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    • Progress in Earth and Planetary Science
    • Progress in Earth and Planetary Science
    • Progress in Earth and Planetary Science
    • Progress in Earth and Planetary Science
    Progress in Earth and Planetary Science

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    New method of temperature and conductivity sensor calibration with improved efficiency for screening SBE41 CTD on Argo floats

    Hosoda S, Hirano M, Hashimukai T, Asai S, Kawakami N

    CTD sensor, Sensor screening, SBE41, Simple calibration method, Water temperature control, Global Argo observation system

    New sensor calibration system for Argo float (J-Calibration).

    The global ocean monitoring system would benefit from improvements in the efficiency of Conductivity, Temperature, and Depth Device (CTD) sensor screening. Here, we describe the development of a new screening system, J-Calibration, for use with the SBE41 CTD sensor on the Argo float (Sea Bird Scientific). This new system has crucial advantages over the traditional SBE-Calibration system. First, J-Calibration does not require removal of the CTD sensor unit from the Argo float body to operate in a laboratory. This feature enables technicians or operators to more efficiently check the Argo target accuracies (± 0.005 °C for temperature and ± 0.01 PSS-78 for salinity) and allows the manufacturer’s warranty to remain intact. This also allows for a more efficient basic screening system which maintains screening accuracy without the need for specialized technicians. J-Calibration reduces the screening time to 1/6th that of SBE-Calibration and does not require the preparation of large amounts of artificial seawater. J-Calibration uses 1/23rd of the volume of seawater compared to SBE-Calibration by examining calibration at only 1 temperature point (22 °C), whereas SBE-Calibration requires 7 points to achieve calibration. The J-Calibration system does require careful temperature control of the artificial seawater as it is critical to maintain a uniform water temperature throughout the experiments. To satisfy this, using a vinyl greenhouse and covering sensors with adiabatic materials and cooling packs are effective. In comparison with the accuracy and system stability of SBE-Calibration, we show that the J-Calibration system is non-inferior and therefore is suitable for use in laboratory screening prior to deployment. Based on these advantages, the J-Calibration system will make a strong contribution to the deployment of healthy Argo fleets and to the maintenance of uniform data in the global ocean.