[CF-metadata] New standard names for NEMO ocean model output

Sebastien Villaume sebastien.villaume at ecmwf.int
Tue Apr 18 02:20:21 MDT 2017


Dear Alison,

The new standard names you are suggesting for (3), (4) and (5) are interesting. 

I have few comments:

when I searched "sea_surface_height" in the latest standard name table, I noticed standard names with "sea_surface_height_amplitude_due_to", "sea_surface_height_bias_due_to", and "sea_surface_height_correction_due_to". would it make sense to use "sea_surface_height_change_due_to" or "due_to" is only reserved for certain cases (like external physical processes)?

I am also wondering if the reference "above_X" for the height is needed: the change in height will be the same whatever the origin chosen (sea floor, geoid, etc.) because it is the difference between 2 heights sharing the same reference. In that sense it feels that "steric_change_in_sea_surface_height", "halosteric_change_in_sea_surface_height" and "thermosteric_change_in_sea_surface_height" are enough.

Best wishes,
/Sébastien

----- Original Message -----
From: "alison pamment" <alison.pamment at stfc.ac.uk>
To: "sebastien villaume" <sebastien.villaume at ecmwf.int>, cf-metadata at cgd.ucar.edu
Sent: Thursday, 13 April, 2017 17:41:38
Subject: RE: New standard names for NEMO ocean model output

Dear Jonathan and Sebastien,

Thank you both for your comments. I think we are now agreed on the following names (with definitions as given in my previous email http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2017/059392.html):

1. sea_water_mass_per_unit_area_expressed_as_thickness (m)
2. ocean_mixed_layer_thickness_defined_by_vertical_tracer_diffusivity_threshold (m)
2a. The existing name ocean_mixed_layer_thickness_defined_by_vertical_tracer_diffusivity will become an alias of ocean_mixed_layer_thickness_defined_by_vertical_tracer_diffusivity_deficit (m).
6. ratio_of_sea_water_potential_temperature_anomaly_to_relaxation_timescale (K s-1)
7. ratio_of_sea_water_practical_salinity_anomaly_to_relaxation_timescale (s-1)
8. integral_of_sea_water_practical_salinity_wrt_depth (m)

These names are accepted for publication in the standard name table and will be added at the next update, scheduled for 24th April.

I think we have also agreed to drop proposal (9) integral_of_sea_water_practical_salinity_wrt_total_depth (m) because it is the same quantity as (8).

For the 'steric' names, Jonathan feels these should indicate that the term relates to a change in local sea level, rather than simply water column thickness, and Sebastien is keen that we adopt a common approach for all three names. We have a number of "sea_surface_height_above_X" names where X is variously "geoid", "reference_ellipsoid", etc. Based on this syntax I would then suggest the following names:

3. steric_change_in_sea_surface_height_above_sea_floor (m)
' "Sea surface height" is a time-varying quantity. The steric change in sea surface height is the change in height a water column of standard temperature T=0°C and practical salinity S=35.0 would undergo when its temperature and salinity are changed to the observed values. The sum of the quantities with standard names thermosteric_change_in_sea_surface_height_above_sea_floor and halosteric_change_in_sea_surface_height_above_sea_floor is the total steric change in the water column height, which has the standard name of steric_change_in_sea_surface_height_above_sea_floor. The sum of the quantities with standard names sea_water_mass_per_unit_area_expressed_as_thickness and steric_change_in_sea_surface_height_above_sea_floor is the total thickness of the sea water column.'

4. halosteric_change_in_sea_surface_height_above_sea_floor (m)
' "Sea surface height" is a time-varying quantity. The halosteric change in sea surface height is the change in height a water column of standard practical salinity S=35.0 would undergo when its salinity is changed to the observed value. The sum of the quantities with standard names thermosteric_change_in_sea_surface_height_above_sea_floor and halosteric_change_in_sea_surface_height_above_sea_floor is the total steric change in the water column height, which has the standard name of steric_change_in_sea_surface_height_above_sea_floor.'

5. thermosteric_change_in_sea_surface_height_above_sea_floor (m)
' "Sea surface height" is a time-varying quantity. The thermosteric change in sea surface height is the change in height a water column of standard temperature T=0°C would undergo when its temperature is changed to the observed value. The sum of the quantities with standard names thermosteric_change_in_sea_surface_height_above_sea_floor and halosteric_change_in_sea_surface_height_above_sea_floor is the total steric change in the water column height, which has the standard name of steric_change_in_sea_surface_height_above_sea_floor.'

Are these better?

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: CF-metadata [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of
> Sebastien Villaume
> Sent: 05 April 2017 11:51
> To: cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] New standard names for NEMO ocean model output
> 
> 
> Dear Alison et al,
> 
> we are happy with your suggestions/modifications.
> 
> I also understand from your comments to
> integral_of_sea_water_practical_salinity_wrt_depth that my proposal to
> rename
> integral_of_sea_water_potential_temperature_wrt_depth_expressed_as_heat_
> content for consistency is no longer required.
> 
> 
> Regarding Jonathan comments, I think we (Eric, Kevin, myself) are fine with
> "thickness", "thickness_change", "height" or "height_change" for the steric,
> halosteric and thermosteric contributions as long as it is consistent for the
> three standard names and other related names.
> 
> In the future, we may want to produce the steric, halosteric and thermosteric
> contributions of each water cell of the column, not only for the whole water
> column. The definitions of the present standard names and the possibility to
> derive new standard names for this future situation need to be taken into
> account.
> 
> one more question: what is the standard name corresponding to
> sea_water_mass_per_unit_area_expressed_as_thickness (at 0degC, 35psu) +
> ocean_steric_thickness? i.e the total thickness of the water column? it is not
> clear to me if it exists or if we should use
> sea_water_mass_per_unit_area_expressed_as_thickness and point to an
> auxiliary variable sea_water_density at XdegC and Ypsu...
> 
> thanks,
> Sebastien
> 
> ____________________________________
> 
> Dr. Sébastien Villaume
> Analyst
> ECMWF Shinfield Park,
> Reading RG2 9AX, UK
> +44 7825 521592
> sebastien.villaume at ecmwf.int
> ____________________________________
> 
> ----- Original Message -----
> From: "Jonathan Gregory" <j.m.gregory at reading.ac.uk>
> To: cf-metadata at cgd.ucar.edu
> Sent: Tuesday, 4 April, 2017 21:13:08
> Subject: Re: [CF-metadata] New standard names for NEMO ocean model output
> 
> Dear Alison
> 
> Thank you for your careful and sensible analysis, as always. I agree with all
> your proposals except that I'm sorry to say I'm not happy about the steric
> height yet. I don't seek to insist on what I suggested before, but I don't
> think the proposal so far matches scientific terminology as far as I'm aware.
> 
> > 3. ocean_steric_thickness (m)
> > 4. ocean_halosteric_thickness (m)
> > 5. ocean_thermosteric_thickness (m)
> 
> I understand these to mean the *change* in the thickness of the water column
> caused by change to sea water density, due to change in T and S. That's what
> your definitions indicate. If it's a change in thickness, it's confusing to
> call it a thickness, I would say. People often refer to quantities of "steric/
> halosteric/thermosteric sea level change", which I think are the same as what
> we're talking about here. The change in thickness of the water column (the
> vertical distance from the sea floor to the sea surface) is of course the same
> thing as local sea level change.
> 
> Best wishes
> 
> Jonathan
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