Abstract
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.
Highlights
Accurate data of uniform quality is critical to obtaining robust results in the Earth Sciences
Many scientists recognize that sensor calibration prior to deployment is an absolute requirement in order to detect such small signals
We introduce a new method of pre-deployment sensor calibration and demonstrate its importance in Argo float sensor calibration as part of the framework of the Argo program in the global ocean observation system
Summary
Accurate data of uniform quality is critical to obtaining robust results in the Earth Sciences This data can be very difficult to obtain in situations with a smaller signal-to-noise ratio when using spatially and temporally broad observation systems. Hosoda et al Progress in Earth and Planetary Science (2019) 6:65 within the range of 0.01~ 0.001 °C or PSS-78 (e.g., Jacobs and Giulivi 2010; Purkey and Johnson 2010). This seems quite small, this variability associated with climate change signals is meaningful. We introduce a new method of pre-deployment sensor calibration and demonstrate its importance in Argo float sensor calibration as part of the framework of the Argo program in the global ocean observation system
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