References of "Mabille, Georges"
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See detailAnalyse de la variabilité naturelle du climat : application à l’aide des ondelettes
Mabille, Georges ULg

Doctoral thesis (2014)

Ce travail a pour but de mettre en évidence des cycles méconnus et cachés de la transformée de Fourier dans les séries temporelles liées au climat. Les périodes recherchées, à l’aide de l’outil ondelettes ... [more ▼]

Ce travail a pour but de mettre en évidence des cycles méconnus et cachés de la transformée de Fourier dans les séries temporelles liées au climat. Les périodes recherchées, à l’aide de l’outil ondelettes développé à l’Institut de Mathématique de l’Université de Liège, sont de l’ordre de quelques dizaines de mois. [less ▲]

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See detailConfidence levels for the cycles found in climatic data
Mabille, Georges ULg

Scientific conference (2014, June 06)

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See detailDécouverte d’un nouveau cycle du climat
Mabille, Georges ULg; Nicolay, Samuel ULg

Article for general public (2012)

L'outil mathématique "transformée en ondelettes" est appliqué ici à des séries de températures de l'air au sol et met en évidence un cycle de l'ordre de 30 mois. Ce cycle s’observe sur une part importante ... [more ▼]

L'outil mathématique "transformée en ondelettes" est appliqué ici à des séries de températures de l'air au sol et met en évidence un cycle de l'ordre de 30 mois. Ce cycle s’observe sur une part importante de la surface de la planète. [less ▲]

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See detailÉtude fréquentielle de données via la transformée en ondelette : application aux cycles climatiques
Mabille, Georges ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg et al

in Bulletin de la Société Géographique de Liège (2012), 58

Understanding the climate requires a complex study of time series connected to weather parameters. The climatologist frequently applies signal processing tools and often uses the harmonic analysis and the ... [more ▼]

Understanding the climate requires a complex study of time series connected to weather parameters. The climatologist frequently applies signal processing tools and often uses the harmonic analysis and the Fourier transform. This article is dedicated to the description of a new tool, elaborated by mathematicians, which completes the outfit of intruments intended for signal analysis. The scale spectrum, which synthetizes a part of the information supplied by the wavelet transform, possesses the property to reveal pseudo-cycles which evolves around an average period. When applied to air surface temperature time series obtained from more than one hundred weather stations, to reanalysis data and to climatic indices which characterize the tropospheric flows, the wavelet transforms and the scale spectra reveal cycles with periods close to 30 months and 42 months. The Solar parameters analysis also leads to the existence of pseudo-cycles with frequencies corresponding to those found in the temperature time series and climatic indices. [less ▲]

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See detailA statistical validation for the cycles found in air temperature data using a Morlet wavelet-based method
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

in Nonlinear Processes in Geophysics (2010), 17

Recently, new cycles, associated with periods of 30 and 43 months, respectively, have been observed by the authors in surface air temperature time series, using a wavelet-based methodology. Although many ... [more ▼]

Recently, new cycles, associated with periods of 30 and 43 months, respectively, have been observed by the authors in surface air temperature time series, using a wavelet-based methodology. Although many evidences attest the validity of this method applied to climatic data, no systematic study of its efficiency has been carried out. Here, we estimate confidence levels for this approach and show that the observed cycles are significant. Taking these cycles into consideration should prove helpful in increasing the accuracy of the climate model projections of climate change and weather forecast. [less ▲]

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See detailMulti-Months Cycles Observed in Climatic Data
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

in Simard, Suzanne (Ed.) Climate Change and Variability (2010)

Climatic variations happen at all time scales and since the origins of these variations are usually of very complex nature, climatic signals are indeed chaotic data. The identification of the cycles ... [more ▼]

Climatic variations happen at all time scales and since the origins of these variations are usually of very complex nature, climatic signals are indeed chaotic data. The identification of the cycles induced by the natural climatic variability is therefore a knotty problem, yet the knowing of these cycles is crucial to better understand and explain the climate (with interests for weather forecasting and climate change projections). Due to the non-stationary nature of the climatic time series, the simplest Fourier-based methods are inefficient for such applications (see e.g. Titchmarsh (1948)). This maybe explains why so few systematic spectral studies have been performed on the numerous datasets allowing to describe some aspects of the climate variability (e.g. climatic indices, temperature data). However, some recent studies (e.g. Matyasovszky (2009); Paluš & Novotná (2006)) show the existence of multi-year cycles in some specific climatic data. This shows that the emergence of new tools issued from signal analysis allows to extract sharper information from time series. Here, we use a wavelet-based methodology to detect cycles in air-surface temperatures obtained from worldwide weather stations, NCEP/NCAR reanalysis data, climatic indices and some paleoclimatic data. This technique reveals the existence of universal rhythms associated with the periods of 30 and 43 months. However, these cycles do not affect the temperature of the globe uniformly. The regions under the influence of the AO/NAO indices are influenced by a 30 months period cycle, while the areas related to the ENSO index are affected by a 43 months period cycle; as expected, the corresponding indices display the same cycle. We next show that the observed periods are statistically relevant. Finally, we consider some mechanisms that could induce such cycles. This chapter is based on the results obtained in Mabille & Nicolay (2009); Nicolay et al. (2009; 2010). [less ▲]

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See detailDe la démarche scientifique face aux changements climatiques
Nicolay, Samuel ULg; Mabille, Georges ULg

Article for general public (2009)

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See detailCycles in the Temperature Data Are Induced by the Sun
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

Poster (2009, April)

The presence of two cycles of period of 30 and 42 months approximatively has been observed in temperature records and climatic indices. Moreover, it has been shown that these cycles are statistically ... [more ▼]

The presence of two cycles of period of 30 and 42 months approximatively has been observed in temperature records and climatic indices. Moreover, it has been shown that these cycles are statistically significant. Here we outline the role played by the Sun in the presence of these cycles, observed in time series. To do so, we use IPCC AR4 climatic models, sunspot number data and the Morlet wavelet method. [less ▲]

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See detailConfidence Levels for the Cycles Found in Air Temperature Data
Mabille, Georges ULg; Fettweis, Xavier ULg; Erpicum, Michel ULg et al

Poster (2009, April)

Recently, new cycles have been observed in air temperature data and proxy series using a wavelet-based methodology. Although many evidences attest the validity of this method applied to climatic data, no ... [more ▼]

Recently, new cycles have been observed in air temperature data and proxy series using a wavelet-based methodology. Although many evidences attest the validity of this method applied to climatic data, no systematic study of its efficiency has been carried out. Here, we estimate the confidence levels for this approach and show that the observed cycles are significant. [less ▲]

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See detailCycles found in air temperature data and proxy series using the Morlet wavelet method
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

Scientific conference (2009, February 25)

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See detailNew cycles found in air temperature data and proxy series using the Morlet wavelet method
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

Conference (2009, January 13)

We use the wavelet transform to detect cycles in air temperature data and proxy series

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See detailMulty-year cycles observed in air temperature data and proxy series
Mabille, Georges ULg; Nicolay, Samuel ULg

in European Physical Journal. Special Topics (2009), 174

First, palaeoclimatic time series are analyzed under the lens of the continuous wavelet transform. Two cycles, of period 30 and 43 months respectively, are detected in millennial temperature ... [more ▼]

First, palaeoclimatic time series are analyzed under the lens of the continuous wavelet transform. Two cycles, of period 30 and 43 months respectively, are detected in millennial temperature reconstructions. These rhythms correspond to the ones detected in weather station temperature records in a previous study of the authors. It is then showed that most parts of the globe are affected by at least one of the two cycles. Their relationship with the main climatic indices is also investigated, as well as the statistical significance of the observations. [less ▲]

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See detail30 and 43 months period cycles found in air temperature time series using the Morlet wavelet
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

in Climate Dynamics (2009), 33

A wavelet-based methodology is applied to relevant climatic indices and air temperature records and allow to detect the existence of unexpected cycles. The scale spectrum shows the presence of two cycles ... [more ▼]

A wavelet-based methodology is applied to relevant climatic indices and air temperature records and allow to detect the existence of unexpected cycles. The scale spectrum shows the presence of two cycles of about 30 and 43 months, respectively, in the air–temperature time series, in addition to the well-known cycles of 1 day and 1 year. The two cycles do not affect the globe uniformly: some regions seem to be more influenced by the period of 30 months (e.g. Europe), while other areas are affected by the period of 43 months (e.g. North-West of the USA). Similar cycles are found in the indices and the regions influenced by these indices: the NAO index and the Western Europe display a cycle of 30 months, while the cycle of 43 months can be found in the ENSO index and in regions where it is known to have an impact. [less ▲]

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See detailAnalysis of climatic conditions of wildfires in Belgium with an automatic daily atmospheric circulation patterns classification
Erpicum, Michel ULg; Fettweis, Xavier ULg; Mabille, Georges ULg

Conference (2008, October 02)

An automatic daily atmospheric circulation patterns classification was built using the geopotential heights of 850 hPa level from the ECMWF (re)analysis over the period 1958-2007. The classification is ... [more ▼]

An automatic daily atmospheric circulation patterns classification was built using the geopotential heights of 850 hPa level from the ECMWF (re)analysis over the period 1958-2007. The classification is based on a similarity index between two 850hPa geopotential maps centred on Belgium, taking into account the slope difference between both daily geopotential surfaces as well as the absolute geopotential difference between both surfaces. Wildfire occurrences are analysed in April and September together with monthly frequencies and persistences of daily atmospheric circulation patterns types as well as with monthly variability of weather climate conditions. [less ▲]

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See detailNew cycles found in air temperature data and proxy series
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

Conference (2008, October 01)

We apply the wavelet transform tool to detect unsuspected cycles in several climatic time series

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See detailSolar activity in connection with a 2.5 years periode cycle in air temperature time series using the Morlet wavelet method
Nicolay, Samuel ULg; Mabille, Georges ULg; Fettweis, Xavier ULg et al

Conference (2008, April 17)

The Morlet wavelet is applied to air temperature time series obtained from several weather stations and reveals the existence of a period cycle of 20-30 months since 1950, with an estimated amplitude of 0 ... [more ▼]

The Morlet wavelet is applied to air temperature time series obtained from several weather stations and reveals the existence of a period cycle of 20-30 months since 1950, with an estimated amplitude of 0.5 C. The origin of this period is investigated by computing the scale spectra associated to the principal indices that characterize air mass flows in the troposphere and the stratosphere, as well as the signals related to the sunspot number and the solar flux. Each analysed signal shows this period of approximatively 2.5 years. This suggests that the 2.5 years-cycle could be resulted from the solar activity. [less ▲]

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See detailAutomatic 1958-2007 daily weather pattern classification applied to an analysis of climatic conditions of wildfires in eastern Belgium
Erpicum, Michel ULg; Fettweis, Xavier ULg; Mabille, Georges ULg et al

Poster (2008, April)

The daily atmospheric circulation patterns classification is founded on a 100 km regular grid centred on Belgium. The geopotential heights of 500, 850 and 1000 hPa levels were extracted <br />from the ERA ... [more ▼]

The daily atmospheric circulation patterns classification is founded on a 100 km regular grid centred on Belgium. The geopotential heights of 500, 850 and 1000 hPa levels were extracted <br />from the ERA-40 database on the period 1958-2002 and from ECMWF operational analysis until the end of year 2007. The classification was based on a similarity index calculated on the orientation of exaggerated slopes of different daily geopotential fields. Wildfire occurrences were analyzed in April and September (which are the two months with the most frequent wildfire-days in Belgium) together with monthly frequencies and persistences of daily atmospheric circulation pattern classes as well as with yearly variability of weather climate conditions. [less ▲]

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See detailCirculations atmosphériques et anomalies de fonte à la surface de la calotte glaciaire du Groenland
Fettweis, Xavier ULg; Mabille, Georges ULg; Erpicum, Michel ULg

in Bulletin de la Société Géographique de Liège (2008), 51

With the aim to study the impact of the 500hPa general circulation on the Greenland ice sheet surface melt simulated by the regional climate model MAR, we developed a new Circulation Type Classification ... [more ▼]

With the aim to study the impact of the 500hPa general circulation on the Greenland ice sheet surface melt simulated by the regional climate model MAR, we developed a new Circulation Type Classification (CTC) based on the 500hPa geopotential height from the ECMWF (re)analysis over the period 1958-2007. This CTC shows that the dominant mode of the regional atmospheric variability around the Greenland is linked to the North Atlantic Oscillation (NAO) and that the surface anomalies are highly correlated to the general circulation. It explains also why a record surface melt was observed during the summer 2007. The 27th August of 2003, where the temperature was 10°C higher than the normal, is the consequence of an almost unique 500 hPa circulation in the 50 last years. [less ▲]

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See detailAnalyse des débits de la Warche aux barrages de Butgenbach et de Robertville
Assani, A. A.; Petit, François ULg; Mabille, Georges ULg

in Bulletin de la Société Géographique de Liège (1999)

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See detailPrécipitations atmosphériques et altitude. Prélude à une cartographie des montants annuel et mensuels en Belgique
Alexandre, Jean ULg; Erpicum, Michel ULg; Mabille, Georges ULg et al

in Publications de l'Association Internationale de Climatologie (1998), 11

Detailed reference viewed: 98 (45 ULg)