Characteristics of Semi-diurnal and Diurnal Currents at a KOGA Station over the East China Sea Shelf
2
조회
0
다운로드
0
인용
0
참고문헌
키워드
초록
The long-term mooring performed at a KOGA station, located at about 30o20'N, 126o12'E in the East China Sea shelf, shows some different behaviors between “semi-diurnal” and “diurnal currents” defined as the currents with periods around, respectively, a half day and a day. They appear to be predominantly tidal having significant coherences with sea level changes around the semi-diurnal and diurnal frequencies. The “semi-diurnal current” is strongly barotropic all year round. However, contrastingly, it is largely baroclinic in summer in the area about 70 km nearer to the continental slope, referred to as the “slope-area”, as was found in previous current observations. The “diurnal current” of tidal origin is strongly barotropic in winter. In spring and summer, however, it becomes more baroclinic although it still remains largely barotropic, also showing more of its barotropic nature than in the “slope-area”. The inertial oscillation contributing to the “diurnal current” appears to be more prominent when the current is baroclinic, indicating the important role played by stratification in generation of inertial oscillations. Downward energy propagation of inertial oscillation is not observed, suggesting that it is not created at the surface by wind. Considering that the study area is both near a critical latitude and proximity to the continental slope, it is suggested that parametric subharmonic instability (PSI) plays a significant role in creating the baroclinic inertial oscillation.
Abstract
The long-term mooring performed at a KOGA station, located at about 30o20'N, 126o12'E in the East China Sea shelf, shows some different behaviors between “semi-diurnal” and “diurnal currents” defined as the currents with periods around, respectively, a half day and a day. They appear to be predominantly tidal having significant coherences with sea level changes around the semi-diurnal and diurnal frequencies. The “semi-diurnal current” is strongly barotropic all year round. However, contrastingly, it is largely baroclinic in summer in the area about 70 km nearer to the continental slope, referred to as the “slope-area”, as was found in previous current observations. The “diurnal current” of tidal origin is strongly barotropic in winter. In spring and summer, however, it becomes more baroclinic although it still remains largely barotropic, also showing more of its barotropic nature than in the “slope-area”. The inertial oscillation contributing to the “diurnal current” appears to be more prominent when the current is baroclinic, indicating the important role played by stratification in generation of inertial oscillations. Downward energy propagation of inertial oscillation is not observed, suggesting that it is not created at the surface by wind. Considering that the study area is both near a critical latitude and proximity to the continental slope, it is suggested that parametric subharmonic instability (PSI) plays a significant role in creating the baroclinic inertial oscillation.
참고문헌 (19)
- Baines PG, "On internal tide generation models", Deep-Sea Res, 29(3), pp.307~338 (1982)
- Choi BH, "A tidal model of the Yellow Sea and the Eastern China Sea", KORDI, pp.72~ (1980)
- Emery WJ, "Data analysis methods in physical oceanography", pp.638~ (1997), Elsevier
- Ichikawa H, "The Current System in the Yellow and East China Seas", J Oceanogr, 58(1), pp.77~92 (2002)
- Isobe A, "Recent advances in ocean-circulation research on the Yellow Sea and East China Sea shelves", J Oceanogr, 64(4), pp.569~584 (2008)
- Reports of the project, Analyses of data obtained from Korea Ocean Observing Network (KOON), "KHOA", 271~ (2012)
- "IEODO Ocean Research Station" (2013)[URL]
- Kuroda Y, "Observation of internal tides in the East China Sea with an underwater sliding vehicle", J Geophys Res-Oceans, 100(C6), pp.10801~10816 (1995)
- Larsen LH, "East China Sea tide currents", Cont Shelf Res, 4(1-2), pp.77~103 (1985)
- Lie HJ, "On the origin of the Tsushima Warm Current", J Geophys Res-Oceans, 99(C12), pp.25081~25091 (1994)
- Lie HJ, "Does the Yellow Sea Warm Current really exist as a persistent mean flow?", J Geophys Res-Oceans, 106(C10), pp.22199~22210 (2001)
- MacKinnon JA, "Parametric Subharmonic Instability of the Internal Tide at 29oN", J Phys Oceanogr, 43(1), pp.17~28 (2013)
- Niwa Y, "Three-dimensional numerical simulation of M2 internal tides in the East China Sea", J Geophys Res-Oceans, 109(C4), pp.C04027~ (2004)
- 박재훈, "Observation of Semi-diurnal Internal Tides and Near-inertial Waves at the Shelf Break of the East China Sea", Ocean and Polar Research, 33(4), pp.409~419 (2011), 한국해양과학기술원
- Pawlowicz R, "Classical tidal harmonic analysis including error estimates in MATLAB using T_TIDE", Comput Geosci, 28(8), pp.929~937 (2002)
- Su J, "Circulation dynamics of the China Seas north of 18oN", J Korean Soc Oceanogr, 11, pp.483~505 (1998)
- Takahashi D, "Mean field and annual variation of surface flow in the East China Sea as revealed by combining satellite altimeter and drifter data", Prog Oceanogr, 111, pp.125~139 (2013)
- Torrence C, "A Practical Guide to Wavelet Analysis", B Am Meteorol Soc, 79(1), pp.61~78 (1998)
- Yanagi T, "Co-tidal and corange charts for the East China Sea and the Yellow Sea derived from satellite altimetric data", J Oceanogr, 53(3), pp.303~310 (1997)