About uncertainties in practical salinity calculations
In the current state of the art, salinity is a quantity computed from conductivity ratio measurements, with temperature and pressure known at the time of the measurement, and using the Practical Salinity Scale algorithm of 1978 (PSS-78). This calculation gives practical salinity values <I&...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2011-10-01
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| Series: | Ocean Science |
| Online Access: | http://www.ocean-sci.net/7/651/2011/os-7-651-2011.pdf |
| _version_ | 1811327785301442560 |
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| author | M. Le Menn |
| author_facet | M. Le Menn |
| author_sort | M. Le Menn |
| collection | DOAJ |
| description | In the current state of the art, salinity is a quantity computed from conductivity ratio measurements, with temperature and pressure known at the time of the measurement, and using the Practical Salinity Scale algorithm of 1978 (PSS-78). This calculation gives practical salinity values <I>S</I>. The uncertainty expected in PSS-78 values is ±0.002, but no details have ever been given on the method used to work out this uncertainty, and the error sources to include in this calculation. Following a guide published by the Bureau International des Poids et Mesures (BIPM), using two independent methods, this paper assesses the uncertainties of salinity values obtained from a laboratory salinometer and Conductivity-Temperature-Depth (CTD) measurements after laboratory calibration of a conductivity cell. The results show that the part due to the PSS-78 relations fits is sometimes as significant as the instrument's. This is particularly the case with CTD measurements where correlations between variables contribute mainly to decreasing the uncertainty of <I>S</I>, even when expanded uncertainties of conductivity cell calibrations are for the most part in the order of 0.002 mS cm<sup>−1</sup>. The relations given here, and obtained with the normalized GUM method, allow a real analysis of the uncertainties' sources and they can be used in a more general way, with instruments having different specifications. |
| first_indexed | 2024-04-13T15:14:14Z |
| format | Article |
| id | doaj.art-3a671dfe9031413a898e0ac59525ea96 |
| institution | Directory Open Access Journal |
| issn | 1812-0784 1812-0792 |
| language | English |
| last_indexed | 2024-04-13T15:14:14Z |
| publishDate | 2011-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Ocean Science |
| spelling | doaj.art-3a671dfe9031413a898e0ac59525ea962022-12-22T02:41:55ZengCopernicus PublicationsOcean Science1812-07841812-07922011-10-017565165910.5194/os-7-651-2011About uncertainties in practical salinity calculationsM. Le MennIn the current state of the art, salinity is a quantity computed from conductivity ratio measurements, with temperature and pressure known at the time of the measurement, and using the Practical Salinity Scale algorithm of 1978 (PSS-78). This calculation gives practical salinity values <I>S</I>. The uncertainty expected in PSS-78 values is ±0.002, but no details have ever been given on the method used to work out this uncertainty, and the error sources to include in this calculation. Following a guide published by the Bureau International des Poids et Mesures (BIPM), using two independent methods, this paper assesses the uncertainties of salinity values obtained from a laboratory salinometer and Conductivity-Temperature-Depth (CTD) measurements after laboratory calibration of a conductivity cell. The results show that the part due to the PSS-78 relations fits is sometimes as significant as the instrument's. This is particularly the case with CTD measurements where correlations between variables contribute mainly to decreasing the uncertainty of <I>S</I>, even when expanded uncertainties of conductivity cell calibrations are for the most part in the order of 0.002 mS cm<sup>−1</sup>. The relations given here, and obtained with the normalized GUM method, allow a real analysis of the uncertainties' sources and they can be used in a more general way, with instruments having different specifications.http://www.ocean-sci.net/7/651/2011/os-7-651-2011.pdf |
| spellingShingle | M. Le Menn About uncertainties in practical salinity calculations Ocean Science |
| title | About uncertainties in practical salinity calculations |
| title_full | About uncertainties in practical salinity calculations |
| title_fullStr | About uncertainties in practical salinity calculations |
| title_full_unstemmed | About uncertainties in practical salinity calculations |
| title_short | About uncertainties in practical salinity calculations |
| title_sort | about uncertainties in practical salinity calculations |
| url | http://www.ocean-sci.net/7/651/2011/os-7-651-2011.pdf |
| work_keys_str_mv | AT mlemenn aboutuncertaintiesinpracticalsalinitycalculations |