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:cameronsmith1 at llnl.gov>
> *To:* Wright, Bruce <mailto:bruce.wright at metoffice.gov.uk> ;
> cf-metadata at cgd.ucar.edu <mailto:cf-metadata at cgd.ucar.edu>
> *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, pjc at llnl.gov, Lawrence Livermore National Lab.
>
> -----------------------------------------------------------------------
>
> *From:*cf-metadata-bounces at cgd.ucar.edu
> [mailto:cf-metadata-bounces at cgd.ucar.edu] *On Behalf Of *Wright, Bruce
> *Sent:* Tuesday, May 15, 2012 7:21 AM
> *To:* cf-metadata at cgd.ucar.edu
> *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:taylor13 at llnl.gov]
> *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
>
> ------------------------------------------------------------------------
>
Received on Wed May 16 2012 - 04:50:59 BST
