Publication policy of XBT fall-rate bias correction data

Analyses of concurrent XBT, CTD and Argo float observations indicate that there is a systematic difference in temperature profiles. Gouretski and Koltermann (2007) shows statistics from Expendable Bathythermograph (XBT) vs. Conductivity-Temperature-Depth (CTD)/reversing thermometer instrument comparisons which reveal a warm bias in XBT temperatures. The bias may be due to errors in the calculation of depth or in measurement of the temperature. A NOAA sponsored XBT Fall Rate Workshop was held to discuss this problem. Estimates of corrections recently published or submitted to scientific journals are provided here.

Those XBT data with observed level data for World Ocean Database 2009 do not have any adjustments, This may be due to the recommendation of UNESCO(1994) that XBT data for archive and exchange should use non adjustment data to avoid confusing. However, data for T-5s have either no adjustment (Sippican) or a small adjustment (for TSK models) (Kizu et al., 2005). Information on the decision made on depth adjustment is included for each XBT data.

UNESCO (1994), Calculation of New Depth Equations for Expendable Bathythermographs Using a Temperature-Error-Free Methods (Application to Sippican/TSK T-7, T-6 and T-4 XBTs), IOC Technical Series No. 42, 46 pp. (by Hanawa, K., P. Rual, R. Bailey, A. Sy, and M. Szabados)

So, non adjustment XBT data are normally published from the "JAMSTEC Data Site for Research Cruises", but JAMSTEC also provide web page to publish fall-rate bias correction data for TSK T-5 XBTs. It should be noted that the fall-rate equation coefficients used here are not offered by manufacturer. Therefore, these data may be replaced if new fall-rate equation coefficients for TSK T-5 XBT are offered by manufacturer or any other more suitable fall-rate equation is published.