Low frequency modes and their link with summer monsoon activity described by wavelet analysis throughout India

Combined wavelet and principal component analysis (WEof) of a scale-oriented model of coastal ocean gravity waves

“…ω = 8.3 × 10 −2 h −1 for Source 1 (Mallat, 2001). Two processes separated by a frequency difference smaller than ω cannot be efficiently identified in this frequency band (see also Ouergli, 2000). For the present experiment, the Heisenberg box criterion associated with the analysis frequency is well suited to frequency band localization.…”

“…Moving from process-oriented modeling to scale-oriented modeling raises a large number of new problems including the recognition and reconstruction of coherent dynamical structures. Following Wang et al (2000) and Ouergli (2000), we propose to combine Principal Component Analysis (PCA) (Preisendorfer et al, 1981) and time-frequency wavelet analysis (Farge, 1992) to study the generation and propagation of fundamental ocean transient processes such as gravity waves. The so-called WEof technique is thus a combination of spatial PCA and time-frequency analysis.…”

“…The WEof method presented in this study is an extension of the analysis technique used by Wang et al (2000) where the computation of dominant modes from the vertical temperature profile gives the internal wave characteristics. Ouergli (2000) further analyzes daily sea-level pressure maps to study low-frequency modes of the summer Indian monsoon. Our approach is 3D in space and includes multivariate analysis of both surface elevation and vertical velocities.…”