Dear Siobhan and Karl,
As far as standard names are concerned, I think we need to go ahead and
introduce two new names:
integral_of_sea_ice_temperature_wrt_depth_expressed_as_heat_content;
Jm-2
sea_ice_albedo; 1.
If a single sea_ice albedo is required and snow cover is to be diagnosed
separately, then I think we don't need to introduce the new area_type of
snow_free_sea_ice at the moment.
As far as CMIP5 output is concerned, it seems we need to re-introduce
two saved fields as follows:
OImon: Long Name: "Thermal Energy Content of Snow on Sea Ice" Standard
Name: thermal_energy_content_of_surface_snow Units: J m-2 cell_methods:
"time: mean area: mean where sea-ice" dimensions: longitude latitude
time
LImon: Long Name: "Thermal Energy Content of Snow on Land" Standard
Name: thermal_energy_content_of_surface_snow Units: J m-2 cell_methods:
"time: mean area: mean where land" dimensions: longitude latitude time
OImon row 39 needs to have the units changed to J m-2 and a standard
name of
integral_of_sea_ice_temperature_wrt_depth_expressed_as_heat_content.
For the sea_ice albedo I think we need:
OImon row 23 with a standard name of sea_ice_albedo and cell_methods:
"time: mean area: mean where sea_ice"
If any further discussion of the CMIP5 output is needed, I suggest that
we move it away from the mailing list as it isn't strictly a CF matter
now that the standard names are (hopefully) agreed.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
Rutherford Appleton Laboratory Email: alison.pamment at stfc.ac.uk
Chilton, Didcot, OX11 0QX, U.K.
> -----Original Message-----
> From: Siobhan.O'farrell at csiro.au [mailto:Siobhan.O'farrell at csiro.au]
> Sent: 29 September 2010 08:51
> To: Pamment, Alison (STFC,RAL,SSTD); taylor13 at llnl.gov
> Cc: j.m.gregory at reading.ac.uk; cf-metadata at cgd.ucar.edu
> Subject: RE: [CF-metadata] CMIP5 cryosphere standard names and
standard
> CMIP5 output
>
> HI Alison and Karl,
>
> I am happy with points 1), 2), 6), 7) and 10)
>
> The two outstanding ones are the Sea ice thermal energy and bare sea
> ice albedo, both of which are flagged for action in the CMIP5
document.
> If we can switch the thermal_energy_content_of_snow back on for both
> land and sea ice surfaces that would resolve one of the points raised
> and as I said it was there for land surface under a different name in
> an earlier version of the CMIP5 document.
>
>
> For point 9, I think the best compromise is to have one sea ice albedo
> only, which would capture the snow covered period, spring melt
> conditions and bare summer conditions as well.
>
> Best wishes
>
> Siobhan
>
> -----Original Message-----
> From: alison.pamment at stfc.ac.uk [mailto:alison.pamment at stfc.ac.uk]
> Sent: Tuesday, 28 September 2010 10:15 PM
> To: cf-metadata at cgd.ucar.edu; O'Farrell, Siobhan (CMAR, Aspendale)
> Cc: j.m.gregory at reading.ac.uk
> Subject: RE: [CF-metadata] CMIP5 cryosphere standard names
>
> Dear Jonathan and Siobhan,
>
> Thank you for your responses. Please see below for an update on the
> status of the discussions.
>
> 1) We are agreed on surface_downward_heat_flux_in_snow (Wm-2). The
> CMIP5
> output will use
> a cell_methods of "area: mean where land".
>
> This name is accepted for inclusion in the standard name table.
>
> 2) Jonathan wrote:
>
> > > (a) Long name 'Surface Temperature of Sea Ice' with units of K and
> the
> > > following explanatory comments: 'When computing the time-mean
here,
> > > the time-samples, weighted by the area of sea ice in the grid
cell,
> > > are accumulated and then divided by the sum of the weights.
Report
> as
> > > "missing" in regions free of sea ice. Note this will be the
> surface
>
> > > snow temperature in regions where snow covers the sea ice.'
> >
> > > (b) Long name 'Temperature at Interface Between Sea Ice and Snow'
> with
> > > units of K and the following explanatory comments: 'When computing
> the
> > > time-mean here, the time-samples, weighted by the area of
> snow-covered
> > > sea ice in the grid cell, are accumulated and then divided by the
> sum
> > > of the weights. Report as "missing" in regions free of snow-
> covered
>
> > > sea ice.'
> >
> > It seems to me that (a) is surface_temperature for area: where
> sea_ice, and (b) is
> > sea_ice_surface_temperature for area: where snow_on_sea_ice, in
> which
> I have invented a
> > new area_type. Both are time: mean.
>
> Siobhan wrote:
> > I think Jonathan's sub categories where snow_on_sea_ice and
> snow_free_sea_ice approach
> > helps here, we definitely want the surface temperature over the ice
> portion of the grid
> > cell rather than over the whole grid cell (using cell methods). Also
> the interface
> > temperature between snow and ice is important to account for, as it
> is
> much warmer than
> > the surface temperature due to the thermal insulation on snow so I
am
> no two worried about
> > the case when there is no snow cover but again the snow_on_sea ice
> (area type) would help to prevent the confusion.
>
> Jonathan's approach simplifies these quantities and I'm happy to
follow
> his suggestion. I think, then, that we are agreed on using the
> existing
> standard name of surface_temperature for the first quantity and
> introducing a new standard name of
> sea_ice_surface_temperature; K
> for the second.
>
> This name is accepted for inclusion in the standard name table.
>
> A new type of snow_on_sea_ice will be added to the area_type table.
>
> I will check that the CMIP5 output document contains the correct
> cell_methods entries for these quantities.
>
> (Items 3, 4 and 5 are closed).
>
> 6) Alison wrote:
>
> > I think we should use the existing standard names of
> > rainfall_flux; kg m-2 s-1
> > snowfall_flux; kg m-2 s-1
> > and supply a cell_methods attribute of "area: mean where sea_ice
over
> > sea" for each of them.
>
> Jonathan says he agrees.
>
> Siobhan wrote:
>
> > It makes sense to separate the water flux from snow and rainfall as
> the impact differently on the
> > surface using the cell methods would indicate them onto the sea ice
> portion of the cell. Some
> > rain may penetrate into the ice lattice if it s very porous Jonathan
> or contribute to melt ponds in
> > the Arctic summer, but I don't know of a sea ice models IN CMIP5
> that sophisticated to allow for
> > that effect.
>
> Sorry, Siobhan, I'm not 100 per cent clear whether you are happy to go
> with the names I suggested. The names will certainly allow you to
> separate snow and rainfall as per your requirements.
>
> 7) We are agreed on
> tendency_of_sea_ice_amount_due_to_lateral_growth_of_ice_floes; kg m-2
> s-1.
>
> This name is accepted for inclusion in the standard name table.
>
> 8) Sea ice thermal energy
>
> Jonathan wrote:
> > > sea_ice_thermal_energy; J
> > Is it really J, not J m-2? If J m-2, the phrase heat_content would
be
> > better, as it would be consistent with the existing name
>
>integral_of_sea_water_potential_temperature_wrt_depth_expressed_as_hea
> t
> _content
> > (J m-2). If really J, I wonder if we can think of a phrase related
to
> > heat_content. I am assuming that this quantity relates to
> > temperature, but maybe it relates to latent heat content? It would
be
> > good to be clear about this in the name.
> >
>
> Alison wrote:
> > According to the CMIP5 document, the unit is J and the long name is
> 'Sea
> > Ice Total Heat Content'. The explanation says, 'Ice at 0 Celsius is
> > assumed taken to have a heat content of 0 J. When averaging over
> time,
> > this quantity is weighted by the mass of sea ice. Report as
> "missing"
> > in regions free of snow on land.'
> >
> > I find this rather confusing - if it is supposed to be a sea ice
> > quantity, then surely it should always be reported as "missing" over
> > land and open sea. It doesn't sound as though latent heat is
> included.
> > I don't think we can call it a 'content' because it isn't a quantity
> per
> > unit area. Perhaps Siobhan can help to clarify this quantity
further.
>
> Siobhan wrote:
>
> > Sea ice thermal energy, I am a bit confused on the history on this
> one
> there were two
> > requests originally made in my 2008 document sent To Karl and
> circulated through the
> > cryosphere community.
> >
> > The first was
> > Snow_thermal_energy_content Snth new Jm-2 month 1
> all
> >
> > For the land surface component. It was in an earlier version of
> Karl's
> document (I had
> > saved 16/6/2009) but is not in the latest 17/9/2010.
> >
> > The sea ice heat content was given as
> >
> > integral_of_sea_ice_temperature_wrt_depth_expressed_as_heat_content
> hcice New Jm-2 Month 1 All
> >
> >
> > It looks like they retained the hcice name but changed the units.
> >
> > So I am puzzled as well, I think it should be Jm-2.
> >
> > The issue of whether the heat content of the snow over the ice
should
> be included is highlighted, it is possible,
> > but it would be preferable as separate variable, as the thermal
> properties are very different form the ice, and it
> > could confuse interpretation of result if they were merged into one
> effect (Unless you are using the UM, Jonathan
> > where the atmosphere model treats the two media as if they are
> combined).
>
> We already have the standard name
> thermal_energy_content_of_surface_snow
> (J m-2) which, if supplied with the correct cell_methods, would deal
> with the first quantity Siobhan mentions. However, I agree that it
> doesn't seem to be listed as a separate output in the 17/9/2010 CMIP5
> document. If it is needed for CMIP5, then Karl would be the person to
> contact.
>
> We seem to be in general agreement that the units of the sea_ice
> thermal
> content should be J m-2, so I will feed that information back to Karl.
> A
> quantity per unit area can certainly be called a 'content' in standard
> names, so in fact the original suggestion of
> integral_of_sea_ice_temperature_wrt_depth_expressed_as_heat_content; J
> m-2
> would be appropriate and it would fit with Jonathan's comments. Is
> this
> OK?
>
> 9) Sea ice albedo
>
> Siobhan wrote:
> > I was bothered that the bare sea ice albedo has been flagged for
> > removal, It probably should be total sea
> > ice albedo, though in NCAR model bare ice albedo is changeable due
to
> > black carbon and multi-scattering in
> > internal layers. There is a comment on the next page about getting
> > albedo from the downwelling and
> > upwelling shortwave radiation, but this would not allow for the
> > penetration of shortwave radiation into the
> > ice. My preference is for total sea ice albedo to be saved. This
> will
> > allows for the more sophisticate
> > schemes to have an areal average of seasonal changes in albedos
> across
> > thickness categories, snow cover
> > properties, melt ponds and now aerosols effects to be analyzed, I
> > couldn't find surface albedo being
> > saved elsewhere in the CMIP5 document.
>
> Alison wrote:
> > In view of Siobhan's comments I think there is definitely a need to
> > agree a name for this quantity. I think that Karl is correct that
> > 'surface_albedo' would normally refer to the whole grid cell. It
> should
> > really be 'sea_ice_albedo'. We could introduce a new name of
> > 'sea_ice_albedo_assuming_no_snow' but I'm not sure whether it is
> really
> > correct to use the "assuming" phrase here. Perhaps it would be more
> > accurate to use the existing name 'sea_ice_albedo' and introduce a
> new
> > area_type of 'snow_free_ice'. I'd welcome opinions on this.
>
> Jonathan wrote:
>
> > I think that would be a correct description, yes. This area-type is
> the counterpart of
> > snow_on_sea_ice which I needed above. I think yours should be
> snow_free_sea_ice.
>
> Siobhan wrote:
>
> > I still support the need for a sea ice albedos, my comments on
> whether
> it is total or bare
> > still stand, again it should be defined on the sea ice portion of
the
> grid. Alison's
> > suggestion of an area type snow_free_ice could help distinguish it
is
> bare, but if the snow
> > depth is also known, then that would be clearer, though there will
be
> transition months as
> > the ice becomes snow free.
> >
> > So is one total sea ice albedo sufficient?
>
> One CF standard name for sea ice albedo is sufficient if it is
> essentially the same geophysical quantity for snow covered/bare sea
> ice.
> Then the only issue is to distinguish between surface types and this
is
> the role of the area_types. Area types of snow_free_sea_ice and
> snow_on_sea_ice would allow you to make that distinction, so I am in
> favour of introducing one new standard name of sea_ice_albedo, plus
the
> new area_types.
>
> Again regarding CMIP5, Karl would be the person to contact if you wish
> to save the albedo for both surface types as currently only the bare
> ice
> quantity is listed in the output document. The quantity
> surface_snow_thickness is listed as an output with a cell_methods of
> 'mean where sea'. If you wanted the same quantity saved with a
> cell_methods of 'mean where sea_ice' then I think it would be a
> separate
> output. In practice, would the quantity that is already being saved
be
> enough to tell you whether the ice is bare?
>
> 10) We are agreed to use the existing names
> surface_downward_x_stress; Pa
> surface_downward_y_stress; Pa
> and introduce two new standard names
> upward_x_stress_at_sea_ice_base; Pa
> upward_y_stress_at_sea_ice_base; Pa
> (all accompanied by a cell_methods attribute of "area: mean where
> sea_ice" for CMIP5.)
>
> The new names are accepted for inclusion in the standard name table.
>
> Best wishes,
> Alison
>
> ------
> Alison Pamment Tel: +44 1235 778065
> NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
> Rutherford Appleton Laboratory Email:
> alison.pamment at stfc.ac.uk
> Chilton, Didcot, OX11 0QX, U.K.
> --
> Scanned by iCritical.
--
Scanned by iCritical.
Received on Thu Sep 30 2010 - 04:49:30 BST
