Journal of Geophysical Research: Oceans

Observations of near-inertial surface currents off Oregon: Decorrelation time and length scales

Authors

  • Sung Yong Kim,

    Corresponding author
    1. Division of Ocean Systems Engineering, School of Mechanical, Aerospace & Systems Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea
    • Corresponding author: Sung Yong Kim, Division of Ocean Systems Engineering, School of Mechanical, Aerospace & Systems Engineering, Korea Advanced Institute of Science and Technology, 291 Daehak-ro, Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea. (syongkim@kaist.ac.kr)

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  • P. Michael Kosro

    1. College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA
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Abstract

[1] High-resolution (km in space and hourly in time) surface currents observed by an array of high-frequency radars off Oregon are analyzed to quantify the decorrelation time and length scales of their near-inertial motions. The near-inertial surface currents are dominantly clockwise with amplitudes of 9–12 cm s−1. However, they appear asymmetric and elliptical as a result of counterclockwise inertial motions with magnitudes in a range of 2–5 cm s−1. The decorrelation time and length scales are computed from the decay slope of the near-inertial peak and the spatial coherence in the near-inertial frequency band, respectively. Decorrelation time scales of clockwise near-inertial motions increase from 2 days nearshore (within 30 km from the coast) to 6 days offshore, and their length scales increase from 30 to 90 km seaward possibly due to coastal inhibition. The local spatial coherence has an exponentially decaying structure for both clockwise and counterclockwise rotations, and their phases propagate northwestward (offshore) for clockwise and northeastward (onshore) for counterclockwise rotations.

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