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- Title
Diurnal Sea Breezes Force Near-Inertial Waves along Rottnest Continental Shelf, Southwestern Australia.
- Authors
Mihanović, Hrvoje; Pattiaratchi, Charitha; Verspecht, Florence
- Abstract
Observations of upper-ocean dynamics close to the critical latitude (ratio of the local inertial to diurnal frequency is 0.94) from a range of platforms (surface currents using HF radar, moored instruments, and satellite remote sensing data) off southwest Australia indicated the presence of energetic, near-inertial waves generated through the diurnal-inertial resonance. During the austral summer, when southerly winds and land-sea breeze (LSB) system dominated the wind regime, strong counterclockwise diurnal motions (amplitudes surpassing 0.3 m s−1) penetrated to 300-m depth with diurnal vertical isotherm fluctuations up to 60 m. The upward phase propagation speed of ~140 m day−1, deep penetration of diurnal currents below the mixed layer, and the ~180° phase difference between the upper and lower water column suggested that the local LSB system caused the resonant diurnal motions. Relative vorticity fluctuations along two cross-shore transects indicated changes to the local effective Coriolis frequency by more than 50% (±0.5 f). In the presence of strong and relatively consistent cross-shore diurnal wind forcing in the study area, the main factors that controlled the observed energetic but sporadic near-inertial oscillations were the Leeuwin Current strength and spatial-temporal variations. These variations controlled the effective Coriolis frequency and enabled the effective pumping of diurnal wind energy into the ocean particularly when the effective Coriolis frequency was ~24 h.
- Subjects
OCEAN dynamics; CONTINENTAL shelf; SEA breeze; INERTIA (Mechanics); OCEAN waves
- Publication
Journal of Physical Oceanography, 2016, Vol 46, Issue 11, p3487
- ISSN
0022-3670
- Publication type
Article
- DOI
10.1175/JPO-D-16-0022.1