Journal of Oceanography

, Volume 61, Issue 1, pp 115–121

A New Fall-Rate Equation for T-5 Expendable Bathythermograph (XBT) by TSK


DOI: 10.1007/s10872-005-0024-4

Cite this article as:
Kizu, S., Yoritaka, H. & Hanawa, K. J Oceanogr (2005) 61: 115. doi:10.1007/s10872-005-0024-4


The accuracy of the manufacturer’s fall-rate equation for the T-5 Model of expendable bathythermograph (XBT) has been investigated based on about 300 collocated pairs of XBT-CTD (Conductivity-Temperature-Depth profiler) measurements in various climatological regions. We found that the equation systematically overestimates depth by about 5% for the T-5 produced by Tsurumi Seiki, Co. Ltd. (TSK), but almost no bias is associated with the T-5 produced by Sippican, Inc., in USA. The cause of this difference is not clear, because the two manufacturers’ T-5 probes are reported to have identical shape and weight in water. We propose a new fall-rate equation for the TSK T-5: z(t) = 6.54071t - 0.0018691t2, where z(t) is depth in meters at time, t, in seconds.


T-5 XBT expendable bathythermograph fall-rate equation temperature measurement VOS monitoring 

Copyright information

© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  1. 1.Department of Geophysics, Graduate School of ScienceTohoku UniversityAoba-ku, SendaiJapan
  2. 2.Japan Coast Guard AcademyJapan

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