Implentation of absolute pressure in the Argo data system

[JohnEGilson]

The Argo data system has no present method to report a pressure sensor that reports absolute pressure. PRES is sea_water_pressure (e.g. 0 at the surface). I'm requesting modification of the NVS tables to allow for absolute pressure.

Background: 12 of our Deep SOLO have a secondary pressure sensor manufacturerd by Quartzdyne that reports absolute pressure (dbar). This is NOT the sensor within the CTD.

For this purpose I'd suggest adding a new ocean state variable,

(R03) PARAMETER = ABS_PRES
float ABS_PRES(N_PROF, N_LEVELS) ;
ABS_PRES:long_name = "Absolute pressure" ;
ABS_PRES:standard_name = "absolute_pressure" ;
Looking here https://cfconventions.org/Data/cf-standard-names/current/build/cf-standard-name-table.html
I see that 'sea_water_pressure' is CF for the absolute pressure (water + air). But Argo uses 'sea_water_pressure' for water only (the document lists for this use 'sea_water_pressure_due_to_sea_water'
If other names are better than ABS_PRES please advise.

In terms of the other NVS tables...Sensor Maker and model are already defined.
R25 : Would CTD_PRES remain appropriate for absolute pressure? Or would R25 need a new definition?

Units: In the case of the Deep SOLO, the Quartzdyne returns the pressure in dbar. Keeping the units in dbar would be my preference. However, do others believe mandating a different unit would be beneficial to differentiate Argo sea_water_pressure and absolute pressure (e.g. psi)

[apswong]

More information is needed to assess this request under the category of "new sensor for an existing approved parameter".

1. Is this secondary Quartzdyne pressure sensor an "experimental" sensor? If it is in the "experimental" phase, then its data are to be stored in the aux directory, and so no new NVS vocab is needed.

2. If this secondary Quartzdyne pressure sensor is progressing from the "experimental" phase to the "pilot" phase, then we need to better understand the relationship between the absolute pressure that it reports, and PRES. If absolute pressure is used to compute PRES, then the new NVS vocab will be an intermediate parameter, not an ocean state parameter.

3. Absolute pressure is usually reported in psi. If the secondary Quartzdyne pressure sensor reports this data in dbar, then the data may not be true absolute pressure, but some variant of absolute pressure. An alternative name may be needed to reflect this variant.