FAQ – Sea Surface Salinity data base web access

1. What are the conditions of use of the data? arrow_circle_up

Data on this web interface have been collected and validated by the French Sea Surface Salinity Observation Service (SO-SSS).

The data are provided without any warranty for any non-profit educational and research purposes.

Publications using these data should acknowledge the SO-SSS and cite the following reference:
Alory G. et al., 2015. The French contribution to the Voluntary Observing Ships network of Sea Surface Salinity. Deep Sea Res., 105, 1-18, doi:10.1016/j.DSR.2015.08.005.

Copies should be sent to the contact email (sss-contact@legos.obs-mip.fr) so that to help us pursue and improve this Service.

The suggested sentence is: “Sea surface salinity data derived from voluntary observing ships were collected, validated, archived, and made freely available by the French Sea Surface Salinity Observation Service (http://www.legos.obs-mip.fr/observations/sss/)”.

2. What are the data format and metadata? arrow_circle_up

This web interface is designed to download the delayed mode quality controlled ThermoSalinoGraph (TSG) data as Netcdf or ascii files based on the GOSUD format.

Information on ship lines (route, time in operation…) can be found in the SO-SSS web site in the Monitoring System menu.

Metadata are included in the Netcdf and ascii files.

Main variables are:
SSS, SSS_QC, SSS_ERROR
SST, SST_QC, SST_ERROR

SSS is the Sea Surface Practical Salinity measured by the TSG (SSPS).
SST is the Sea Surface Temperature measured at intake (SSTP when available) or the Temperature measured by the TSG (SSJT).

When available, SSS and SST data are adjusted with external data (water samples, colocated Argo and/or Mooring data), to account for possible measurement drift of the TSG sensors mostly due to biofouling.

*_QC is the Quality Code we attributed to the data, based on potential instrumental problems and comparison with climatology.
Value of *_QC is:
0 for Uncontrolled data
1 for Good data
2 for Probably Good data
3 for Probably Bad data
4 for Bad Data
6 for Harbour data

*_ERROR is the estimated error of the TSG data computed by adjustment to external data. A SSS_ERROR equal to 1 or SST_ERROR equal to 0.5 means the error value is only a rough estimate due to a number of external data not statistically significant.

WARNING !

TSG data are not exactly surface measurements. The TSG water intake is generally located at a 5-10 m depth depending on the ship and its load.
SSTP is most of the time not available.
SSJT is biased warm compared to Ocean temperature, due to warming in the piping between the hull intake and the TSG, often located in the engine room. The warm bias is not constant and ranges within 0.2 to 1 °C.
When intending to use a given variable (e.g. SSS) for research purpose, we recommend to use, by order of preference and depending on availability:
1) SSS with SSS_QC=1 (Good data)
2) SSS with SSS_QC=2 (Probably Good data)

Note that the availability of these different quality data can change with time during a single ship journey.

3. How are the SSS data validated and corrected? arrow_circle_up

We use a dedicated software for interactive quality control of SSS, freely available at https://forge.ird.fr/us191/TSG-QC

4. Are there some references about data collection and/or quality control? arrow_circle_up

a) Grelet J., B. Buisson and C. Hénin, 1992. Installation et utilisation d’un thermo-salinographe à bord d’un navire marchand. Notes Techniques, Sciences de la mer, Océanographie physique, Vol. 7, Centre ORSTOM de Nouméa, Nouvelle Calédonie, 99 pp.

b) Hénin C. and J. Grelet, 1992. Automatisation de la mesure de la température et de la salinité de surface aux stations cotières et sur les navires du réseau d’observation dans I’océan Pacifique Tropical. Rapports Scientifiques et Techniques, Série Conventions, Sciences de la Mer, Océanographie Physique, V01.3, 28 pp.

c) Hénin C., and J. Grelet, 1996. A merchant ship thermosalinograph network in the Pacific Ocean. Deep-Sea Research I 43, 1833–1856.

d) Prunier-Mignot M., Varillon D., Foucher L., Ihily J.-M., Buisson B., Masia F., Henin C., Ioualalen M., Delcroix T., 1999. Users Guide for Thermosalinograph Installation and Maintenance Aboard a Ship. Notes Techniques, Sciences de la Mer, Oceanogr. Phys., Centre ORSTOM de Noumea, New Caledonia, vol. 13, 102pp.

e) Delcroix T., G. Alory, D. Diverrès, Y. Gouriou, S. Jacquin, C. Maes, R. Morrow, G. Reverdin, P. Téchiné, D. Varillon, 2010. Monitoring SSS in the global ocean from ships of opportunity : the French SSS observation service. In Proceedings of the OceanObs09 conference: “Sustained Ocean Observations and Information for Society”, Venice, Italy, 21-25 September 2009, Hall, J., Harrison D.E. and Stammer, D., Eds., ESA Publication WPP-306, 2010.

f) Alory G., T. Delcroix, P. Téchiné, D. Diverrès, D. Varillon, S. Cravatte, Y. Gouriou, J. Grelet, S. Jacquin, E. Kestenare, C. Maes, R. Morrow, J. Perrier, G. Reverdin and F. Roubaud, 2015. The French contribution to the Voluntary Observing Ships network of Sea Surface Salinity. Deep Sea Res., 105, 1-18, doi:10.1016/j.DSR.2015.08.005.

g) Alory G., P. Téchiné, T. Delcroix, D. Diverrès, D. Varillon, J.-R. Donguy, G. Reverdin, R. Morrow, J. Grelet, Y. Gouriou, S. Jacquin, E. Kestenare, C. Bachelier, A. DiMattéo. Le Service National d’Observation de la salinité de surface de la mer : 50 ans de mesures océaniques globales. La Météorologie, 109, 29-39, 2020, doi: 10.37053/lameteorologie-2020-0044

5. Where can I find information about ship routes? arrow_circle_up

Further information are available in the presently and formerly selected ships web pages.

6. What are the available data periods for the ships? arrow_circle_up

Available delayed-time processed SSS data.

7. Who do I contact for any enquiry or suggestion? arrow_circle_up

All enquiries and suggestions for improvements, regarding these data should be addressed to:

Gael ALORY – LEGOS/OMP – 14 Avenue Edouard Belin – 31400 TOULOUSE – FRANCE

Contact SSS

https://www.legos.omp.eu

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