouldn't it be better to use a vertical
coordinate (specifically the bounds on it) to indicate the cloud
layer being considered? The standard name "cloud_area_fraction"
could then be used, and the coordinate would tell whether it was
low, middle, or high (and would also quantitatively specify what is
meant by those qualitative terms).
Best regards,
Karl
On 5/15/12 2:07 AM, Wright, Bruce wrote:
All,
Sorry to wade into this discussion late, but I believe part of the
difficulty experienced in the discussions here are a consequence of
mixing two distinct 'concepts':
1. Cloud Height Classification Based on Cloud Types
There is a well-recognised allocations of cloud types to height-bands.
These types and bands are nicely illustrated both in tabular form and
visually on the Cloud Appreciation Society website at:
http://cloudappreciationsociety.org/collecting/about-cloud-classificatio
ns/
http://cloudappreciationsociety.org/collecting/
I believe that this allocation to height bands is sufficiently
well-known to be characterized without attributing an owner (e.g. WMO)
or an observation process (e.g. SYNOP), as Heiko argued. Thus, (if
required) these should probably be given the standard names:
low_type_cloud_area_fraction
medium_type_cloud_area_fraction
high_type_cloud_area_fraction
*However*, at present I would argue that these can only be accurately
determined by a human inspection of the sky, which leads us to the
second concept...
2. Cloud Height Classification Based on Height Ranges
Most automated systems, be they cloud base recorders, numerical models
or other forecasting processes, will assign a cloud height class based
on a height range. In this case, I would argue that the following set of
standard names are more appropriate:
low_cloud_area_fraction
medium_cloud_area_fraction
high_cloud_area_fraction
I acknowledge that different height ranges will be adopted by different
users, but, as Heiko states, this approach will at least allow
Intercomparison, and the exact details of the height ranges used could
be included as additional (non-CF Standard) metadata.
Having presented these two 'concepts', I would suggest that the second
is likely to be the most useful, in an age where the human observers are
significantly outnumbered by automated observing and forecasting
systems. However, there is no reason why both sets of standard names
could not to adopted.
My contribution to the debate - I hope it's helpful.
Regards,
Bruce
------------------------------------------------------------------------
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