[CF-metadata] CMIP5 cryosphere standard names

From: Jonathan Gregory <j.m.gregory>
Date: Fri, 24 Sep 2010 19:57:46 +0100

Dear Alison

> Therefore, I think we
> should introduce a new standard name of
> surface_downward_heat_flux_in_snow (Wm-2). The CMIP5 output can then use
> a cell_methods of "area: mean where land". OK?

I agree.

> (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.

> 6. Water flux names
>
> 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. Does that seem more sensible?

Yes, I agree. That seems to be exactly what the CMIP5 description says. Thanks.

> 8. Sea ice thermal energy
>
> 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.

It is unusual to report a quantity extensive in area, isn't it. Things are
usually intensive i.e. m-2.

> 9. Bare Sea Ice Albedo
>
> 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 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.

> 10. X and y components of stress on sea ice surface and base
> We already have existing names
> surface_downward_x_stress; Pa
> surface_downward_y_stress; Pa
> which we can use for the first two quantities.
>
> I now propose that we introduce two new standard names
> upward_x_stress_at_sea_ice_base; Pa
> upward_y_stress_at_sea_ice_base; Pa.
>
> I think also that for CMIP5 these four quantities should be accompanied
> by a cell_methods attribute of "area: mean where sea_ice".
>
> Is this OK?

I would say so, yes.

Best wishes

Jonathan
Received on Fri Sep 24 2010 - 12:57:46 BST