Nortek Aquadopp Current Meter Data from an Equatorial Pacific Surface Mooring

Lee Gordon

NortekUSA
9948 Hibert St., #102
San Diego, CA 92131
Phone: 858-586-0900
Fax: 858-586-0110
lgordon@NortekUSA.com
www.NortekUSA.com

This report summarizes results from a Nortek Aquadopp Current Meter mounted on a taut-line surface mooring at 170?W on the Equator (about 3500 km northeast of Australia). This report compares data collected by the Aquadopp with a second acoustic current meter, and it illustrates what we can learn from an Aquadopp about the motion of the mooring itself.

The mooring was deployed by PMEL on July 3, 2000 and recovered on October 31, 2000. The Aquadopp was mounted 55 m deep, just below the ACM, which was mounted 52 m deep. Both instruments recorded data every 10 minutes. Each Aquadopp measurement was an average of 1 minute of data. The Aquadopp was set to use its 6 dB power level (four power levels are available: 0, 6 dB, 12 dB and 18 dB, all relative to the lowest power level). Both instruments performed normally, and they produced comparable mean currents.

Aquadopps include a special diagnostic mode, which provides periodic short bursts of 1-s data. The diagnostic mode's rapid sampling provides the means to understand mooring motions, which occur largely near wave frequencies. A taut-line equatorial mooring is a particularly appropriate place to develop this understanding because the surface buoy transmits wave motions deep into the water through the mooring line.