please may I obtain confirmation that this change is now amenable and will be included in the next release of the standard names vocabulary?
Explicitly: I would like to formally propose that the description text for standard names: low_type_cloud_area_fraction medium_type_cloud_area_fraction high_type_cloud_area_fraction be altered such that 'X_type_cloud_area_fraction is determined on the basis of cloud type and not on the vertical location of the cloud.' instead reads 'X_type_cloud_area_fraction is generally determined on the basis of cloud type, though numerical weather prediction models often calculate them based on the vertical location of the cloud.' thank you mark ________________________________________ From: Heiko Klein [[email protected]] Sent: 27 June 2014 09:30 To: John Graybeal; Hedley, Mark Cc: CF Metadata List; Alison Pamment Subject: Re: [CF-metadata] cloud amounts NWP = numerical weather prediction Heiko On 2014-06-19 17:50, John Graybeal wrote: > I like the change, but please spell out NWP (and if a proper noun, make sure > it is an unambiguous reference for anyone in the world). > > john > > On Jun 19, 2014, at 03:55, Hedley, Mark <[email protected]> wrote: > >> Hi Heiko, Alison, CF >> >> that all sounds good to me, many thanks for your input and advice Heiko >> >> I would like to formally propose that the description text for standard >> names: >> low_type_cloud_area_fraction >> medium_type_cloud_area_fraction >> high_type_cloud_area_fraction >> >> be altered such that >> >> 'X_type_cloud_area_fraction is determined on the basis of cloud type and >> not on the vertical location of the cloud.' >> >> instead reads >> >> 'X_type_cloud_area_fraction is generally determined on the basis of cloud >> type, though NWP models often calculate them based on the vertical location >> of the cloud.' >> >> thank you >> mark >> ________________________________________ >> From: Heiko Klein [[email protected]] >> Sent: 18 June 2014 08:20 >> To: Hedley, Mark; [email protected] >> Subject: Re: [CF-metadata] cloud amounts >> >> Hi Mark, >> >> the first proposal for the *_cloud_area_fraction was in fact >> high/medium/low, and not high_type etc. But then, we found out that we >> do not manage to give a concise description where a 'high' cloud starts >> and where it ends. The altitude of the clouds changes by latitude and >> other factors. >> >> The 'high/medium/low_type' words are rather concepts than precise model >> descriptions, and when doing inter-comparison from model to model or >> from model to observations it will be possible to do so on that basis. >> >> >> I just reread the description in the standard_name list, and I see that >> only half of the proposal made it the the final list. The sentence: >> >> 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. >> >> didn't make it. >> >> >> >> So, I agree, that the current description needs a slight modification >> because it currently rules out a common usage. I suggest to change from >> >> X_type_cloud_area_fraction is determined on the basis of cloud type and >> not on the vertical location of the cloud. >> >> to >> >> X_type_cloud_area_fraction is generally determined on the basis of cloud >> type, though NWP models often calculate them based on the vertical >> location of the cloud. >> >> >> Otherwise, we might end up with two standard-names describing the same >> concept, just because the description sounds to strict. >> >> >> Best regards, >> >> Heiko >> >> On 2014-06-17 14:57, Hedley, Mark wrote: >>> Hello Heiko, CF >>> >>> Many thanks for your feedback, that is really useful. I think I appreciate >>> the utility of these standard names, the feedback I have had is that >>> diagnostics like this are widely used by forecasters and model analysts. >>> >>> The concerns raised with me relate to the descriptions of these >>> diagnostics, and the focus on 'cloud type identification' for >>> classification. >>> >>> There are similarly named diagnostics in our models, which explicitly do >>> not categorise clouds; they take defined vertical ranges and return data >>> based on the amount of any cloud in a grid box for that range of model >>> levels. >>> >>> The concern is that whilst the standard name is likely to be recognised by >>> model developers and forecasters alike, the description which is bound to >>> this standard name does not describe how these diagnostics are calculated >>> within our model. >>> >>> This has lead to the concern that whilst these seem very useful standard >>> names, they should not be used for our models, as the textual description >>> of the standard names do not reflect the modelled quantity in our case. >>> The |low/medium/high| cloud amount is always determined on the basis of the >>> vertical location of the cloud, not on the cloud type, which is not >>> modelled. >>> >>> Do you think that the description text statement: >>> ''X_type_cloud_area_fraction is determined on the basis of cloud type >>> and not on the vertical location of the cloud.'' >>> properly represents the standard name and its usage across the community? >>> >>> Might we be better served by using a different name for these model >>> outputs, even if this hides the generally accepted interpretation of >>> high/medium/low cloud? (if so, what?) >>> >>> many thanks >>> mark >>> >>> ________________________________________ >>> From: Heiko Klein [[email protected]] >>> Sent: 11 June 2014 18:53 >>> To: Hedley, Mark; [email protected] >>> Subject: Re: [CF-metadata] cloud amounts >>> >>> Hi Mark, >>> >>> I've been the original requestor for the >>> low/middle/high_type_cloud_area_fraction. >>> >>> WMO has introduced the low/middle/high clouds already before models >>> became as famous as they are today, and they still seem to be a >>> excellent simplification and forecasters still use these 3 types (+fog). >>> >>> Model output can come in many levels, currently in Europe between 60 and >>> 200. This is definitely too much to transfer and to handle for a >>> forecaster and a reduction to 3 (4) cloud-types is done at all known >>> centres (Norway/ECMWF/SMHI). You are right that this reduction is often >>> just a summation of certain levels, but it doesn't need to - I've seen >>> at least one model which calculates fog different than just taking >>> clouds in ground-level. >>> >>> Examples: >>> >>> >>> # using correct standard_name >>> http://thredds.met.no/thredds/dodsC/arome25/arome_norway_default2_5km_latest.nc.html >>> >>> >>> # layer named e.g. High cloud cover >>> http://wrep.ecmwf.int/wms/?token=MetOceanIE&request=GetCapabilities&version=1.1.1&service=WMS >>> >>> >>> Concerning your questions: >>> >>> 1. Forecasts are never accurate, but the definitions are at least well >>> established by WMO, and it is the models task to translate them as best >>> as possible >>> >>> 2. No, the cloud types predate models and model levels and eventually >>> accurate height measurements. If a model-level - cloud type assumption >>> is used, this is just a guess. >>> >>> 3. Really good question, I'll ask our modellers how they calculate the >>> different types. >>> >>> Heiko >>> >>> On 2014-06-11 15:41, Hedley, Mark wrote: >>>> Hello CF >>>> >>>> I have been having an interesting conversation with some modelling >>>> colleagues regarding the standard names and descriptions for cloud amount: >>>> >>>> cloud_area_fraction: >>>> 'X_area_fraction' means the fraction of horizontal area occupied by X. >>>> 'X_area' means the horizontal area occupied by X within the grid cell. >>>> Cloud area fraction is also called 'cloud amount' and 'cloud cover'. The >>>> cloud area fraction is for the whole atmosphere column, as seen from the >>>> surface or the top of the atmosphere. The cloud area fraction in a layer >>>> of the atmosphere has the standard name >>>> cloud_area_fraction_in_atmosphere_layer. >>>> >>>> low_type_cloud_area_fraction: >>>> Low type clouds are: Stratus, Stratocumulus, Cumulus, Cumulonimbus. >>>> "X_area_fraction" means the fraction of horizontal area occupied by X. >>>> Cloud area fraction is also called "cloud amount" and "cloud cover". >>>> X_type_cloud_area_fraction is determined on the basis of cloud type and >>>> not on the vertical location of the cloud. >>>> >>>> middle_type_cloud_area_fraction: >>>> Middle type clouds are: Altostratus, Altocumulus, Nimbostratus. >>>> "X_area_fraction" means the fraction of horizontal area occupied by X. >>>> Cloud area fraction is also called "cloud amount" and "cloud cover". >>>> X_type_cloud_area_fraction is determined on the basis of cloud type and >>>> not on the vertical location of the cloud. >>>> >>>> high_type_cloud_area_fraction: >>>> High type clouds are: Cirrus, Cirrostratus, Cirrocumulus. >>>> "X_area_fraction" means the fraction of horizontal area occupied by X. >>>> Cloud area fraction is also called "cloud amount" and "cloud cover". >>>> X_type_cloud_area_fraction is determined on the basis of cloud type and >>>> not on the vertical location of the cloud. >>>> >>>> In our local models, we have diagnostics labelled: >>>> TOTAL CLOUD AMOUNT - RANDOM OVERLAP >>>> LOW CLOUD AMOUNT >>>> MEDIUM CLOUD AMOUNT >>>> HIGH CLOUD AMOUNT >>>> >>>> The model calculates LOW CLOUD AMOUNT by finding the maximum amount of >>>> cloud cover in a model level which exists within a range defined as >>>> low. The model has no inclination about cloud types and makes no >>>> evaluation of overlap for these diagnostics. >>>> >>>> The model calculates TOTAL CLOUD AMOUNT - RANDOM OVERLAP by evaluating >>>> the cloud over all vertical levels and its spatial displacement. >>>> >>>> Base on this, it seems reasonable to use the CF standard name >>>> cloud_area_fraction >>>> for output fields but based on the descriptive text then I do not see >>>> how we could ever be able to use >>>> low_type_cloud_area_fraction >>>> for data output from our model. >>>> >>>> I would be really interested to hear from people who use these standard >>>> names regularly on the applicability to our case; specifically: >>>> >>>> 1. Are these definitions explicit, complete and accurate? >>>> >>>> 2. Should all uses of these standard names be sure that they are based >>>> on typing the cloud correctly, not on the level of the cloud within the >>>> model? >>>> >>>> 3. Do these high/medium/low cloud type standard names also assume that >>>> spatially displaced levels are summed, or are they aiming to report the >>>> maximum in any one level within the range? >>>> >>>> many thanks >>>> mark >>>> >>>> >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> [email protected] >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>>> >>> >>> -- >>> 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 >>> >> >> -- >> 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 > -- 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
