An Intercomparison of Four Models of Current Meter in High Current Conditions in Drake Passage

• Main Authors: Kennelly, Maureen A., Watts, D. Randolph, Tracey, Karen L., Donohue, Kathleen A.
• Format: Text
• Language: unknown
• Published: DigitalCommons@URI 2012
• Subjects: current meter comparisions; acoustic Doppler current sensors; Drake Passage
• Online Access: https://digitalcommons.uri.edu/physical_oceanography_techrpts/3; https://digitalcommons.uri.edu/context/physical_oceanography_techrpts/article/1002/viewcontent/CM_cookoff_TR.pdf

Seven current meters representing four models were placed for an 11 month deployment on a stiffly buoyed mooring to intercompare their velocity measurements: two VMCMs, two Aanderaa RCM11s, two Aanderaa SEAGUARDSs, and a Nortek Aquadopp. The current meters were placed 6 m apart from each other at about 4000 m depth in an area of Drake Passage expected to have strong near-bottom currents, that were nearly independent of depth. Two high-current events occurred in bursts of semi-diurnal pulses lasting several days, one with peak speeds up to 67 cm/s and the other above 35 cm/s. The current speed measurements all agreed within about 5% when vector-averaged over simultaneous time intervals: the full time interval (198 days) when all instruments were working, and the two high-speed events lasting 21 days and 7 days. The VMCMs, chosen as the reference measurements, were found to measure the median of the mean-current magnitudes. The RCM11 and SEAGUARD current speeds had a nearly 1:1 relationship with the median. They agreed within 2% at higher speeds (35-70 cm/s), whereas in lower speed ranges (0-35 cm/s) the vector-averaged speeds for the RCM11s and SEAGUARDS were, respectively, 4-5% lower and 3-5% higher than the median. The Aquadopp current speeds were about 7% higher than the VMCMs over the range (0-40 cm/s) encountered through their shorter common time period.