Forwarding to list because I forgot to do 'reply all'. ------ Alison Pamment Tel: +44 1235 778065 Centre for Environmental Data Analysis Email: [email protected] STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Campus, Didcot, OX11 0QX, U.K.
> -----Original Message----- > From: Pamment, Alison (STFC,RAL,RALSP) > Sent: 05 August 2016 13:51 > To: 'Dirk Notz' > Subject: RE: [CF-metadata] CMIP6 Sea Ice MIP: Integrated quantities > > Dear Dirk, > > Yes, I'm pleased too that we seem to have agreed these terms. The changes > to sea_ice_extent and sea_ice_volume, i.e. the addition of the definitions, > are accepted for publication in the standard name table. These will be > added on September 13th. > > Best wishes, > Alison > > ------ > Alison Pamment Tel: +44 > 1235 778065 > Centre for Environmental Data Analysis Email: > [email protected] > STFC Rutherford Appleton Laboratory > R25, 2.22 > Harwell Campus, Didcot, OX11 0QX, U.K. > > > > > -----Original Message----- > > From: Dirk Notz [mailto:[email protected]] > > Sent: 05 August 2016 12:25 > > To: Pamment, Alison (STFC,RAL,RALSP); [email protected] > > Subject: Re: [CF-metadata] CMIP6 Sea Ice MIP: Integrated quantities > > > > Dear Alison, > > > > thank you very much for your quick reply, I'm very glad that we seem to > > converge to a good solution on how to add the requested sea-ice > > variables to the CF convention. In particular, I certainly appreciate > > that the concept of sea-ice extent is quite confusing, and that a clear > > definition is certainly required. Notwithstanding such definition, we > > discourage the use of sea-ice extent for model evaluation in CMIP6 > > SIMIP, for the reasons outlined here: > > http://www.the-cryosphere.net/8/229/2014/ > > > > In detail: > > > > > > > So we will use the existing name > > > sea_ice_extent (m2). > > > The definition should be amended to make it a requirement to supply > the > > threshold and to say something about the geographical area over which > > extent is calculated: > > > 'The term sea_ice_extent means the total area of all grid cells in which > the > > sea ice area fraction equals or exceeds a threshold, often chosen to be 15 > > per cent. The threshold must be specified by supplying a coordinate > > variable or scalar coordinate variable with the standard name of > > sea_ice_area_fraction. The horizontal domain over which sea ice extent is > > calculated is described by the associated coordinate variables and > > coordinate bounds or by a coordinate variable or scalar coordinate variable > > with the standard name of "region" supplied according to section 6.1.1 of > > the CF conventions.' > > > > > > OK? > > > > This sounds very good to me. > > > > > > > > > > I have checked the CF conventions document again regarding this point. > > Section 6.1.1, "Geographic regions", states: "When data is representative > of > > geographic regions which can be identified by names but which have > > complex boundaries that cannot practically be specified using longitude > and > > latitude boundary coordinates, a labeled axis should be used to identify > the > > regions. We recommend that the names be chosen from the list of > > standardized region names whenever possible. To indicate that the label > > values are standardized the variable that contains the labels must be given > > the standard_name attribute with the value region." In the case of the > > northern and southern hemispheres, the boundaries are not "complex" > and > > can conveniently be described using the usual coordinate variables, so I > > think in fact we should stick to doing that for CMIP6. In the definition of > the > > name I have allowed for the use of a 'region' coordinate or scalar > coordinate > > variable because it is conceivable that someone may at some stage wish to > > calculate sea_ice_extent over an irregularly shaped area. However, I now > > think that we don't need to add northern_hemisphere and > > southern_hemisphere to the standardized region list. OK? > > > > > > > I fully agree, thanks for looking this up! > > > > Sea-ice area: > > > > > > We should stick with using sea_ice_area, as currently defined, for this > > quantity. > > > > > > > Great, thanks! > > > > Sea-ice volume: > > > Agreed. So we will use the existing name > > > sea_ice_volume (m3) > > > and add the definition: > > > ' "X_volume" means the volume occupied by X within the grid cell.' > > > OK? > > > > Yes, this is good, thanks! > > > > > I appreciate that we may not be able to finalise all the sea ice names > > during August when many people are on leave. The next update of the > > standard name table won't take place until September 13th (again due to > > the holiday season) so we might be able to agree some, if not all, the > names > > by then. We need to expand on the definition text for all the proposed > > names to bring them into line with existing names so I will prepare a list > > summarizing the current state of play, with full definitions, ready for you > to > > review once you are back in the office. > > > > Great, we'd be very happy to have further comments and/or suggestions > > regarding our proposed variables. I find the exchange on this email list > > to be truly helpful and extremely constructive. Thanks to everyone! > > > > All the best for now, > > > > Dirk _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
