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TECHNICAL PAPERS

Modeling Tidal Current Profiles by Means of Empirical Orthogonal Functions

[+] Author and Article Information
C. Guedes Soares

Unit of Marine Technology and Engineering, Technical University of Lisbon, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugalguedess@mar.ist.utl.pt

S. N. Neves

Unit of Marine Technology and Engineering, Technical University of Lisbon, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugalsneves@mar.ist.utl.pt

J. Offshore Mech. Arct. Eng 128(3), 184-190 (Dec 13, 2005) (7 pages) doi:10.1115/1.2199564 History: Received September 24, 2004; Revised December 13, 2005

The method of empirical orthogonal functions (EOFs) is used to model vertical velocity profiles of the current. The whole current field is decomposed into time series of along and cross-slope velocity components. These time series are then filtered keeping only the frequency bands corresponding to the most significant peaks of the current power density spectra, which in most cases correspond to the main semidiurnal and long period tidal components. New time series are originated containing only filtered current. For each one of these filtered time-series, EOFs and the respective principal components are then derived. The derivation of empirical orthogonal functions make possible the separation of the local flow variability into a few modes of variance. In a general way, the along-slope flow may be described mainly as barotropic, although the baroclinic contribution tends to reach some significance in the flow crossing the shelf slope.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Location of the observations, bathymetry, and local surface circulation

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Figure 2

Distribution of power spectral density versus frequency in Series C-90. Depths 47m and 237m.

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Figure 3

Vertical profile of EOFs associated with the first three modes of variance for the along and cross-slope components of the residual current velocity for M2 tide oscillation. Series C86-2.

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Figure 4

Vertical profile of EOFs associated with the first three modes of variance for the along and cross-slope components of the residual current velocity for S2 tide oscillation. Series C90.

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Figure 5

Vertical profile of EOFs associated with the first three modes of variance for the along and cross-slope components of the residual current with period between 2 and 4 days. Series C90.

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Figure 6

Vertical profile of EOFs associated with the first three modes of variance for the along and cross-slope components of the residual current with period between 14 and 16 days. Series C86-1.

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Figure 7

Time modulation of first mode for M2 tide current. Series C86-1.

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Figure 8

Time modulation of first mode for residual current with period between 14 and 16 days. Series C86-1.

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