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Water-following characteristics of a mixed layer drifter

Water-following characteristics of a mixed layer drifter

Authors :
Henry J. White
Pearn P. Niller
Russ E. Davis
Source :
Deep Sea Research Part A. Oceanographic Research Papers. 34:1867-1881
Publication Year :
1987
Publisher :
Elsevier BV, 1987.

Abstract

Accurate measurements of mean Lagrangian displacements of water parcels in the mixed layer are difficult to make because wave forces on objects that float on or near the ocean surface can be easily rectified to produce a unidirectional motion. Here we discuss a design for an ARGOS-tracked drifter that is configured so as to minimize surface wave effects, and present measurements of its water-following characteristics in the California Current system in July 1985 at 15 m nominal depth in a small range of wind and wave conditions. The unique features of the drifter are small, spherically symmetric, surface and subsurface floats (to reduce directional wave forces) and a large, semi-rigid, three-axis symmetric drogue in the shape of a corner-radar reflector (to reduce kiting in shear) that self-deploys from a folded configuration. Relative 1–2 h mean flows of 0.6–2.9 cm s −1 past the drogue were measured with two vector-measuring current meters (VMCM's) attached to the top and bottom of the drogue in the presence of significant wave heights of 0.3–2.2 m, wind speeds of 2–10 m s −1 , and mean vertical shears of 0.34–3.12 × 10 −2 s −1 . A drag force model shows that the most significant forces in the least square sense are due to winds or surface gravity waves, jointly accounting for 74% of the variance. In July 1985, 20 drogues were released in the vicinity of 31°N, 120°W. Although the encapsuled ARGOS transmitter in the small surface sphere submerged a significant portion of time, an average of 5 out 6 possible ARGOS positions were obtained daily. Recovery and inspection of one drifter both 4 and 8 months after deployment in the California Current revealed the conditions of the mechanical components to be excellent.

Details

ISSN :
01980149
Volume :
34
Database :
OpenAIRE
Journal :
Deep Sea Research Part A. Oceanographic Research Papers
Accession number :
edsair.doi...........8e19355256dedb2519857365798c4ca1
Full Text :
https://doi.org/10.1016/0198-0149(87)90060-4