Forwarding to list because I forgot to do 'reply all'.
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email: alison.pamment at stfc.ac.uk
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:
> alison.pamment at stfc.ac.uk
> STFC Rutherford Appleton Laboratory
> R25, 2.22
> Harwell Campus, Didcot, OX11 0QX, U.K.
>
>
>
> > -----Original Message-----
> > From: Dirk Notz [mailto:dirk.notz at mpimet.mpg.de]
> > Sent: 05 August 2016 12:25
> > To: Pamment, Alison (STFC,RAL,RALSP); cf-metadata at cgd.ucar.edu
> > 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
Received on Fri Aug 05 2016 - 07:19:50 BST
