Accuracy of Florida Current Volume Transport Measurements at 27°N Using Multiple Observational Techniques

Abstract For more than 30 years, the volume transport of the Florida Current at 27°N has been regularly estimated both via voltage measurements on a submarine cable and using ship-based measurements of horizontal velocity at nine historical stations across the Florida Straits. A comparison of three...

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Bibliographic Details
Published in:Journal of atmospheric and oceanic technology 2014-05, Vol.31 (5), p.1169-1180
Main Authors: Garcia, Rigoberto F, Meinen, Christopher S
Format: Article
Language:English
Subjects:
Accuracy
Acoustic Doppler Current Profiler
Doppler radar
Doppler sonar
Dropsonde
Dropsondes
Electrical measurement
Estimates
Evaluation
First principles
Global positioning systems
GPS
Measurement techniques
Navigation systems
Ocean currents
Ships
Submarine cables
Submarines
Undersea cables
Velocity
Volume
Volume transport
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Summary:Abstract For more than 30 years, the volume transport of the Florida Current at 27°N has been regularly estimated both via voltage measurements on a submarine cable and using ship-based measurements of horizontal velocity at nine historical stations across the Florida Straits. A comparison of three different observational systems is presented, including a detailed evaluation of observational accuracy and precision. The three systems examined are dropsonde (free-falling float), lowered acoustic Doppler current profiler (LADCP), and submarine cable. The accuracy of the Florida Current transport calculation from dropsonde sections, which can be determined from first principles with existing data, is shown to be 0.8 Sv (1 Sv ≡ 10 6 m 3 s −1 ). Side-by-side comparisons between dropsonde and LADCP measurements are used to show that the LADCP-based transport estimates are accurate to within 1.3 Sv. Dropsonde data are often used to set the absolute mean cable transport estimate, so some care is required in establishing the absolute accuracy of the cable measurements. Used together, the dropsonde and LADCP sections can be used to evaluate the absolute accuracy and precision of the cable measurements. These comparisons suggest the daily cable observations are accurate to within 1.7 Sv, and analysis of the decorrelation time scales for the errors suggests that annual transport averages from the cable are accurate to within 0.3 Sv. The implications of these accuracy estimates for long-term observation of the Florida Current are discussed in the context of maintaining this key climate record.
ISSN:0739-0572
1520-0426
DOI:10.1175/JTECH-D-13-00148.1