The impact of improved thermistor calibration on the expendable bathythermograph profile data

Marlos Goes, Elizabeth A Babcock, Francis Bringas, Peter Ortner, Gustavo Goni

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Expendable bathythermograph (XBT) data provide one of the longest available records of upper-ocean temperature. However, temperature and depth biases in XBT data adversely affect estimates of long-term trends of ocean heat content and, to a lesser extent, estimates of volume and heat transport in the ocean. Several corrections have been proposed to overcome historical biases in XBT data, which rely on constantly monitoring these biases. This paper provides an analysis of data collected during three recent hydrographic cruises that utilized different types of probes, and examines methods to reduce temperature and depth biases by improving the thermistor calibration and reducing the mass variability of the XBT probes. The results obtained show that the use of individual thermistor calibration in XBT probes is the most effective calibration to decrease the thermal bias, improving the mean thermal bias to less than 0.02°C and its tolerance from 0.1° to 0.03°C. The temperature variance of probes with screened thermistors is significantly reduced by approximately 60% in comparison to standard probes. On the other hand, probes with a tighter weight tolerance did not show statistically significant reductions in the spread of depth biases, possibly because of the small sample size or the sensitivity of the depth accuracy to other causes affecting the analysis.

Original languageEnglish (US)
Pages (from-to)1947-1961
Number of pages15
JournalJournal of Atmospheric and Oceanic Technology
Volume34
Issue number9
DOIs
StatePublished - Sep 1 2017

Keywords

  • Bias
  • Error analysis
  • In situ oceanic observations
  • Ocean
  • Regression analysis
  • Ship observations

ASJC Scopus subject areas

  • Ocean Engineering
  • Atmospheric Science

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