Improvement of edge effect of the wavelet time-frequency spectrum: application to the length-of-day series

Zheng, Dong; Chao, Benjamin F.; Zhou, Yonghong; Yu, Nanhua

doi:10.1007/s001900050283

Cited by 32 publications

(15 citation statements)

References 7 publications

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“…The technique of time-frequency wavelet transform has been applied to address different issues in Earth sciences (e.g. Morlet et al, 1982;Chao and Naito, 1995;Lau and Weng, 1995;Torrence and Compo, 1998;Zheng et al, 2000). In the method of Morlet, the wavelet transform of a time series f (t) is defined as:…”

Section: Frequency Characteristics Of Temperature Variationsmentioning

confidence: 99%

Variations of the surface temperature in Hong Kong during the last century

Ding

Zheng

Yang

2002

Intl Journal of Climatology

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A statistical analysis has been applied to obtain a better understanding of the variations of the surface climate in Southeast Asia. In particular, we have depicted the detailed features of the changes in the surface air temperature of Hong Kong (HK) during the past 115 years. Analysis of the time-frequency spectra of the wavelet transform indicates that although seasonal variations account for most of the temperature variations, strong signals also exist on subseasonal, interannual, and interdecadal time scales. Though the strong seasonal cycle is marked by a minimum temperature in February (and then in January) and a maximum temperature in July (and then in August), strong variations on the subseasonal and interannual time scales occur mostly in February and then in March. It is also found that a rising tendency exists in the long-recorded temperature data, with a rate of 0.09-0.15°C per decade.Temperature variations in HK are strongly related to changes in the regional and remote atmospheric circulation on various time scales. The East Asian monsoon circulation is the main factor controlling the seasonal cycle and the subseasonal and interannual variations of the HK temperature during winter. The subseasonal and seasonal variations of the temperature are also associated with changes in the atmospheric circulation over the North Pacific, which is closely linked to the East Asian jet stream. Strong signals are also found in both this mid-latitude circulation and the El Niño-southern oscillation phenomenon when the interannual variability of the HK temperature is apparent.

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Section: Frequency Characteristics Of Temperature Variationsmentioning

confidence: 99%

Variations of the surface temperature in Hong Kong during the last century

Ding

Zheng

Yang

2002

Intl Journal of Climatology

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“…As has been pointed out in this paper, there is evidence to suggest that not only the frequency of loss events caused by TCs in the WNP but also the (normalised) property losses resulting from landfalling TCs are modulated by low-frequency climate variations in the Northwest Pacific region. Zheng et al (2000) present an interesting approach to reducing edge effects in the wavelet time-frequency spectrum by using a numerical method prior to the wavelet transform to extend the time series on both ends (see their paper for details). This could enhance their ability to reveal lowfrequency signals in the time series.…”

Section: Discussionmentioning

confidence: 99%

Tropical cyclone-related socio-economic losses in the western North Pacific region

Welker

Faust

2013

Nat. Hazards Earth Syst. Sci.

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Abstract. The western North Pacific (WNP) is the area of the world most frequently affected by tropical cyclones (TCs).However, little is known about the socio-economic impacts of TCs in this region, probably because of the limited relevant loss data. Here, loss data from Munich RE's NatCat-SERVICE database is used, a high-quality and widely consulted database of natural disasters. In the country-level loss normalisation technique we apply, the original loss data are normalised to present-day exposure levels by using the respective country's nominal gross domestic product at purchasing power parity as a proxy for wealth. The main focus of our study is on the question of whether the decadal-scale TC variability observed in the Northwest Pacific region in recent decades can be shown to manifest itself economically in an associated variability in losses. It is shown that since 1980 the frequency of TC-related loss events in the WNP exhibited, apart from seasonal and interannual variations, interdecadal variability with a period of about 22 yr -driven primarily by corresponding variations of Northwest Pacific TCs. Compared to the long-term mean, the number of loss events was found to be higher (lower) by 14 % (9 %) in the positive (negative) phase of the decadal-scale WNP TC frequency variability. This was identified for the period 1980-2008 by applying a wavelet analysis technique. It was also possible to demonstrate the same low-frequency variability in normalised direct economic losses from TCs in the WNP region. The identification of possible physical mechanisms responsible for the observed decadal-scale Northwest Pacific TC variability will be the subject of future research, even if suggestions have already been made in earlier studies.

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“…The leap-step time series analysis (LSTSA) model developed by Zheng et al (2000) is applied to reduce the edge effects in the MSF and wavelet analysis.…”

Section: Methods Of Analysismentioning

confidence: 99%

Multi-scale variation of the meridional movement of the western Pacific warm pool and its associated large-scale climate features

Zhou

Yang

Zheng

2016

Theor Appl Climatol

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In this study, we investigated variation of the meridional movement of the western Pacific warm pool (WPWP). The variation was measured by the central latitude (Clat) of the WPWP on various time scales. Its relationships with global sea surface temperature (SST), precipitation, and atmospheric circulation were examined by applying several advanced statistical methods. First, the techniques of wavelet analysis and least-square adjustment were used to depict the time-frequency features and the mean dominant oscillating time scales of the Clat. Then, a multi-stage filtering technique was applied to illustrate the related dominant oscillating signals. We also examined the time-frequency characteristics of the relationships between Clat and the leading modes of the Indo-Pacific oceans by employing a cross-covariance function analysis and a multiple moving-window method. The physical mechanisms for the relationships between Clat and the patterns of SST, precipitation, and atmospheric circulation were discussed. Results indicated that there is a weakening trend in the oscillation of Clat mainly because the quasi-annual oscillation of Clat increases in January-March and decreases in July-September. The semi-annual oscillation of Clat closely interacts with the westerly wind over the summer hemisphere of the tropical western Pacific Ocean and with the easterly wind over the winter hemisphere of the ocean. The interannual component of Clat corresponds to El Niño-Southern Oscillation and the Indian Ocean basin-wide warming or cooling with strengthened oscillations in the 1970s, and the lower-frequency component of Clat closely corresponds to the central Pacific type of El Niño from the 1990s.

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Improvement of edge effect of the wavelet time-frequency spectrum: application to the length-of-day series

Cited by 32 publications

References 7 publications

Variations of the surface temperature in Hong Kong during the last century

Variations of the surface temperature in Hong Kong during the last century

Tropical cyclone-related socio-economic losses in the western North Pacific region

Multi-scale variation of the meridional movement of the western Pacific warm pool and its associated large-scale climate features

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