[CF-metadata] CMIP6 Sea Ice MIP: Ice thickness
- Contemporary messages sorted: [ by date ] [ by thread ] [ by subject ] [ by author ] [ by messages with attachments ]
---- Dr. Dirk Notz http://www.mpimet.mpg.de/~notz.dirk Am 21.07.2016 um 15:05 schrieb Jonathan Gregory: > Dear Dirk > > I think I get your point, but nonetheless I would say that the "equivalent > sea ice thickness" can be correctly described by existing conventions. If the > standard_name is sea_ice_thickness and the cell_methods says "area: mean", > the interpretation is that the sea_ice_thickness is integrated over the area > of the grid box and then divided by the grid box area. That is what you want, > isn't it? By contrast the local thickness of sea-ice, at a point, would have > cell_methods with "area: point", and the thickness averaged over the sea-ice > area is "area: mean where sea_ice". Thus the cases are distinguished by the > cell_methods. In the CF convention, the standard_name is only part of the > description of the data variable. > > Best wishes > > Jonathan > > ----- Forwarded message from Dirk Notz <dirk.notz at mpimet.mpg.de> ----- > >> Date: Thu, 21 Jul 2016 13:33:55 +0200 >> From: Dirk Notz <dirk.notz at mpimet.mpg.de> >> To: Jonathan Gregory <j.m.gregory at reading.ac.uk> >> Subject: Re: [CF-metadata] CMIP6 Sea Ice MIP: Ice thickness >> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 >> Thunderbird/45.2.0 >> >> Dear Jonathan, >> >> thanks a lot for your guidance. I understand that >> equivalent_sea_ice_thickness can be constructed from existing mechanisms. >> >> However, the definition of equivalent_sea_ice_thickness is not related >> to actual sea-ice thickness, but simply defined as sea-ice volume per >> grid area. This then only happens to have the same units as >> sea_ice_thickness. We hence initially proposed to have >> equivalent_sea_ice_thickness recorded as sea_ice_volume, but Alison >> pointed out that units of "m" are not possible for any variable that is >> called "volume". >> >> However, given the substantial confusion that arose in some papers >> published with CMIP5 data, where people assumed that "sea_ice_thickness" >> is actual thickness, we believe that it would be worthwhile to add a >> variable with a distinct name to avoid such confusion in the future. >> >> Best, >> >> Dirk >> >> >> >> ---- >> Dr. Dirk Notz >> http://www.mpimet.mpg.de/~notz.dirk >> >> Am 20.07.2016 um 15:21 schrieb Jonathan Gregory: >>> Dear Dirk >>> >>> I believe that this distinction can be recorded by the existing mechanisms >>> of "where" and "over" in cell_methods, using the existing standard_name of >>> sea_ice_thickness. Please see Section 7.3.3 of the CF standard. The grid-box- >>> mean sea-ice thickness is "area: mean where all_area_types" and the thickness >>> meaned over sea-ice only is "area: mean where sea_ice", I think. >>> >>> Best wishes >>> >>> Jonathan >>> >>> ----- Forwarded message from Dirk Notz <dirk.notz at mpimet.mpg.de> ----- >>> >>>> Date: Tue, 19 Jul 2016 09:53:02 +0200 >>>> From: Dirk Notz <dirk.notz at mpimet.mpg.de> >>>> To: cf-metadata at cgd.ucar.edu >>>> Subject: [CF-metadata] CMIP6 Sea Ice MIP: Ice thickness >>>> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 >>>> Thunderbird/38.8.0 >>>> >>>> Dear CF community, >>>> >>>> traditionally, the variable sea_ice_thickness from CMIP-type model >>>> output was calculated by dividing the entire volume of sea ice in a grid >>>> cell by the entire area of the grid cell, independent of the area >>>> fraction of the grid cell that was actually covered by sea ice. >>>> >>>> This gave rise to substantial confusion for users who expected that >>>> sea_ice_thickness as stored within CMIP simulations refers to the actual >>>> sea-ice thickness that is used in the sea-ice model code to calculate >>>> heat fluxes, for example, rather than the average ice thickness that the >>>> ice would have if it were to cover the entire area of the grid cell >>>> while conserving its volume. >>>> >>>> To prevent such confusion in the future, we would like to add the >>>> following variable to the CF convention: >>>> >>>> 1. equivalent_sea_ice_thickness (new variable with units 'm3 m-2' or 'm') >>>> to describe sea-ice volume per grid-cell area >>>> >>>> The term "Equivalent sea-ice thickness" is known within the sea-ice >>>> community to refer to "sea-ice volume per grid-cell area". Ideally, we >>>> would have liked to suggest a variable name containing the term >>>> "volume", but this seems difficult within the CF convention as then >>>> units couldn't be 'm'. >>>> >>>> Thank you very much for any feedback, help and guidance. >>>> >>>> Best, >>>> >>>> Dirk Notz >>>> >>>> >>>> >>>> -- >>>> ---- >>>> Dr. Dirk Notz >>>> http://www.mpimet.mpg.de/~notz.dirk >>>> _______________________________________________ >>>> CF-metadata mailing list >>>> CF-metadata at cgd.ucar.edu >>>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>> >>> ----- End forwarded message ----- >>> _______________________________________________ >>> CF-metadata mailing list >>> CF-metadata at cgd.ucar.edu >>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >>> > > ----- End forwarded message ----- > _______________________________________________ > CF-metadata mailing list > CF-metadata at cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata >Received on Thu Jul 21 2016 - 07:35:12 BST
This archive was generated by hypermail 2.3.0 : Tue Sep 13 2022 - 23:02:42 BST