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Turbulent bottom Ekman boundary layer measured over a continental shelf
Author(s) -
Yoshikawa Y.,
Endoh T.,
Matsuno T.,
Wagawa T.,
Tsutsumi E.,
Yoshimura H.,
Morii Y.
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl044156
Subject(s) - acoustic doppler current profiler , ekman layer , ekman transport , eddy diffusion , geology , turbulence , buoyancy , continental shelf , boundary layer , turbulence kinetic energy , turbulence modeling , oceanography , meteorology , current (fluid) , physics , upwelling , mechanics
An acoustic Doppler current profiler was deployed in summer and autumn in 2007–2009 at two stations on the East China Sea shelf. Clear velocity spirals that basically correspond to theoretical Ekman spirals were identified for both mean and tidal currents. From these spirals and the corresponding Ekman equation, we estimated the time‐averaged eddy viscosity ( μ ) profiles. The estimated μ was largest (2–3 × 10 −3 m 2 s −1 ) around 5 m from the bottom and decreased almost exponentially with height. A qualitatively similar profile of the eddy diffusivity was also inferred from the acoustic Doppler current profiler data and microstructure profiler data. The flux Richardson number was estimated as 0.11 ± 0.10 ∼ 0.46 ± 0.17, indicating relatively large buoyancy contribution to the turbulent kinetic energy budget.