A%20Comparison%20of%20Six%20Expendable%20Bathythermograph%20Data%20Acquisition%20Systems - PowerPoint PPT Presentation

Title: A%20Comparison%20of%20Six%20Expendable%20Bathythermograph%20Data%20Acquisition%20Systems


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A Comparison of Six Expendable Bathythermograph
Data Acquisition Systems
Derrick Snowden Molly Baringer Gustavo Goni
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Instruments List
366 total profiles
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XBT Errors
A
B

• XBT differs from the CTD due to
• A inaccurate depth measurements
• B inaccurate temperature measurements

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Fall Rate Error Initial Conditions
Hallock and Teague 1992
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Fall Rate Equation
e.g. Hallock and Teague (1992)
a Change of mass of the probe due to spooling
wire. b Probe geometry and initial terminal
velocity c Describes startup transients i.e.
initial conditions
Currently used FRE (WMO 177052) for Deep Blue
probes contains no constant term ( c ).
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Determining Depth Offset
Hanawa et al (1995)
Focus on the temperature gradient derivative of
temperature with respect to depth Minimize
temperature error effect
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Depth Offset Prior to Correction
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Depth Correction Algorithm

• Assemble the depth offsets (dZ)
• Recalculate XBT depths
• Znew ZxbtdZ
• Back calculate time (t)
• Fit new fall rate equation to (t)
• z at2 bt c

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Depth Offset Post-Correction
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Summary of Fall Rate Coefficients
A B C
Wmocode 52 -0.00225 6.691 0
this study -0.00191 6.487 0
this study -0.00299 6.639 -4.5117
other studies (1) -0.00131 -0.00329 6.440 6.798 0 - 0
1 Taken from Hanawa et al 1995
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