Abstract
This paper presents the conception and the metrological characterization of a new surface drifting buoy, designed to comply with the requirements of satellite sea-surface temperature measurement validation and to link, per comparison, these measurements to the SI. The reliability of this comparison is ensured by a High Resolution Sea-Surface Temperature (HRSST) sensor associated with a pressure sensor in a module called MoSens. This module can be calibrated in a laboratory to ensure traceability to the SI with an expanded uncertainty inferior to 0.01 °C. Once integrated in a number of buoys, the resulting network will contribute to create a fiducial reference measurement network. The pressure sensor can be used to estimate the sea-state, which is important to consider in order to understand the comparison with satellite data. Two buoy prototypes have been tested at sea during several weeks and compared in situ to reference thermometers, demonstrating their reliability and the accuracy of temperature measurements.
Highlights
Sea-Surface Temperatures (SST) play a key role in the understanding of the ocean-atmosphere interactions, in the characterization of the mesoscale variability of the upper ocean, and as inputs of numerical weather prediction systems
When two temperatures measured by previous High Resolution Sea-Surface Temperature (HRSST) buoys are compared, the differences can be reduced to within the digital sensor trueness by considering only wellmixed conditions, selected when the waves in the ERA-Interim (Dee et al, 2011) reanalysis are above 3 m in significant wave height
The goal of this study relates to the conception and the metrological characterization of new surface drifting buoys, design to comply with the requirements of SST satellites measurements validation and to link through comparison these measurements to the Système International d’unités (SI)
Summary
Sea-Surface Temperatures (SST) play a key role in the understanding of the ocean-atmosphere interactions, in the characterization of the mesoscale variability of the upper ocean, and as inputs of numerical weather prediction systems. If random components come from the variability in time and space of the thermal and dynamical states of the sea, in the case of SVP drifters, the biggest part of systematic components can come from the buoy and sensor conception and from the unknown temporal drift of their SST sensors This short review underlines the need to develop a new concept of surface drifting float which would be characterized in metrology laboratory. This need was described in a EUMETSAT tender, the goal of which was to build a Fiducial Reference Measurements (FRM) network of 100 high-resolution SST drifting buoys for the Copernicus Sentinel satellites validation The development of this network echoes for the ocean surface, the need raised by Immler et al (2010) for upper-air measurements, to constitute an independent infrastructure based on a different measurement principle and for which uncertainties are defined. Beyond the needs underlined by the review, this development answers the necessity of assuring long-term stability of references (World Meteorological Organization, 2016), the uncertainties of which are fully characterized by a metrological approach, for climate change studies
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