2013 Fiscal Year Final Research Report

Numerical modelling of the fall-rate behaviour of a free-fall ocean sensor and its validation

Research Project

Project/Area Number	23540506
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Multi-year Fund
Section	一般
Research Field	Meteorology/Physical oceanography/Hydrology
Research Institution	Tohoku University
Principal Investigator	HANAWA Kimio 東北大学, 理学(系)研究科(研究院), 教授 (40142921)
Project Period (FY)	2011 – 2013
Keywords	XBT / 降下速度 / 水温計測 / 水温 / 海洋貯熱量 / 海洋温暖化
Research Abstract	This study attempted to quantify and model the impact of variance in probe weight on the fall-rate of XBT (expendable bathythermograph), which has been a major tool for ocean temperature profiling over the last half a century. Based on a series of direct comparisons, the change of fall-rate of T-7, the most popularly-used probe type, caused by a change of 10g in its probe weight is estimated to be about 1%. This is almost equal to the relative weight change. When this is applied to the manufacturers' weight tolerance in their QC, the influence of weight change on the fall-rate is reasonably confined, and the results of this study give some upper limit on the XBT fall-rate bias, which has been a matter of debate over the last decade for the improvement of the historical ocean temperature data archive.