Hi Upendra,
It comes down to the significance of the difference between parameters according to tha application for which they are used. There ae two temperature scales - IPTS68 and ITS90. However, pragamatically for the period of time when IPTS68 was used the measurement uncertaintyfor sea temperature was significantly greater than the difference between the two scales. Assuming that sea temperature = ITS90 worked in practice (I hope everybody remembered to convert their post-90 high accuracy data to IPTS68 prior to input to the PSS78 algorithms:-)).
According to the expert carbonate system chemists, the difference between the pH scales is critical to their science - talk to the guys at CDIAC for more information. Hence the conclusion from the 2009 discussion.
Cheers, Roy.
________________________________
From: cf-metadata-bounces at cgd.ucar.edu [cf-metadata-bounces at cgd.ucar.edu] On Behalf Of Upendra Dadi [Upendra.Dadi at noaa.gov]
Sent: 09 December 2011 15:58
To: cf-metadata at cgd.ucar.edu
Subject: Re: [CF-metadata] standard name for sea water ph without
Thank you Jonathan and John for your emails.
I went through your earlier emails. One of the things that occurred to me is that these discussions that you had are as much a part of the standard as the names themselves. I think it would be great if there is better "connection" between your email conversation and the standard name tables. Often the short summary given in the standard name table, while useful, is not sufficient to understand what the name stands for.
Coming to the problem of coming up with a standard name for pH accurately, I can see the issue here. Though I am still not sure why not all five standard names were included. If there is an analogy between sea water pH and sea water temperature, as mentioned in one of the emails, why not have sea_water_pH just as we have sea_water_temperature?
Upendra
On 12/8/2011 1:39 PM, John Graybeal wrote:
Hi Upendra,
The reason the "reporting scale" is attached to this name is that the fundamental measurement, or property, to which it refers produces numbers that are not comparable to pH derived using other techniques. (They are actually measuring different quantities, not just a different offset/scale value.)
>From what I (not a scientist!) understand, it is often the case that pH that doesn't mention its scale has been measured in a way that is not an effective indicator of pH in sea water. So it is very important to understand the way the pH was measured, in order that the values be reported compatibly with others.
I am not knowledgeable enough to know the right answer to your two questions, but the above may be useful input.
John
On Dec 8, 2011, at 08:35, Upendra Dadi wrote:
Hi All,
The standard name table has an entry called "sea_water_ph_reported_on_total_scale". I have some data which does not mention the scale used for the measurement of ph. Should there be an another entry which does not mention the scale? Most of the standard names I have seen doesn't mention the scale used. Is it common to attach within standard name, the scale used for the measurement?
Upendra
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