Temporally Varying Mesoscale Eddy Characteristics in the California Current System Identified from RAFOS Floats
DOI:
https://doi.org/10.1590/Keywords:
Empirical mode decomposition, Eddy radial scale, Eddy velocity scale, Eddy rossby number, Eddy-current kinetic energy ratioAbstract
The SOund Fixing And Ranging (RAFOS) floats were deployed by the Naval Postgraduate School (NPS) near California coast from 1992 to 2004 at depth between 150 and 600 m (http://www.oc.nps.edu/npsRAFOS/). Each drifter trajectory is adaptively decomposed using the empirical mode decomposition (EMD) into low-frequency (non-diffusive, i.e., current) and high-frequency (diffusive, i.e., eddies) components. The identified eddies are mostly anticyclonic with total 203 anticyclonic and 36 cyclonic spirals. Eddy characteristics are determined from the time series of individual RAFOS float trajectory. They are the current velocity scale, eddy radial scale, eddy velocity scale, eddy Rossby number, and eddy-current kinetic energy ratio. The California Current System is found an eddy-rich system with the overall eddy-current kinetic energy ratio of 1.78. It contains submesoscale and mesoscale eddies. The horizontal length scale of 10 km is a good threshold of the eddy radial scale (Leddy) to separate the two kinds of eddies. The mean eddy Rossby number is 0.72 for the submesoscale eddies and 0.06 for the mesoscale eddies. The current-eddy kinetic energy ratio is similar between submesoscale and mesoscale eddies. This may imply similar current-eddy kinetic energy transfer for submesoscale and mesoscale eddies. Statistical characteristics and interannual variability of current velocity scale and eddy characteristic parameters are also presented.
References
BAUER, S., SWENSON, S., GRIFFA, A., MARIANO, A. J. & OWENS, K. 1998. Eddy-mean decomposition and eddy-diffusivity estimates in the tropical Pacific Ocean. Journal of Geophysical Research, 103(C13), 855-871.
CHU, P. C. 2018. Steepest ascent low/non-low frequency ratio in empirical mode decomposition to separate deterministic and stochastic velocities from a single Lagrangian drifter. Journal of Geophysical Research, 123(3), 1708-1721, DOI: https://doi.org/10.1002/2017JC013500
» https://doi.org/10.1002/2017JC013500
CHU, P. C. & FAN, C. W. 2014. Accuracy progressive calculation of Lagrangian trajectory from gridded velocity field. Journal of Atmospheric and Oceanic Technology, 31(7), 1615-1627.
CHU, P. C., FAN, C. W. & HUANG, N. 2012. Compact empirical mode decomposition - an algorithm to reduce mode mixing, end effect, and detrend uncertainty. Advances in Adaptive Data Analysis, 4(3), 1250017, DOI: https://doi.org/10.1142/S1793536912500173
» https://doi.org/10.1142/S1793536912500173
CHU, P. C., FAN, C. W. & HUANG, N. 2014. Derivative-optimized empirical mode decomposition for the Hilbert-Huang transform. Journal of Computational and Applied Mathematics, 259(Pt A), 57-64.
CHU, P. C., IVANOV, L. M., KORZHOVA T. P., MARGOLINA, T. M. & MELNICHENKO, O. M. 2003a. Analysis of sparse and noisy ocean current data using flow decomposition. Part 1: theory. Journal of Atmospheric and Oceanic Technology, 20(4), 478-491.
CHU, P. C., IVANOV, L. M., KORZHOVA T. P., MARGOLINA, T. M. & MELNICHENKO, O. M. 2003b. Analysis of sparse and noisy ocean current data using flow decomposition. Part 2: application to Eulerian and Lagrangian data. Journal of Atmospheric and Oceanic Technology, 20, 492-512.
CHU, P. C., IVANOV, L. M. & MELNICHENKO, O. M. 2005. Fall-winter current reversals on the Texas-Louisiana continental shelf. Journal of Physical Oceanography, 35, 902-910.
CHU, P. C., IVANOV, L. M., MELNICHENKO, O. V. & WELLS, N. C. 2007. On long baroclinic Rossby waves in the tropical North Atlantic observed from profiling floats. Journal of Geophysical Research, 112(C5), C05032, DOI: https://doi.org/10.1029/2006JC003698
» https://doi.org/10.1029/2006JC003698
COLLINS, C. A., GARFIELD, N., RAGO, T. A., RISERMILLER, F. W. & CARTER, E. 2000. Mean structure of the inshore countercurrent and California Undercurrent off Point Sur, California. Deep Sea Research Part II, 47, 765-782.
COLLINS, C. A., IVANOV, L. M., MELNICHENKO, O. B. & GARFIELD, N. 2004. California Undercurrent variability and eddy transport estimated from RAFOS float observations. Journal of Geophysical Research, 109(C5), DOI: https://doi.org/10.1029/2003JC002191
» https://doi.org/10.1029/2003JC002191
COLLINS, C. A., PAQUETTE, R. G. & RAMP, S. R. 1996. Annual variability of ocean currents at 350m depth over the continental slope off Point Sur, California, CalCOFI Report, 37 La Jolla: California Cooperative Oceanic Fisheries Investigations, pp. 257-263.
DAVIS, R. E. 1991. Observing the general circulation with floats. Deep Sea Research, 38(Suppl 1), S531-S571.
GARFIELD, N., COLLINS, C. A., PAQUETTE, R. G. & CARTER, E. I999. Lagrangian exploration of the California undercurrent, 1992-95. Journal of Physical Oceanography, 29, 560-583.
HUANG, N., SHEN, Z., LONG, S. R. WU, M. C., SMITH, H. H., ZHENG, Q., YEN, N., TUNG, C. C. & LIU, H. H. 1998. The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis. Proceedings of Royal Society London, 454, 903-995.
HUYER, A., BARTH, J. A., KOSRO, P. M., SHEARMAN, R. K. & SMITH, R. L. 1998. Upper-ocean water mass characteristics of the California Current, summer 1993. Deep Sea Research Part II: Topical Studies in Oceanography, 45(8-9), 1411-1442.
OBUKO, A. & EBBESMEYER, C. C. 1976. Determination of vorticity, divergence, and deformation rates from analysis of drogue observations. Deep Sea Research and Oceanographic Abstracts, 23(4), 349-352.
RIOS, R. A. & MELLO, R. F. 2016. Applying empirical mode decomposition and mutual information to separate stochastic and deterministic influences embedded in signals. Signal Processing, 118, 159-176.
RYPINA, I. I., KAMENKOVICH, I., BERLOFF, P. & PRATT, L. J. 2012. Eddy-induced particle dispersion in the near-surface North Atlantic. Journal of Physical Oceanography, 42(12), 2206-2228.
SIMPSON, J. J. & LYNN, R. J. 1990. A mesoscale eddy dipole in the off¬shore California Current. Journal of Geophysical Research, 95(C8), 13009-13022.
Downloads
Published
Issue
Section
License
Ocean and Coastal Research is an open-access journal available through SciELO (Scientific Electronic Library Online).
Ocean and Coastal Research journal title abbreviation is Ocean Coast. Res. and should be used in footnotes, references, and bibliographic entries.
All Ocean and Coastal Research scientific articles are freely available without charge to the user or institution. In accordance with the BOAI definition of open access, all contents are available to readers free of charge. Users may read, download, copy, and link to the full texts of the articles. They may be used for any lawful purpose without prior authorization from the publisher or the author, as long as proper credit is given to the original publication.
All Ocean and Coastal Research published scientific articles receive an individual Digital Object Identifier (DOI) persistent digital document identification.
All the content of the journal, except where otherwise noted, is licensed under a Creative Commons License type BY. Authors retain the copyright and full publishing rights without restrictions.
More information on intellectual property can be found here and on Scielo's Open Acess Statement.
Ocean and Coastal Research is listed in Publons and reviewers and editors can add their verified peer review and editing history to their Publons profile.
Ocean and Coastal Research is indexed in the Directory of Open Access Journals (DOAJ) and complies with principles of transparency and best practice for scholarly publications.
Ocean and Coastal Research is committed to the best standards in open-access publishing by adopting ethical and quality standards throughout the publishing process - from initial manuscript submission to the final article publication. This ensures authors that their work will have visibility, accessibility, reputation, usage, and impact in a sustainable model of scholarly publishing.
