Search Results

You are looking at 1 - 2 of 2 items for

  • Author or Editor: Satoshi Ozawa x
  • Refine by Access: All Content x
Clear All Modify Search
Hiroshi Uchida, Kentaro Ohyama, Satoshi Ozawa, and Masao Fukasawa

Abstract

A Sea-Bird Electronics (SBE 35) deep ocean reference thermometer is used with the SBE 9plus CTD system to calibrate the SBE 3 ocean thermometers of the CTD. The SBE 35 is standardized in water-triple-point and gallium-melting-point cells. The SBE 3 is calibrated with the SBE 35 under the assumption that discrepancies between SBE 3 and SBE 35 data are due to pressure sensitivity, the viscous heating effect, and time drift of the SBE 3. Based on the results of an in situ calibration, the pressure sensitivity and the viscous heating effect were evaluated for 11 SBE 3 thermometers. Three SBE 3s showed little pressure sensitivity, and eight had pressure sensitivities of 1–2 mK at 6000 dbar. The average viscous heating effect on the standard SBE 3 measurements was 0.5 mK. Both the accuracy and precision of the in situ calibrated SBE 3 data at depths greater than 2000 dbar were 0.4 mK relative to the SBE 35 reference.

Full access
Hiroshi Uchida, Toshiya Nakano, Jun Tamba, Januarius V. Widiatmo, Kazuaki Yamazawa, Satoshi Ozawa, and Takeshi Kawano

Abstract

The uncertainty of deep ocean temperature (~1°C) measurement was evaluated. The time drifts of six deep ocean standards thermometers were examined based on laboratory calibrations as performed by the manufacturer in triple point of water (TPW) cells and gallium-melting-point (GaMP) cells. The time drifts ranged from −0.11 to 0.14 mK yr−1. Three of the six thermometers were evaluated at the National Metrology Institute of Japan in five TPW cells and a GaMP cell, and the temperature readings agreed with the realized temperature of the national standard cells of Japan within ±0.14 and ±0.41 mK for TPW and GaMP, respectively. The pressure sensitivities of the deep ocean standards thermometers were estimated by comparison with conductivity–temperature–depth (CTD) thermometers in the deep ocean, and no notable difference was detected. Pressure sensitivities of the two CTD thermometers were examined by laboratory tests, and the results suggest that the deep ocean standards thermometers have no pressure sensitivity, at least up to 65 MPa. The position and attitude motion of the CTD system can affect temperature and salinity data quality. The overall expanded uncertainty of the deep ocean temperature measurement (up to 65 MPa) by the CTD thermometer calibrated in reference to the deep ocean standards thermometer is estimated to be 0.7 mK.

Full access