XCP (Expendable Current Profiler) Performance Near the Geomagnetic Equator,
Abstract
Velocity profiles collected with an expendable current profiler (XCP) and with a recoverable free fall profiler, TOPS(Total Ocean Profiling System), are compared in the vicinity of the geographic and geomagnetic equators. The XCP operates on the principles of motional induction, measuring the electric currents that result from the movement of seawater through the vertical component of the earth's magnetic field. Induced electric currents that results from the movement of seawater through the vertical component of the earth's magnetic field. Induced electric currents are interpreted in terms of the oceanic velocity structure. TOPS is a freely falling profiler that utilizers acoustic tracking techniques to measure velocity structure at the longer vertical wavelengths (lambda > 20 m) and an onboard two axis acoustic velocimeter to measure fine structure (20 m > lambda > 20 cm). Previous mid-latitude intercomparisons showed these two profilers to agree within 1-2 cm/s rms. The present study, conducted in March-April 1982, took place in the eastern equatorial Pacific to compare profiler performance near the magnetic equator (8 deg 10 min S at 95 deg W). Results of measurements made along a transect from 3 deg N to 8 deg S are presented. As the magnetic equator is approached, the performance of the XCP relative to that of TOPS degrades because the vertical component of the geomagnetic field diminishes. The two major sources of error seem to be inadequate compensation for the fall rate and vessel interference. Probe to probe variability is attributed to electronic phase differences, which are more noticeable near the magnetic equator.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1986
- Accession Number
- ADA174105
Entities
People
- M. A. Kennelly
- P. A. Mckeown
- Thomas B. Sanford
Organizations
- University of Washington