Hi Roy,
Thank you for your thoughtful response. In my personal ontology world view, the CF standard names occupy a unique niche. Standard names combined with canonical units (for example 'dew_point_temperature in K') are more concise than BODC parameter groups or GCMD categories (for example 'Atmospheric humidity'), yet less concise than BODC parameter names (3 different definitions for Dew Point Temperature). The standard names allow a user to quickly find and group mathematically comparable information together, perhaps using more concise variable names to further refine the selection. However, the CF standard names have quite a few gaps, which is why I have proposed these names.
Perhaps the standard name gaps pertinent to observational oceanography are appropriate in a 'climate forecast' metadata standard. If people want to discuss a separate list of observational oceanography names at the 'standard name' level of succinctness (with canonical units), I'd certainly be happy to participate in that discussion.
OK, now on to your questions:
> Shouldn't pCO2 for a 'standard name' (ie a name put up for interoperability) be atmospheric pressure corrected and therefore have actual units of micro-atmosheres (rather than ppm), giving canonical units of Pa?
Yes, that makes perfect sense.
> There is already 'downwelling_photon_spherical_irradiance_in_sea_water' to describe 2-pi scalar irradiance. Would it be best to continue to use 'spherical' rather than 'scalar' for your term? If not, should we be introducing aliases?
By using the word 'scalar' in the variable name, I was trying to indicate that this was 4-pi irradiance, rather than 2-pi irradiance. Given the alias-like nature of 'scalar' and 'spherical', maybe this is not the best technique. How about '(photon|photosynthetic|spectral)_total_spherical_irradiance_in_sea_water', using the word 'total' to indicate 4-pi irradiance?
>platform_heading needs clarification. If the platform is a ship, heading can either be interpreted as the direction towards which the bow is pointing or the direction towards which the ship is travelling (very different if going backwards!).
Yes, I see... And a spacecraft's velocity vector could be completely unrelated to the direction it is facing. I suppose that heading is therefore a homonym for either the direction one is facing or the direction one is moving. Since in this case I am concerned about the direction the platform is facing, perhaps a better variable name is 'platform_forward_looking_direction'?
> Is 'sea_water_acoustic_velocity' the velocity of sound in sea water. If so, my guess is it should be phrased differently.
Yes, and on second thought, using the term 'velocity' is probably inappropriate since sound is characterized by a scalar: the speed of sound waves in a material, independent of direction. How about 'speed_of_sound_in_seawater' or 'seawater_speed_of_sound'?
>Canonical units for bioluminescence - mol s-1?
I agree.
>Why use 'concentration' for oxygen and 'molality' for nutrients?
My mistake. It should be 'molality' for both. Especially since 'oxygen_concentration' is most commonly expressed in kg m-3.
>The term 'fluorescence' is one of my nightmares. Even the definition given doesn't tell the whole story. Do we need to include excitation and measurement wavelengths as we're now starting to encounter fluorometers designed to measure phycoerythrin as well as chlorophyll?
I agree with both of your sentiments. And yes, I think that one really needs to specify the excitation and measurement wavelengths (either as a separate variable or in the long name). I'd like to use 'chlorophyll_concentration_in_sea_water', but most scientists don't bother to calibrate their fluorometers to chlorophyll concentrations, and just use relative fluorometer outputs to characterize differences. My definiton relates to a specific instrument, but even then, the water volume being sampled is not specified, and all the excited photons are not being collected, so the values are scientifically as useful as 'counts'. Perhaps 'chlorophyll_fluorescence' as you suggest (with no units) is the best compromise? But that probably kills interoperability. A nightmare indeed.
> The optics parameters do not include any information on the light wavelength to which they pertain. We have attenuation data from red and green light transmissometers and I know of blue light instruments. There is also the developing minefield of whether attenuation is relative to air or to pure water (clear water value is zero in latter case).
I think this needs to be handled like the 'downwelling_spectral' class of variables -- with either a separate variable (or dimension) that indicates wavelength, or with an indication in the variable long name. Good point about 'relative to'. Since one can (and ocasionally does) measure the attenuation of pure water, I think the variable should be relative to air.
>I'm not clear about the difference between 'sea_water_particulate_volume_scattering_function' and 'sea_water_volume_scattering_function'. I think definitions would be helpful here.
Once again, this was my mistake. I should have removed the 'particulate' variables from the list. The 'particulate' distinction probably belongs in the long variable name, which would also specify the particulate size range.
Regards,
Mike
-----Original Message-----
From: cf-metadata-bounces at cgd.ucar.edu [mailto:cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Roy Lowry
Sent: Tuesday, July 26, 2005 1:27 AM
To: cf-metadata at cgd.ucar.edu; Godin at mbari.org
Subject: Re: [CF-metadata] Proposed Standard Names
Hi Michael,
Besides my expected general concern of increasing the overlap of the CF standard names into the domain of observational oceanography further increasing future interoperability problems (requiring more mapping/ontology building work), I have some specific comments:
Shouldn't pCO2 for a 'standard name' (ie a name put up for interoperability) be atmospheric pressure corrected and therefore have actual units of micro-atmosheres (rather than ppm), giving canonical units of Pa?
There is already 'downwelling_photon_spherical_irradiance_in_sea_water' to describe 2-pi scalar irradiance. Would it be best to continue to use 'spherical' rather than 'scalar' for your term? If not, should we be introducing aliases?
platform_heading needs clarification. If the platform is a ship, heading can either be interpreted as the direction towards which the bow is pointing or the direction towards which the ship is travelling (very different if going backwards!).
Is 'sea_water_acoustic_velocity' the velocity of sound in sea water. If so, my guess is it should be phrased differently.
Canonical units for bioluminescence - mol s-1?
Why use 'concentration' for oxygen and 'molality' for nutrients?
The term 'fluorescence' is one of my nightmares. Even the definition given doesn't tell the whole story. Do we need to include excitation and measurement wavelengths as we're now starting to encounter fluorometers designed to measure phycoerythrin as well as chlorophyll? Using the term 'chlorophyll_fluorescence' might address this.
However, we've received data labelled 'fluorescence' that have been:
Fluorometer output in counts
Fluorometer output in volts
Processed fluorometer output voltage resulting in a nominal chlorophyll concentration
but never received data that correspond to the definition given. This makes me curious as to what it is you actually have in this channel: might be worth checking.
The optics parameters do not include any information on the light wavelength to which they pertain. We have attenuation data from red and green light transmissometers and I know of blue light instruments. There is also the developing minefield of whether attenuation is relative to air or to pure water (clear water value is zero in latter case). I assume that 'transmissivity' is the proportion of light transmitted that is received. If this is the case it either needs normalising to 1m path length (making canonical units m-1, not 1) or information on the path-length incorporated.
I'm not clear about the difference between 'sea_water_particulate_volume_scattering_function' and 'sea_water_volume_scattering_function'. I think definitions would be helpful here.
Most (but not all) of these parameters are covered by the BODC parameter usage vocabulary. I really think that finding a way of utilising this resource within the CF convention framework would save us a lot of unnecessary work in the future.
Cheers, Roy.
>>> "Godin, Michael" <Godin at mbari.org> 7/25/2005 10:13:16 pm >>>
I'd like to propose some names I had to create while handling a pretty diverse set of oceanographic (and ancillary) data. I am rather certain that these names do not already exist in the database, but I am less certain if I have followed the naming convention well.
The proposed names and units follow here:
air_carbon_dioxide_partial_pressure, 1
altitude_above_seafloor, m
photosynthetic_scalar_irradiance_in_sea_water, W m-3
platform_heading, degree
platform_pitch, degree
platform_roll, degree
platform_speed, m s-1
sea_water_acoustic_velocity, m s-1
sea_water_bioluminescence, photon s-1
sea_water_carbon_dioxide_partial_pressure, 1
sea_water_dissolved_oxygen_concentration, mol kg-1
sea_water_dissolved_oxygen_saturation, 1
sea_water_dissolved_oxygen_volume_fraction, 1
sea_water_fluorescence, 1
sea_water_nitrate_molality, mol kg-1
sea_water_optical_absorption, m-1
sea_water_optical_attenuation, m-1
sea_water_optical_backscatter, m-1
sea_water_optical_transmissivity, 1
sea_water_particulate_optical_backscatter, m-1
sea_water_particulate_volume_scattering_function, m-1 sr-1
sea_water_phosphate_molality, mol kg-1
sea_water_silicate_molality, mol kg-1
sea_water_volume_scattering_function, m-1 sr-1
spectral_scalar_irradiance_in_sea_water, W m-3
surface_carbon_dioxide_partial_pressure_anomaly, 1
water_flow_rate, m3 s-1
A few may require some explanation:
photosynthetic_scalar_irradiance_in_sea_water: Sum of radiation from all directions. "Photosynthetic" radiation is the part of the spectrum which is used in photosynthesis e.g. 300-700 nm. The range of wavelengths could be specified precisely by the bounds of a coordinate of radiation_wavelength. Scalar irradiance is the photon flux incident on unit area of a spherical (or "4-pi") collector.
sea_water_bioluminescence: Number of photons emitted from bioluminescent organisms in 1 ml of sea water, at a given flow rate.
sea_water_fluorescence: Fraction of light returned from sea water, relative t to illumination level.
spectral_scalar_irradiance_in_sea_water: Sum of radiation from all directions. "spectral" means per unit wavelength or as a function of wavelength; spectral quantities are sometimes called "monochromatic". Scalar irradiance is the photon flux incident on unit area of a spherical (or "4-pi") collector.
Thanks, Mike
_____________________________________________
Michael A. Godin
Software Engineer
Monterey Bay Aquarium Research Institute
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Received on Tue Jul 26 2005 - 12:50:34 BST
