The IEEE Seventh Working Conference on Current Measurement Technology

Current and Wave Monitoring and Emerging Technologies

March 13-15 | Bahia Hotel | San Diego, CA, USA

  
     

The Effects of Mobile Scatterers on the Quality of ADCP Data in Differing Marine Environments

Andrew N Moore

Status: Accepted

Fugro GEOS Ltd
Gemini House, Hargreaves Road
Swindon , Wilts UK
SN25 5AL

Phone: +44 1793 746409
Email: a.moore@geos.com

Co-Authors:
Dr Douglas L Stewart
Fugro GEOS Ltd
Swindon

Acoustic Doppler Current Profilers (ADCP) are now regularly used to measure current profiles in waters from the shallowest coastal region to the most extreme deepwater site. Numerous different frequencies of instrument are employed to cover vertical bin depths of a few centimetres to many tens of metres. The common factor between them all is that they rely on particles (scatterers) within the water column to reflect back the acoustic signal transmitted by the instrument. In order for the technique to function, these scatterers must be assumed to move with the ocean flow.

Current velocity data have been collected in a number of geographical areas where these scatterers appear to move independent of the current flow. Several different effects have been identified, the commonest one being the diurnal vertical migration of plankton and grazers, which can be identified by high vertical velocities at dawn and dusk. At times the system is further complicated by filter-feeders that appear to swim with a significant horizontal component to their velocity against or at least non-coincident with the main current flow. This can be seen as peaks in the horizontal current speed trace from the ADCP at the same times each day.

While the diurnal transports of plankton and nekton are well known, the paper focuses on the current velocity data. Examples are shown of the main types of effect on data sets recorded in some of the major deepwater exploration regions of the world and looks at methods of removing the erroneous data from the real current velocity.

Submitted on November 12, 2002