Using non-decimated wavelet decomposition to analyse time variations of North Atlantic Oscillation, eddy kinetic energy, and Ukrainian precipitation

Loboda, N. S.; Глушков, А. В.; Khokhlov, V. N.; Lovett, L.

doi:10.1016/j.jhydrol.2005.02.029

Cited by 30 publications

(13 citation statements)

References 28 publications

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“…As stated by Torrence (1997), wavelet analysis provides an unbiased method of examining the variations in variance of a time series compared to the biased method of the windowed Fourier transform (Kaiser, 1994). According to Loboda et al (2006), wavelets have brought a revolution in both theory and practice for the identification of non‐stationary signals and the study of co‐variability of various time series in frequency and time domains. We apply the statistical tests developed by Torrence and Compo (1998).…”

Section: Methodsmentioning

confidence: 99%

Power of teleconnection patterns on precipitation and streamflow variability of upper Medjerda Basin

Ouachani

Bargaoui

Ouarda

2011

Intl Journal of Climatology

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ABSTRACT:The potential impact of large-scale climate patterns of El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation (PDO) in modulating precipitation regimes across the upper Medjerda River Basin in northern Tunisia is assessed. As the case study is located in the Mediterranean region (North Africa), the regional Mediterranean Oscillation (MOAC) and Western Mediterranean Oscillation (WeMO) are also investigated. Six precipitation time series are also observed. Strong correlations are identified between ENSO and precipitation series at lag −2 years. Extreme ENSO years are reflected in the precipitation as periods of severe water deficit or excess. Wavelet spectra driven to seasonal precipitation reveal that precipitation is organized in preferred bands with distinct activities in each scale band, and that most of the precipitation variance is explained by the 2-8-year scales. Using cross-wavelet analysis, climate patterns that are most associated with precipitation variability are identified. The analysis demonstrates also that precipitations are simultaneously controlled by different climate patterns. Particularly, the influence of ENSO on precipitation is stronger as well as that of PDO and MO. Results indicate that precipitation variability at the upper Medjerda River Basin is associated with global-scale ENSO processes at the annual as well as seasonal time scales and is aligned with changing phase difference between periods. Moreover, separation of annual precipitation into two seasons reveals statistically significant associations between El Niño and La Niña phases of ENSO with dry and wet seasonal precipitation, respectively. Complementing this, three streamflow records with length up to 104 years are used, and relationships with rainfall series are analysed using wavelets. A strong coherence between rainfall and streamflow observations is found and justifies undertaking the study of climate-streamflow relationships where ENSO exhibits potential impacts on annual streamflows.

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Section: Methodsmentioning

confidence: 99%

Power of teleconnection patterns on precipitation and streamflow variability of upper Medjerda Basin

Ouachani

Bargaoui

Ouarda

2011

Intl Journal of Climatology

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“…In particular, the continuous wavelet transform (CWT) was applied to determine if a time series shows a nonstationary behavior at different frequencies or periods. The nonstationarity of the NAO has been studied before using wavelet analysis [ Appenzeller et al , 1998; Loboda et al , 2006; Massei et al , 2007], but here we applied the method to monthly instead of annual means, which reveals the NAO's dominant mode of variability on a monthly time scale. Moreover, we also applied the CWT to the sulfate AOD for the period 1979–2008.…”

Section: Methodsmentioning

confidence: 99%

Decadal variability of aerosol optical depth in Europe and its relationship to the temporal shift of the North Atlantic Oscillation in the realm of dimming and brightening

et al. 2011

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[1] Long-term aerosol optical depth (AOD) over Europe was analyzed from the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model from . In particular, we studied the decadal sulfate AOD variability caused by large sulfur emissions from anthropogenic sources in Europe with a peak in [1988][1989]. Simulated annual means from 1985-2007 over the continent showed statistically significant declines of 69% and a maximum of 75% in eastern Europe. Seasonally, greatest variations occurred during winter and spring followed by summer and autumn. The decrease in AOD agrees with the increase in the annual, spring, and summer mean solar radiation in Europe after the mid-1980s as well as surface-based AOD measurements. However, the long-term AOD variability does not explain the trends found in solar radiation during winter and autumn, which may be due to the contribution from the North Atlantic Oscillation (NAO) and associated cloud cover. We also investigated a possible link between sulfate AOD and NAO and found a statistically significant correlation of −0.77 in winter for Europe. Wavelet coherence analysis revealed a strong and significant antiphase relationship around 1 year that was most pronounced in the late 1980s. Cross-correlation analysis showed a seasonal dependence of sulfate AOD and NAO with negative correlation during winter and positive during summer. This analysis may help explain the seasonal decadal variability of surface solar radiation and whether sulfate aerosols have contributed to the large positive trend of the NAO during the 1980s. However, the cause and effect relationship between sulfate aerosols and NAO remains unclear.Citation: Chiacchio, M., T. Ewen, M. Wild, M. Chin, and T. Diehl (2011), Decadal variability of aerosol optical depth in Europe and its relationship to the temporal shift of the North Atlantic Oscillation in the realm of dimming and brightening,

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“…It reveals the completion of time–scale representation of localized frequency information and transient phenomena occurring at different time scales. The literature indicates that wavelet analysis is useful in the investigation of periodic phenomena and leads to precise results especially in the temporal variability of processes (Labat, ; Wang et al ., ; Loboda et al ., ). For the annual runoff time series f ( t ), the continuous wavelet transform is calculated as

W_{f} (a, b) = {(||, a)}^{- \frac{1}{2}} \int_{- \infty}^{+ \infty} f true(t true) \overset{ψ}{true} ((), \frac{t - b}{a}) d t

where W f ( a , b ) is the wavelet transform coefficient, ψ ( t ) is the mother wavelet, a is a scale parameter and b is a time parameter.…”

Section: Methodsmentioning

confidence: 99%

Characteristics of annual runoff variation in major rivers of China

Wang

et al. 2011

Hydrological Processes

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Abstract:The statistical properties of annual runoff in major rivers of China are studied based on the theory of stochastic process and technology of time series analysis. These properties include the characteristics of intra-annual and inter-annual variations of runoff, trends, abrupt changes and periodicities. The new findings from the intensive calculations and appropriate analysis of data in longer period are as follows: (i) compared with the nonuniformity of intra-annual runoff before 1980, the nonuniformity of intra-annual runoff in China generally decreased after 1980, except for Huaihe River and Songhua River; (ii) compared with the annual runoff before 1980, the annual runoff in China generally decreased after 1980 except for WangJiaba station in Huaihe River and Ha-Erbin station in Songhua River; the frequency of continuous low flow and continuous high flow in Haihe River and the downstream of Yellow River is higher than those in other rivers in China; (iii) annual runoff shows a downward trend in major rivers of China especially in Haihe River, Liao River and the midstream and downstream of Yellow River; (iv) there exist certain abrupt changes of annual runoff in major rivers of China; the abrupt change-points are different among different river basins; and (v) almost periodicities of annual runoff sequences in major rivers of China are generally 20 years below, that is, 3~7 and 12~20 years. The reasons for these changes are mainly caused by climate change and human activities.

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Using non-decimated wavelet decomposition to analyse time variations of North Atlantic Oscillation, eddy kinetic energy, and Ukrainian precipitation

Cited by 30 publications

References 28 publications

Power of teleconnection patterns on precipitation and streamflow variability of upper Medjerda Basin

Power of teleconnection patterns on precipitation and streamflow variability of upper Medjerda Basin

Decadal variability of aerosol optical depth in Europe and its relationship to the temporal shift of the North Atlantic Oscillation in the realm of dimming and brightening

Characteristics of annual runoff variation in major rivers of China

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