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| Titel |
Empirical Mode Decomposition of the atmospheric wave field |
| VerfasserIn |
A. J. McDonald, A. J. G. Baumgaertner, G. J. Fraser, S. E. George, S. Marsh |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 25, no. 2 ; Nr. 25, no. 2 (2007-03-08), S.375-384 |
| Datensatznummer |
250015784
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| Publikation (Nr.) |
 copernicus.org/angeo-25-375-2007.pdf |
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| Zusammenfassung |
This study examines the utility of the Empirical Mode Decomposition (EMD)
time-series analysis technique to separate the horizontal wind field observed
by the Scott Base MF radar (78° S, 167° E) into its
constituent parts made up of the mean wind, gravity waves, tides, planetary
waves and instrumental noise. Analysis suggests that EMD effectively
separates the wind field into a set of Intrinsic Mode Functions (IMFs) which
can be related to atmospheric waves with different temporal scales. The
Intrinsic Mode Functions resultant from application of the EMD technique to
Monte-Carlo simulations of white- and red-noise processes are compared to
those obtained from the measurements and are shown to be significantly
different statistically. Thus, application of the EMD technique to the MF
radar horizontal wind data can be used to prove that this data contains
information on internal gravity waves, tides and planetary wave motions.
Examination also suggests that the EMD technique has the ability to highlight
amplitude and frequency modulations in these signals. Closer examination of
one of these regions of amplitude modulation associated with dominant periods
close to 12 h is suggested to be related to a wave-wave interaction
between the semi-diurnal tide and a planetary wave. Application of the
Hilbert transform to the IMFs forms a Hilbert-Huang spectrum which provides a
way of viewing the data in a similar manner to the analysis from a continuous
wavelet transform. However, the fact that the basis function of EMD is
data-driven and does not need to be selected a priori is a major
advantage. In addition, the skeleton diagrams, produced from the results of
the Hilbert-Huang spectrum, provide a method of presentation which allows
quantitative information on the instantaneous period and amplitude squared to
be displayed as a function of time. Thus, it provides a novel way to view
frequency and amplitude-modulated wave phenomena and potentially non-linear
interactions. It also has the significant advantage that the results obtained
are more quantitative than those resultant from the continuous wavelet
transform. |
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