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.kl...@met.no> > User-Agent: Mozilla/5.0 (X11; Linux i686; rv:12.0) Gecko/20120428 > Thunderbird/12.0.1 > To: TOYODA Eizi <toy...@gfd-dennou.org> > CC: cf-metadata@cgd.ucar.edu, "Cameron-smith, Philip" > <cameronsmi...@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:cameronsmi...@llnl.gov> > > *To:* Wright, Bruce <mailto:bruce.wri...@metoffice.gov.uk> ; > > cf-metadata@cgd.ucar.edu <mailto:cf-metadata@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, p...@llnl.gov, Lawrence Livermore National Lab. > > > > ----------------------------------------------------------------------- > > > > *From:*cf-metadata-boun...@cgd.ucar.edu > > [mailto:cf-metadata-boun...@cgd.ucar.edu] *On Behalf Of *Wright, Bruce > > *Sent:* Tuesday, May 15, 2012 7:21 AM > > *To:* cf-metadata@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:taylo...@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 > > > > ------------------------------------------------------------------------ > > > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > 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: d.c.hass...@reading.ac.uk _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
