Analysis of non-stationary vector fields using wavelet transforms

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Citations (Scopus)

Abstract

Fast Fourier transforms (FFT) and empirical orthogonal functions (EOF) have been widely applied to coastal zone current measurements. However riverine tides, estuarine outflows, and eddies, exhibit non-stationary characteristics which invalidate the basic assumptions of these methods. Wavelet analysis techniques can be used to determine the temporal evolution of ocean current variance over a range of frequency scales and therefore can provide an improved understanding of event-driven dynamics. To investigate the characteristics of this type of analysis, a simulated vortex was advected through a region consistent with a High-Frequency (HF) radar domain. Morlet continuous-wavelet transforms, bi-orthogonal discrete wavelet transforms, FFTs, EOFs and digital filtering techniques were applied to multiple vector time-series collected within the simulation domain. The stationary spectral analysis methods did not resolve the eddy well due to the distribution of the energy throughout the observation period. Band-pass filtering of each point created spurious anti-cyclonic eddy motions both preceding and following the simulated eddy. Morlet wavelets were shown to localize the vortex energy in both space and time, with a characteristic dipole pattern due to the axis of clockwise/counterclockwise rotational symmetry along the eddy path. Morlet and bi-orthogonal wavelet transforms were then applied to measurements from a HF Doppler radar deployed off the lower Florida Keys in May, 1994 when several sub-mesoscale eddies were observed. The wavelet energy demonstrated the characteristic dipole observed in the simulations, although little advection was observed in the real data. This is perhaps due to the generation and decay of many sub-mesoscale eddies within the OSCR domain during this period. Reconstruction using discrete wavelets successfully eliminated random noise from the surface current fields without distorting the observed vortex.

Original languageEnglish (US)
Title of host publicationOceans Conference Record (IEEE)
PublisherIEEE
Pages1521-1527
Number of pages7
Volume3
StatePublished - 2000
EventOceans 2000 - Providence, RI, USA
Duration: Sep 11 2000Sep 14 2000

Other

OtherOceans 2000
CityProvidence, RI, USA
Period9/11/009/14/00

Fingerprint

wavelet
transform
eddy
vortex
mesoscale eddy
energy
Doppler radar
wavelet analysis
temporal evolution
spectral analysis
Fourier transform
simulation
coastal zone
symmetry
analysis
advection
tide
outflow
radar
time series

ASJC Scopus subject areas

  • Oceanography

Cite this

Haus, B. K., & Graber, H. C. (2000). Analysis of non-stationary vector fields using wavelet transforms. In Oceans Conference Record (IEEE) (Vol. 3, pp. 1521-1527). IEEE.

Analysis of non-stationary vector fields using wavelet transforms. / Haus, Brian K; Graber, Hans C.

Oceans Conference Record (IEEE). Vol. 3 IEEE, 2000. p. 1521-1527.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Haus, BK & Graber, HC 2000, Analysis of non-stationary vector fields using wavelet transforms. in Oceans Conference Record (IEEE). vol. 3, IEEE, pp. 1521-1527, Oceans 2000, Providence, RI, USA, 9/11/00.
Haus BK, Graber HC. Analysis of non-stationary vector fields using wavelet transforms. In Oceans Conference Record (IEEE). Vol. 3. IEEE. 2000. p. 1521-1527
Haus, Brian K ; Graber, Hans C. / Analysis of non-stationary vector fields using wavelet transforms. Oceans Conference Record (IEEE). Vol. 3 IEEE, 2000. pp. 1521-1527
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