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Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.


A new method of calibrating Inverted Echo Sounder (IES) travel time measurements to main thermocline depths is described. Unlike the traditional method in which the thermocline is defined by a point measurement, such as the depth of the 12oC isotherm depth as measured with an XBT, this technique utilizes the full temperature profile of XBT casts. The advantage of this method is that the vertical integral of temperature, QT=∫Tdz is conceptually and empirically very closely correlated with the acoustic travel time measured by the IES, τ=2∫c-1dz. Comparisons of the new method with the more traditional point method show that the root-mean-square error in the calibration (11 m standard deviation) is 1/3 as large as before, and outlier values are significantly reduced. The final coefficients used to calibrate the SYNOP Central and Inlet Array IESs are tabulated.