A new method for analysing nonlinear and non-stationary data has been developed. The key part of the method is the empirical mode decomposition method with which any complicated data set can be dec...

/pdf/the-empirical-mode-decomposition-and-the-hilbert-spectrum-qkmom366dy.pdf

The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis

Data Mining - Concepts and Techniques.

A new Ensemble Empirical Mode Decomposition (EEMD) is presented. This new approach consists of sifting an ensemble of white noise-added signal (data) and treats the mean as the final true result. Finite, not infinitesimal, amplitude white noise is necessary to force the ensemble to exhaust all possible solutions in the sifting process, thus making the different scale signals to collate in the proper intrinsic mode functions (IMF) dictated by the dyadic filter banks. As EEMD is a time–space analysis method, the added white noise is averaged out with sufficient number of trials; the only persistent part that survives the averaging process is the component of the signal (original data), which is then treated as the true and more physical meaningful answer. The effect of the added white noise is to provide a uniform reference frame in the time–frequency space; therefore, the added noise collates the portion of the signal of comparable scale in one IMF. With this ensemble mean, one can separate scales naturall...

/pdf/ensemble-empirical-mode-decomposition-a-noise-assisted-data-4htvj7tcuy.pdf

Ensemble empirical mode decomposition: a noise-assisted data analysis method

to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

Researches on the currents in the South China Sea (SCS) and the interaction between the SCS and its adjacent seas are reviewed Overall seasonal circulation in the SCS is cyclonic in winter and anticyclonic in summer with a few stable eddies The seasonal circulation is mostly driven by monsoon winds, and is related to water exchange between the SCS and the East China Sea through the Taiwan Strait, and between the SCS and the Kuroshio through the Luzon Strait Seasonal characteristics of the South China Sea Warm Current in the northern SCS and the Kuroshio intrusion to the SCS are summarized in terms of the interaction between the SCS and its adjacent seas

http://faculty.petra.ac.id/dwikris/docs/cvitae/docroot/html/www.terrapub.co.jp/journals/JO/pdf/5606/56060607.pdf

A Review on the Currents in the South China Sea: Seasonal Circulation, South China Sea Warm Current and Kuroshio Intrusion

Variabilities in sea-surface temperature and size of the Western Pacific Warm Pool were tracked with 10 years of satellite multichannel sea-surface temperature observations from 1982 to 1991. The results show that both annual mean sea-surface temperature and the size of the warm pool increased from 1983 to 1987 and fluctuated after 1987. Possible causes of these variations include solar irradiance variabilities, El Nino-Southern Oscillaton events, volcanic activities, and global warming.

http://science.sciencemag.org/content/sci/258/5088/1643.full.pdf

Temperature and Size Variabilities of the Western Pacific Warm Pool

[1] This study analyzes the effects of thermocline shoaling on the ocean internal wave (IW) generation in the north South China Sea (NSCS). Seven years of satellite synthetic aperture radar (SAR) images from 1995 to 2001 are used for the statistical analysis of IW occurrence, and field measurements of sea surface wind, sea state, and vertical temperature profiles are used for analyzing IW generation and SAR imaging conditions. Latitudinal distribution of IW packets shows that 22% of IW packets distributed in the east of 118E obviously originate from the Luzon Strait, and 78% of IW packets west of 118E may propagate from the east or evolve into the solitons originating from the east boundary owing to the fission effect of shoaling thermocline. The yearly distribution of IW occurrence frequencies reveals an interannual variability, implying that there are long-term and large-scale processes modifying the SAR-observed IW occurrence. The monthly SAR-observed IWoccurrence frequencies show that the high frequencies are distributed from April to July and reach a peak in June with a maximum frequency of 20%. The low occurrence frequencies are distributed in winter from December to February of next year with a minimum frequency of 1.5% in February. This study proposes that the IW generation needs the necessary and sufficient conditions: initial disturbance formation and wave amplitude growth. Owing to the dissipation effect on the initial disturbance, only fully grown waves have a chance to radiate out of the source region. A physical model and PKdVequation are adopted for analyzing the sufficient conditions for solitary IW amplitude growth. The results indicate that the thermocline shoaling provides the forcing to soliton amplitude growth, so that the soliton amplitude growth ratio (SAGR) serves as a decisive factor for the IW occurrence frequency. Theoretical analysis predicts a linear relation between the two. Application of theoretical models to field measurements in the Luzon Strait gives a correlation coefficient as high as 0.845 with a confidence level of 99% for months from March to November. The linear regression gives a correlation coefficient (R 2 ) of 0.6519 and a SAGR threshold (minimum) value of

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2006JC003551

Statistical and dynamical analyses of generation mechanisms of solitary internal waves in the northern South China Sea

Satellite observation of upwelling along the western coast of the South China Sea

TOPEX/Poseidon altimeter measurements along 16 ground tracks in the South China Sea from November 1992 to October 1997 were used to observe the seasonal variability of sea surface height (SSH). In winter (November, December, January, and February) the SSH images are generally characterized by a sea surface tilting downward toward the east. High sea levels on the western side of the sea have a little monthly change, and a low (minus) sea level peak is centered in the northeastern deep basin. In spring (March and April), a single high sea level peak (HP) centered at 14°N, 114°E becomes a dominant feature. In summer (May, June, July, and August) the SSH images show a sea surface tilting downward toward the west. The HP moves from 14°N, 114°E in May to the northwest of Luzon Island in July. Low sea levels are centered in the offshore of the northern and southern Vietnamese coast. In fall (September and October) the appearance of an eastward low sea level jet in the western basin between 12° and 14°N constitutes a major feature of the SSH images. These results are comparable with previous results and drifter measurements.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JC900001

Seasonal variability of sea surface height in the South China Sea observed with TOPEX/Poseidon altimeter data

[1] The wake of Green Island was investigated in the alongshore flowing Kuroshio east of Taiwan, where current speeds range from 1 to 1.5 ms–1. Vertical profiling with shipboard lowered acoustic Doppler current profiler and conductivity-temperature-depth profiler revealed sizable anomalies in flow and water characteristics in the lee of Green Island. Two different stages of wake evolution were observed from two shipboard surveys. In the first stage, a recirculation developed leeward of the island, followed by a wavy (wave-like) tail that resembled a weak vortex street. In the second stage, a cold eddy probably originating from the leeward side of the island showed up 14 km downstream of the island. The wake water was colder, saltier, higher in chlorophyll-a concentration, and produced isopycnal doming up to 60 m. In the recirculation area, the relative vorticity, either positive or negative, was 10 times of planetary vorticity, and the horizontal divergence or convergence was O (10–4 s–1) on average. Flow divergence and convergence in the wake were expected to form upwelling and downwelling zones, producing a vertical circulation that vertically displaces isotherms. High inverse Richardson number, produced by strong vertical shear of horizontal currents, was associated with intense overturning events in the wake. High vertical shear of horizontal currents drove the mixing. The dissipation rate of turbulent kinetic energy in the overturn regions is O (10–7–10–5) W Kg–1; the corresponding eddy diffusivity is O (10–3–10–1) m2 s–1. The wake water properties are vertically diffused via upwelling and turbulence and can be delivered downstream through eddy shedding or advection. The extent of downstream influence remains to be investigated.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/jgrc.20151

Chung-Ru Ho

Papers

Temperature and Size Variabilities of the Western Pacific Warm Pool

Statistical and dynamical analyses of generation mechanisms of solitary internal waves in the northern South China Sea

Satellite observation of upwelling along the western coast of the South China Sea

Seasonal variability of sea surface height in the South China Sea observed with TOPEX/Poseidon altimeter data

Kuroshio-induced wake in the lee of Green Island off Taiwan