The Joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology

Pilot Project for the Intercomparison of Seawater Salinity Measurements

Seawater salinity has become an important variable to measure in order to address the needs of operational application such as operational ocean forecasting, seasonal to inter-annual forecasting, climate monitoring and services, as well as those of physical oceanography research. Indeed, together with water temperature, ocean salinity drives water density, and as such is important for ocean circulation. Ocean surface salinity is also useful for monitoring and understanding the water cycle, which is linked for example to evaporation and precipitation over the oceans, river runoff, and the melting and freezing of sea ice. The requirements for salinity measurements are further documented in the WMO Database of observational user requirements (OSCAR), and in the Statements of Guidance for WMO Applications.

To assure that the products and services of the above applications, and the best possible use of the observations for operational and research applications, the accuracy of salinity measurements made at sea is essential. At present, salinity (or conductivity) is measured in situ using various types of instruments, including for example CTD from ships, Argo profiling floats, moored data buoys, and XCTDs. The instruments used with these types of platforms must be properly calibrated in the laboratory, and their traceability to SI units assured. For quality control purposes, natural seawater sampled at sea can be used for salinity analysis in the laboratory and for comparison with the corresponding in situ data. Substantial proficiency differences exist amongst the calibration laboratories in the world. Comparison of the laboratory proficiencies is one of a few effective methods for assuring reliable metrological comparability amongst the different salinity measuring systems.

JCOMM is therefore increasingly involved in intercomparison activities, and is organizing a pilot project for the intercomparison of seawater salinity measurements. The pilot project is organized with assistance and support from the Regional Marine Instrumentation Centre (RMIC) for the Asia Pacific Region (RMIC/AP) in Tianjin, China. The purpose of this project is to ascertain the overall proficiency of the agencies or institutes participating in the project for measuring seawater salinity. The project is particularly targeting laboratories involved in JCOMM global marine/ocean observation programmes. It is also expected that experiences obtained from this activity will be useful for establishing common JCOMM marine/ocean observation standards in the future.

Details about the pilot project, including organizing committee, workplan, implementation scheme, and operations guidelines can be found below:

If you are interested to participate, please download the required registration form from the website above, have them filled in as appropriate by the participating laboratory(ies) in your country (one form per laboratory), and return them by email to the WMO Secretariat no later than 25 May 2014 through the Permanent Representative of your Country with the WMO, or to the IOC Secretariat through the IOC Action Addressee of your country. The organizing committee will then select the participating laboratories, and steer the pilot activity according to the agreed upon operations guidelines. The goal is to have the pilot project completed by mid-September 2014, and publish the results through JCOMM Technical Reports series by the end of 2014.


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