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2002 LAPCOD Meeting
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A Catch-and-Release Drifter that Resolves Characteristic Scales of Coastal Dynamics
Carter Ohlmann, Andy Sybrandy, and Peter Niiler
University of California, Santa Barbara
carter@icess.ucsb.edu(Abstract received 10/02/2002 for session C)
ABSTRACT
An improved drifter for use in the coastal zone is presented. The near-shore drifter records position with GPS and transmits position data in near real-time using the Mobitex narrow band, data-only, cellular communications system. Driftr position is accurate to within 10 meters in the southern California region. Position updates can be recorded and transmitted every minute. The spatial and temporal resolution enables characteristic near-shore circulation patterns to be properly resolved. Spatial accuracy and near real-time data transmission make the drifters recoverable, so they can be used in catch-and-release manner. Rechargeable Ni-Cad batteries support communications for more than a week when sampling every 10 minutes. The drifters employ a Tri-Star type drogue at 1 m with slip believed to be 0.1-0.2% of the wind speed. Field tests suggest cellular coverage is adequate for reliable communications throughout almost the entire Santa Barbara channel (20 km offshore). Drifters are expected to properly update and communicate when located on the continental shelf off the shore of other coastal cities. Three preliminary deployments of up to 18 drifters occurred between 29 April and 2 May 2002 off the Santa Barbara coast. Conditions during the period ranged from calm to rough, with sustained winds over 12 m/s and 3 to 6 foot wind waves (NOAA/NWS buoy 46053). Drifters were released on the inner-shelf in water depths between 15 and 80 m. Drifters typically transmitted their position every 10 minutes for a single day, but were left to sample continuously for up to 5 days. Occasional data losses and erroneous GPS position updates occurred due to a problem with configuration of the drifter GPS modules (believed to be remedied). All drifters were recovered and are available for future use. Repeated deployments of the coastal drifters will greatly enhance the understanding of near-shore circulation.
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2002 LAPCOD Meeting, Key Largo, Florida, December 12-16, 2000