Empirical Mode Decomposition of the atmospheric wave field

• Published in: Annales geophysicae (1988) Vol. 25; no. 2; pp. 375 - 384
• Main Authors: MCDONALD, A. J, BAUMGAERTNER, A. J. G, FRASER, G. J, GEORGE, S. E, MARSH, S
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau European Geophysical Society 01-01-2007; Copernicus GmbH; European Geosciences Union; Copernicus Publications
• Subjects: Comparative analysis; Earth Sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Monte Carlo methods; Ocean, Atmosphere; Physics of the high neutral atmosphere; Physics of the ionosphere; Physics of the magnetosphere; Rossby waves; Sciences of the Universe; Antarctica, Victoria Land, Ross I., Scott Base; Antarctica; time series analysis; Frequency modulation; Wind field; Waves and tides; Monte Carlo analysis; Amplitude modulation; Wave interaction; Internal gravity wave; Non linear phenomenon; Hilbert transformation; Atmospheric dynamics; Meteorology and atmospheric dynamics Middle atmosphere dynamics; Wavelet transformation; Gravity wave; winds; White noise; Wind wave; Planetary wave; Instruments and techniques; Atmospheric wave
• ISSN: 0992-7689; 1432-0576; 1432-0576
• DOI: 10.5194/angeo-25-375-2007

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.