Dear All,
I have received via email a comment that the units of the proposed
standard name compressive_strength_of_sea_ice should be Pa m rather than
simply Pa. Siobhan has confirmed that this is correct so I will amend
the units. Apart from this I have received no further comments on the
cryosphere names since 29th July. Therefore, the following names are
now accepted for inclusion in the standard name table:
heat_flux_into_sea_water_due_to_freezing_of_frazil_ice; Wm-2
age_of_surface_snow; day
permafrost_layer_thickness; m
liquid_water_content_of_permafrost_layer; kg m-2
sea_ice_and_surface_snow_amount; kg m-2
sea_ice_salinity; psu
water_flux_into_sea_ice_from_rain; kg m-2 s-1
water_flux_into_sea_ice_from_snow; kg m-2 s-1
age_of_sea_ice; year
tendency_of_sea_ice_amount_due_to_frazil_ice_accumulation_in_leads; kg
m-2 s-1
tendency_of_sea_ice_amount_due_to_congelation_ice_accumulation; kg m-2
s-1
tendency_of_sea_ice_amount_due_to_lateral_growth_of_ice_sheet; kg m-2
s-1
tendency_of_sea_ice_amount_due_to_snow_conversion; kg m-2 s-1
tendency_of_surface_snow_melt_amount; kg m-2 s-1
tendency_of_sea_ice_amount_due_to_surface_melting; kg m-2 s-1
tendency_of_sea_ice_amount_due_to_basal_melting; kg m-2 s-1
sea_ice_thermal_energy; J
sea_ice_x_transport; kg s-1
sea_ice_y_transport; kg s-1
compressive_strength_of_sea_ice; Pa m
shear_of_sea_ice_velocity; s-1
sea_water_transport_across_line; kg s-1
There is still an open question regarding the sea ice ridging quantity:
>
> I was not certain of the meaning of the quantity with long name "Sea
Ice Ridging Rate" but suggested
> tendency_of_fractional_ice_thickness_growth_due_to_ridging (s-1).
> Siobhan wrote:
> > For the ice ridging there could be two options either define it as
the
> > rate of ice volume ridged or the rate of ice area change contained
in the new ridges.
> > We may need to discuss this one further.
>
> The units of this quantity are s-1, not m3 s-1 or m2 s-1 so presumably
we are talking about a fractional change in volume or area?
> I.e. fractional or percentage increase of the ice volume|area that
already existed?
>
> Perhaps the name should be
> tendency_of_fractional_growth_in_ice_volume_due_to_ridging or
tendency_of_fractional_growth_in_ice_area_due_to_ridging.
>
> I think we need to call the quantity a tendency because that is the
term we normally use in standard names to mean the time rate of change.
>
Looking through the list of cryosphere names again I have some
questions/comments about a few of the other proposed quantities:
1. surface_downward_heat_flux_in_snow; Wm-2
This quantity has the CMIP5 standard name of 'Downward Heat Flux into
Snow Where Land over Land' and is accompanied by the following
explanation:
'Compute the net downward heat flux from the atmosphere into the snow
that lies on land divided by the land area in the grid cell; report as
0.0 for snow-free land regions or where the land fraction is 0.' The
explanation seems to indicate that we are talking about the heat flux at
the interface between atmosphere and snow.
We already have the standard name surface_downward_heat_flux_in_air
which is defined as follows: 'The surface called "surface" means the
lower boundary of the atmosphere. "Downward" indicates a vector
component which is positive when directed downward (negative upward).
The vertical heat flux in air is the sum of all heat fluxes i.e.
radiative, latent and sensible. In accordance with common usage in
geophysical disciplines, "flux" implies per unit area, called "flux
density" in physics.' I think this is actually the same quantity, which
means that we wouldn't need to introduce a new name for snow surface
heat flux. The 'Snow Where Land over Land' part of the CMIP5 definition
belongs in the cell_methods attribute so it doesn't necessitate a new
standard name. I think, however, that we will need to introduce a new
entry of land_snow (similar to land_ice) into the area_type table.
It is true that we also have an existing standard name
surface_downward_heat_flux_in_sea_water. However, in previous
discussions of surface sea water quantities we have established that
these names generally refer to the top level of the ocean model rather
than the actual interface between atmosphere and ocean. If
surface_downward_heat_flux_in_snow refers to a layer in a snow model
then perhaps we do need a separate name, but if it refers to the
atmosphere/snow interface then I think we don't.
2. sea_ice_surface_temperature; K
The CMIP5 long_name for this quantity is 'Temperature at Interface
Between Sea Ice and Snow'. I would like to amend my suggestion for this
name to be temperature_at_interface_between_sea_ice_and_snow which I
think makes the meaning clearer and far less likely to be confused with
sea ice temperature at the interface with the atmosphere (which is just
surface_temperature).
3. sea_ice_transport OR sea_ice_transport_across_line; kg s-1
The CMIP5 output document asks for 'Sea Ice Mass Transport Through Fram
Strait'. We already have the standard name
sea_ice_transport_across_line defined as 'Transport across_line means
that which crosses a particular line on the Earth's surface; formally
this means the integral along the line of the normal component of the
transport.' I am not sure how the Fram Strait transport is defined - is
it calculated along a notional line or do we need a more general
quantity?
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: Pamment, Alison (STFC,RAL,SSTD)
> Sent: 29 July 2010 10:35
> To: CF-metadata (cf-metadata at cgd.ucar.edu)
> Cc: Siobhan.O'farrell at csiro.au
> Subject: RE: [CF-metadata] CMIP5 cryosphere standard names
>
> Dear All,
>
> I have received some comments via email from Siobhan regarding the
> CMIP5 sea-ice names. I understand that Siobhan is happy with the
> majority of the proposed names and she has made some comments
regarding
> the last three names on the list.
>
> I proposed
> divergence_of_sea_ice_velocity (already in table) or a new name of
> divergence_of_sea_ice_velocity_due_to_surface_and_basal_stresses.
> Siobhan has indicated that she prefers the first option, so we would
> not need a new name for this quantity.
>
> I proposed
> shear_of_sea_ice_velocity or
> shear_of_sea_ice_velocity_due_to_surface_and_basal_stresses.
> Again, Siobhan has indicated that she prefers the first option.
>
> The reason for not mentioning the surface and basal stresses in these
> two names is that there are also internal stresses within the ice
which
> would be included in the quantities.
>
> I was not certain of the meaning of the quantity with long name "Sea
> Ice Ridging Rate" but suggested
> tendency_of_fractional_ice_thickness_growth_due_to_ridging (s-1).
> Siobhan wrote:
> > For the ice ridging there could be two options either define it as
> the rate of ice volume
> > ridged or the rate of ice area change contained in the new ridges.
> > We may need to discuss this one further.
>
> The units of this quantity are s-1, not m3 s-1 or m2 s-1 so presumably
> we are talking about a fractional change in volume or area? I.e.
> fractional or percentage increase of the ice volume|area that already
> existed?
>
> Perhaps the name should be
> tendency_of_fractional_growth_in_ice_volume_due_to_ridging or
> tendency_of_fractional_growth_in_ice_area_due_to_ridging.
>
> I think we need to call the quantity a tendency because that is the
> term we normally use in standard names to mean the time rate of
change.
>
> I have received no other comments regarding the sea ice names. If
none
> are received by August 10th (when I return from annual leave) the
names
> (apart from the ridging name) will be accepted for inclusion in the
> standard name table.
>
> Best wishes,
> Alison
--
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Received on Mon Sep 13 2010 - 02:06:30 BST
