[CF-metadata] new named fields for ocean

[Stephen Griffies]

Karl,

Here are some modifications in response to your email.

1/ As Jonathan says in his email, the desire is to have a measure of the 
total pressure applied to the liquid ocean surface, including sea ice 
and atmosphere loading.  If "surface" is interpreted as the liquid ocean 
surface, then the name surface_sea_water_pressure is fine.  But to be 
extra clear, your suggestion pressure_at_the_sea_water_surface is 
appealing.  Likewise, I suggest changing sea_water_pressure_at_sea_floor 
to just the simpler  pressure_at_sea_floor, since the desired pressure 
includes that from seawater as well as the media above the liquid ocean. 

In summary, I recommend the following two field names that are 
sufficient to bound the ocean pressure field:

pressure_at_the_sea_water_surface
pressure_at_sea_floor

2/ There is presently no minimum set of grid variables discussed in the 
report.  The resolution of what is a minimal set goes beyond this email 
list.  But in the process of thinking about this set, it is important to 
remember that the vertical thickness and mass per unit area are in 
general time dependent three dimensional fields. 

3/ For age, I concur with Jonathan, and recommend age to be in years, 
and will discuss this point in the report more clearly.

4/ There are multiple mixed layers already defined in CF.  Mixed layer 
as defined by a density criteria (e.g., as in Levitus) is distinct from 
the depth that turbulent mixing occurs.  There are physical reasons to 
request BOTH. We detail why in the ocean report.


5/ temperature flux question: 
>
> I do not like "temperature flux" expressed as heat flux.  There must 
> be some terms used in engineering and physics that are better for 
> this. Ablation of material surfaces remove energy both by removing 
> mass with a certain amount of internal energy and by energy required 
> to change the phase.  Is anyone familiar with the terminology?
>

I too find this name unappealing.  I suggest the following alternatives: 

temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_sea_water   
--> heat_flux_into_sea_water_due_to_rainfall_mass_flux

temperature_flux_due_to_evaporation_expressed_as_heat_flux_out_of_sea_water 
--> heat_flux_out_of_sea_water_due_to_evaporative_mass_flux

temperature_flux_due_to_runoff_expressed_as_heat_flux_into_sea_water --> 
heat_flux_into_sea_water_due_to_runoff_mass_flux

These new names are A/ shorter, B/ more directly what is intended 
physically; i.e., a heat flux due to a mass flux.

6/ snowfall question:

> Also, are you sure you want only "rainfall", rather than 
> "precipitation" , which includes water falling out of the atmosphere 
> in the solid state (e.g., snow). Perhaps you need to "snowfall" 
> besides "rainfall" (because the snow likely melts when it hits the 
> ocean with the resultant latent heat transfer), but I didn't see 
> mention of "snow" on the list.
>

Good point.  We do request snowfall as a mass flux. But since we are 
measuring heat flux from mass transfer, relative to 0C, then snow 
falling at 0C will not contribute any heat transfer due to mass 
transfer. But as you say, it will cause heat transfer from latent heat 
of fusion. This latent heat term was missing in our original report.  
For this latent heat, I suggest  the name

heat_flux_into_sea_water_due_to_snow_thermodynamics

analogous to the other fields of this sort from icebergs and seaice. 


Best,
 Stephen

-- 
Stephen M. Griffies                    phone: +1-609-452-6672
Geophysical Fluid Dynamics Laboratory  FAX:   +1-609-987-5063
Princeton Forrestal Campus Rte. 1      email: stephen.griffies at noaa.gov
201 Forrestal Road                     http://www.gfdl.noaa.gov/~smg
Princeton, NJ 08542-0308  USA