Submesoscale Eddies in the Taiwan Strait Observed by High-Frequency Radars: Detection Algorithms and Eddy Properties

AbstractThis study compared the efficiencies of two widely used automatic eddy detection algorithms—that is, the winding-angle (WA) method and the vector geometry (VG) method—and investigated the submesoscale eddy properties using surface current observations derived from high-frequency radars (HFRs) in the Taiwan Strait. The results showed that the WA method using the streamline and the VG method based on the streamfunction field have almost the same capacity for identifying eddies, but the former is more competent than the latter in capturing the eddy size. The two algorithms simultaneously identified 1080 submesoscale eddies, with the centers and boundaries determined only by the WA method, and they were further used to investigate the eddy properties. In general, no significant difference was observed between the cyclonic and anticyclonic eddies in terms of radius, life span, and kinematics, as well as the evolution during their life cycles. The typical radius of the eddy in this region was 3–18 km. A...

[1]  James C. McWilliams,et al.  The vortices of two-dimensional turbulence , 1990, Journal of Fluid Mechanics.

[2]  S. Rintoul,et al.  Cold-core anomalies at the subantarctic front, south of Tasmania , 2004 .

[3]  Hao Zhou,et al.  Wave height measurement in the Taiwan Strait with a portable high frequency surface wave radar , 2015, Acta Oceanologica Sinica.

[4]  D. Siegel,et al.  Linking kinematic characteristics and high concentrations of small pelagic fish in a coastal mesoscale eddy , 2015 .

[5]  P. Richardson,et al.  Caribbean current variability and the influence of the Amazon and Orinoco freshwater plumes , 2007 .

[6]  Gerik Scheuermann,et al.  Clifford convolution and pattern matching on vector fields , 2003, IEEE Visualization, 2003. VIS 2003..

[7]  J. Font,et al.  Identification of Marine Eddies from Altimetric Maps , 2003 .

[8]  Hiroyasu Hasumi,et al.  Ocean modeling in an eddying regime , 2008 .

[9]  H. Kawamura,et al.  Review on current and seawater volume transport through the Taiwan Strait , 2010 .

[10]  Hao Zhou,et al.  Portable High Frequency Surface Wave Radar OSMAR-S , 2015 .

[11]  Patrice Klein,et al.  Can oceanic submesoscale processes be observed with satellite altimetry? , 2010 .

[12]  J. Morell,et al.  Characterization of mesoscale eddies and detection of submesoscale eddies derived from satellite imagery and HF radar off the coast of southwestern Puerto Rico , 2015, OCEANS 2015 - MTS/IEEE Washington.

[13]  Xiongbin Wu,et al.  Spatial distribution characteristics of surface tidal currents in the southwest of Taiwan Strait , 2014, Journal of Ocean University of China.

[14]  Da Guo,et al.  Automated feature extraction in oceanographic visualization , 2004 .

[15]  Hao Zhou,et al.  Surface Current Characteristics in the Taiwan Strait Observed by High-Frequency Radars , 2017, IEEE Journal of Oceanic Engineering.

[16]  D. Chelton,et al.  Global observations of nonlinear mesoscale eddies , 2011 .

[17]  Wei Li,et al.  Heat, salt and volume transports by eddies in the vicinity of the Luzon Strait , 2012 .

[18]  Gengxin Chen,et al.  Mesoscale eddies in the South China Sea: Mean properties, spatiotemporal variability, and impact on thermohaline structure , 2011 .

[19]  Libe Washburn,et al.  Sub‐mesoscale coastal eddies observed by high frequency radar: A new mechanism for delivering nutrients to kelp forests in the Southern California Bight , 2005 .

[20]  Tommy D. Dickey,et al.  A Vector Geometry–Based Eddy Detection Algorithm and Its Application to a High-Resolution Numerical Model Product and High-Frequency Radar Surface Velocities in the Southern California Bight , 2010 .

[21]  S. K. Robinson,et al.  Coherent Motions in the Turbulent Boundary Layer , 1991 .

[22]  Clifford R. Merz,et al.  HF Radar Performance in a Low-Energy Environment: CODAR SeaSonde Experience on the West Florida Shelf , 2010 .

[23]  Biyang Wen,et al.  Wave extraction with portable high-frequency surface wave radar OSMAR-S , 2014, Journal of Ocean University of China.

[24]  Oscar Pizarro,et al.  Eddy characteristics in the eastern South Pacific , 2005 .

[25]  Einar Heiberg,et al.  Three-Dimensional Flow Characterization Using Vector Pattern Matching , 2003, IEEE Trans. Vis. Comput. Graph..

[26]  I. Sadarjoen,et al.  Selective visualization of vortices in hydrodynamic flows , 1998, Proceedings Visualization '98 (Cat. No.98CB36276).

[27]  Jinhee Jeong,et al.  On the identification of a vortex , 1995, Journal of Fluid Mechanics.

[28]  Frits H. Post,et al.  Detection, quantification, and tracking of vortices using streamline geometry , 2000, Comput. Graph..

[29]  Li Zi,et al.  Sea Surface Currents Detection at The Eastern China Sea by HF Ground Wave Radar OSMAR-S , 2009 .

[30]  Alexis Chaigneau,et al.  Mesoscale eddies off Peru in altimeter records: Identification algorithms and eddy spatio-temporal patterns , 2008 .

[31]  R. Bidigare,et al.  Physical dynamics and biological implications of a mesoscale eddy in the lee of Hawai'i : Cyclone Opal observations during E-Flux III , 2008 .

[32]  C. Amante,et al.  ETOPO1 arc-minute global relief model : procedures, data sources and analysis , 2009 .

[33]  Jingsong Yang,et al.  Three-dimensional properties of mesoscale eddies in the South China Sea based on eddy-resolving model output , 2015 .

[34]  Clifford R. Merz,et al.  Assessment of CODAR SeaSonde and WERA HF Radars in Mapping Surface Currents on the West Florida Shelf , 2014 .

[35]  Fangxin Fang,et al.  Evolution, movement and decay of warm-core Leeuwin Current eddies , 2003 .

[36]  Feng Nan,et al.  Three long‐lived anticyclonic eddies in the northern South China Sea , 2011 .

[37]  A. G. Zatsepin,et al.  Submesoscale eddies at the caucasus Black Sea shelf and the mechanisms of their generation , 2011 .

[38]  Clifford R. Merz,et al.  Effect of Radio Frequency Interference (RFI) Noise Energy on WERA Performance Using the "Listen Before Talk" Adaptive Noise Procedure on the West Florida Shelf , 2015 .

[39]  Frits H. Post,et al.  Geometric Methods for Vortex Extraction , 1999, VisSym.

[40]  Li Li,et al.  Anticyclonic rings from the Kuroshio in the South China Sea , 1998 .

[41]  F. Chavez,et al.  Calibration and Validation of Direction-Finding High-Frequency Radar Ocean Surface Current Observations , 2006, IEEE Journal of Oceanic Engineering.

[42]  Yuping Guan,et al.  Eddy analysis in the subtropical zonal band of the North Pacific Ocean , 2012 .

[43]  Guihua Wang,et al.  Mesoscale eddies in the South China Sea observed with altimeter data , 2003 .

[44]  J. Morell,et al.  Cyclonic eddy entrains Orinoco River Plume in eastern Caribbean , 2004 .

[45]  Sung Yong Kim,et al.  Observations of submesoscale eddies using high-frequency radar-derived kinematic and dynamic quantities , 2010 .

[46]  Selective visualization of vortices in hydrodynamic flows , 1998 .