Open AccessSeasonal variations in the speed factor and deflection angle of the wind‐driven surface flow in the Tsushima Strait
Author(s) -
Yoshikawa Y.,
Masuda A.
Publication year - 2009
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jc005632
Subject(s) - wind speed , geostrophic wind , geology , deflection (physics) , radar , deflection angle , flow velocity , shear velocity , atmospheric sciences , meteorology , geodesy , environmental science , flow (mathematics) , mechanics , climatology , physics , turbulence , oceanography , optics , telecommunications , computer science
The speed factor and deflection angle of the wind‐driven surface flow were estimated for the Tsushima Strait from long (≥3.5 years) records of surface velocities measured with HF radar, geostrophic velocities estimated from sea level differences, and analyzed wind velocities. Large seasonal variations in both the speed factor and deflection angle were found. The speed factor, which is defined here as the ratio of the wind‐driven surface flow to the (waterside) friction velocity, is 7.7–9.5 in winter and 11.4–14.3 in summer, while the deflection angle is 17.7°–27.3° in winter and increases to 48.5°–67.3° in summer. A likely cause of these seasonal variations is the seasonal variation of the eddy viscosity profile. It was also found that the speed factor in winter increases with the friction velocity. This dependence is possibly explained by deepening of the wind‐driven surface flow with increasing friction velocity: as the friction velocity increases, HF radar (whose measurement depth is fixed) tends to measure a shallower part of the wind‐driven surface flow whose speed factor is larger.