Dear Heiko,
> 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.
I'm afraid that I find this confusing - surely the proposed
high/middle/low_type_cloud_area_fraction are quite clearly *not*
height based, and would only be applicable to the type of model that
Eizi suggests:
> 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.
All the best,
David
---- Original message from Heiko Klein (12PM 16 May 12)
> Date: Wed, 16 May 2012 12:50:59 +0200
> From: Heiko Klein <Heiko.Klein at met.no>
> User-Agent: Mozilla/5.0 (X11; Linux i686; rv:12.0) Gecko/20120428
> Thunderbird/12.0.1
> To: TOYODA Eizi <toyoda at gfd-dennou.org>
> CC: cf-metadata at cgd.ucar.edu, "Cameron-smith, Philip"
> <cameronsmith1 at llnl.gov>
> Subject: Re: [CF-metadata] FW: Standard_name for cloud-cover by phenomenon
>
> 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
> >
> > ------------------------------------------------------------------------
> >
> _______________________________________________
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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
Received on Wed May 16 2012 - 05:40:38 BST
