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J. Gailhard - One of the best experts on this subject based on the ideXlab platform.

  • Streamflow variability over the 1881–2011 period in northern Québec: comparison of hydrological reconstructions based on tree rings and Geopotential Height field reanalysis
    Climate of the Past, 2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

  • streamflow variability over the 1881 2011 period in northern quebec comparison of hydrological reconstructions based on tree rings and Geopotential Height field reanalysis
    Climate of The Past, 2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

  • Streamflow variability over 1881–2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and on Geopotential Height field reanalysis
    2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Abstract. Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir to compare the obtained streamflow series and study the natural streamflow variability over the 1881–2011 period. This new reconstruction is based, not on natural proxies, but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall-runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, both in terms of monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows, and the other one on spring floods. In terms of mean annual flows, the interannual variability of the reconstructed flows were similar (except for the 1930–1940 decade), with significant changes seen in wetter and drier years. For spring floods, the interannual variabilities reconstructed were quite similar for the 1955–2011 period, but significantly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions, and finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

  • Streamflow variability over the 1881–2011 period in northern Québec: comparison of hydrological reconstructions based on tree rings and Geopotential Height field reanalysis,
    Climate of the Past, 2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Québec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

John M. Wallace - One of the best experts on this subject based on the ideXlab platform.

  • Identifying Weather Regimes in the Wintertime 500-hPa Geopotential Height Field for the Pacific–North American Sector Using a Limited-Contour Clustering Technique
    Journal of Applied Meteorology and Climatology, 2007
    Co-Authors: Joseph H Casola, John M. Wallace
    Abstract:

    Abstract A hierarchical clustering algorithm using Ward’s method has been applied to the 500-hPa Geopotential Height field in the Pacific–North American sector. In contrast to previous clustering studies that measure distance between records by using all the grid points within the domain (full-field method), the procedure outlined here, referred to as the limited-contour method, focuses on the coordinates of the 540-dam contour as the distance measure. Comparison between the regimes emerging from the two methods shows that the limited-contour method is more efficient than the full-field method with respect to grouping maps with ridges located at similar longitudes. The four regimes emerging from the limited-contour clustering analysis have been named as follows: Off-Shore Trough, Alaskan Ridge, Coastal Ridge, and Rockies Ridge. The frequencies of occurrence of the regimes have a significant relationship with the phase of the El Nino–Southern Oscillation. El Nino winters exhibit a strong preference for the...

  • identifying weather regimes in the wintertime 500 hpa Geopotential Height field for the pacific north american sector using a limited contour clustering technique
    Journal of Applied Meteorology and Climatology, 2007
    Co-Authors: Joseph H Casola, John M. Wallace
    Abstract:

    Abstract A hierarchical clustering algorithm using Ward’s method has been applied to the 500-hPa Geopotential Height field in the Pacific–North American sector. In contrast to previous clustering studies that measure distance between records by using all the grid points within the domain (full-field method), the procedure outlined here, referred to as the limited-contour method, focuses on the coordinates of the 540-dam contour as the distance measure. Comparison between the regimes emerging from the two methods shows that the limited-contour method is more efficient than the full-field method with respect to grouping maps with ridges located at similar longitudes. The four regimes emerging from the limited-contour clustering analysis have been named as follows: Off-Shore Trough, Alaskan Ridge, Coastal Ridge, and Rockies Ridge. The frequencies of occurrence of the regimes have a significant relationship with the phase of the El Nino–Southern Oscillation. El Nino winters exhibit a strong preference for the...

  • structure and seasonality of interannual and interdecadal variability of the Geopotential Height and temperature fields in the northern hemisphere troposphere
    Journal of Climate, 1993
    Co-Authors: John M. Wallace, Yuan Zhang, Kaihon Lau
    Abstract:

    Abstract Spatial patterns and seasonality of interannual and interdecadal variability in the 500-hPa Geopotential Height, sea level pressure, and 1000-500-hPa thickness field are examined based on NMC analyses over the Northern Hemisphere extratropics from 1946 onward. The leading empirical orthogonal function (EOF) of wintertime seasonal mean 500-hPa Height is closely related to the Pacific/North American (PNA) teleconnection pattern. The time series of its expansion exhibits a trend from predominantly negative values (below-normal Heights over western Canada) in the early part of the record to predominantly positive values during the 1980s. The leading EOF of sea level pressure, which is similar in summer and winter, contains elements of the North Atlantic Oscillation (NAO) and a zonally symmetric “seesaw” between polar and temperature latitudes. Its expansion coefficient exhibits relatively little memory from season to season or from year to year. The leading EOFs of summertime and annual-mean 500-hPa ...

P. Brigode - One of the best experts on this subject based on the ideXlab platform.

  • Streamflow variability over the 1881–2011 period in northern Québec: comparison of hydrological reconstructions based on tree rings and Geopotential Height field reanalysis
    Climate of the Past, 2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

  • streamflow variability over the 1881 2011 period in northern quebec comparison of hydrological reconstructions based on tree rings and Geopotential Height field reanalysis
    Climate of The Past, 2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

  • Streamflow variability over 1881–2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and on Geopotential Height field reanalysis
    2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Abstract. Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Quebec (Canada), leading to the reconstruction of flow series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir to compare the obtained streamflow series and study the natural streamflow variability over the 1881–2011 period. This new reconstruction is based, not on natural proxies, but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall-runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, both in terms of monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows, and the other one on spring floods. In terms of mean annual flows, the interannual variability of the reconstructed flows were similar (except for the 1930–1940 decade), with significant changes seen in wetter and drier years. For spring floods, the interannual variabilities reconstructed were quite similar for the 1955–2011 period, but significantly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions, and finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

  • Streamflow variability over the 1881–2011 period in northern Québec: comparison of hydrological reconstructions based on tree rings and Geopotential Height field reanalysis,
    Climate of the Past, 2016
    Co-Authors: P. Brigode, F. Brissette, A. Nicault, L. Perreault, A. Kuentz, Th. Mathevet, J. Gailhard
    Abstract:

    Over the last decades, different methods have been used by hydrologists to extend observed hydro-climatic time series, based on other data sources, such as tree rings or sedimentological datasets. For example, tree ring multi-proxies have been studied for the Caniapiscau Reservoir in northern Québec (Canada), leading to the reconstruction of flow time series for the last 150 years. In this paper, we applied a new hydro-climatic reconstruction method on the Caniapiscau Reservoir and compare the obtained streamflow time series against time series derived from dendrohydrology by other authors on the same catchment and study the natural streamflow variability over the 1881–2011 period in that region. This new reconstruction is based not on natural proxies but on a historical reanalysis of global Geopotential Height fields, and aims firstly to produce daily climatic time series, which are then used as inputs to a rainfall–runoff model in order to obtain daily streamflow time series. The performances of the hydro-climatic reconstruction were quantified over the observed period, and showed good performances, in terms of both monthly regimes and interannual variability. The streamflow reconstructions were then compared to two different reconstructions performed on the same catchment by using tree ring data series, one being focused on mean annual flows and the other on spring floods. In terms of mean annual flows, the interannual variability in the reconstructed flows was similar (except for the 1930–1940 decade), with noteworthy changes seen in wetter and drier years. For spring floods, the reconstructed interannual variabilities were quite similar for the 1955–2011 period, but strongly different between 1880 and 1940. The results emphasize the need to apply different reconstruction methods on the same catchments. Indeed, comparisons such as those above highlight potential differences between available reconstructions and, finally, allow a retrospective analysis of the proposed reconstructions of past hydro-climatological variabilities.

Ingrid Cnossen - One of the best experts on this subject based on the ideXlab platform.

  • the vertical connection of the quasi biennial oscillation modulated 11 year solar cycle signature in Geopotential Height and planetary waves during northern hemisphere early winter
    Journal of Geophysical Research, 2011
    Co-Authors: Ingrid Cnossen
    Abstract:

    [1] We analyzed observational Geopotential Height data to provide some new insights on the 11 year solar cycle signal in the Northern Hemisphere early winter and its modulation by the quasi‐biennial oscillation (QBO). The signals are strongest in the upper stratosphere. When the QBO is in its easterly phase (QBOe), it appears to move gradually eastward and poleward, resulting in a predominantly positive signal over the pole, with a weaker vertically connected negative signal over the Icelandic Low. When the QBO is in its westerly phase (QBOw), the polar stratospheric signal is mainly negative and appears connected to a negative anomaly in the troposphere over the Aleutian Low. A spectral analysis of the stratospheric response in planetary waves showed a reduction of wave number 2 power under QBOe and an enhancement of wave number 3 under QBOw. These responsesarecharacterizedbyanoverallincrease/decreaseinwaveactivityatmiddletohigh latitudes rather than a latitudinal shift of wave activity. There is no clear stratosphere‐ troposphere connection under QBOe, but under QBOw, there is a vertically coherent increase in wave power at wave numbers 1–3 with a period of 5.6–6.9 days. We suggest that the differences in response under QBOe and QBOw can be explained through differences in initial vortex strength, resulting in either a stronger influence from the low‐latitude upper stratosphere (QBOe) or from the troposphere (QBOw) on the polar stratosphere.

  • The vertical connection of the quasi‐biennial oscillation‐modulated 11 year solar cycle signature in Geopotential Height and planetary waves during Northern Hemisphere early winter
    Journal of Geophysical Research, 2011
    Co-Authors: Ingrid Cnossen
    Abstract:

    [1] We analyzed observational Geopotential Height data to provide some new insights on the 11 year solar cycle signal in the Northern Hemisphere early winter and its modulation by the quasi‐biennial oscillation (QBO). The signals are strongest in the upper stratosphere. When the QBO is in its easterly phase (QBOe), it appears to move gradually eastward and poleward, resulting in a predominantly positive signal over the pole, with a weaker vertically connected negative signal over the Icelandic Low. When the QBO is in its westerly phase (QBOw), the polar stratospheric signal is mainly negative and appears connected to a negative anomaly in the troposphere over the Aleutian Low. A spectral analysis of the stratospheric response in planetary waves showed a reduction of wave number 2 power under QBOe and an enhancement of wave number 3 under QBOw. These responsesarecharacterizedbyanoverallincrease/decreaseinwaveactivityatmiddletohigh latitudes rather than a latitudinal shift of wave activity. There is no clear stratosphere‐ troposphere connection under QBOe, but under QBOw, there is a vertically coherent increase in wave power at wave numbers 1–3 with a period of 5.6–6.9 days. We suggest that the differences in response under QBOe and QBOw can be explained through differences in initial vortex strength, resulting in either a stronger influence from the low‐latitude upper stratosphere (QBOe) or from the troposphere (QBOw) on the polar stratosphere.

Cheng Sun - One of the best experts on this subject based on the ideXlab platform.

  • space time spectral analysis of the southern hemisphere daily 500 hpa Geopotential Height
    Monthly Weather Review, 2012
    Co-Authors: Cheng Sun
    Abstract:

    In this paper the authors use the NCEP‐Department of Energy (DOE) Reanalysis 2 (NCEP2) data from 1979 to 2004 to expand the daily 500-hPa Geopotential Height in the Southern Hemisphere (SH, 908‐208S) into a double Fourier series, and analyze the temporal frequency characteristics of the expansion coefficients over various spatial scales. For the daily series over the whole year, the coefficient series of the extratropical-mean Heightischaracterizedbyasignificantlow-frequency(10‐30day)variation.Forzonalwaveswith(k,l)5(1‐5,

  • Space–Time Spectral Analysis of the Southern Hemisphere Daily 500-hPa Geopotential Height
    Monthly Weather Review, 2012
    Co-Authors: Cheng Sun
    Abstract:

    In this paper the authors use the NCEP‐Department of Energy (DOE) Reanalysis 2 (NCEP2) data from 1979 to 2004 to expand the daily 500-hPa Geopotential Height in the Southern Hemisphere (SH, 908‐208S) into a double Fourier series, and analyze the temporal frequency characteristics of the expansion coefficients over various spatial scales. For the daily series over the whole year, the coefficient series of the extratropical-mean Heightischaracterizedbyasignificantlow-frequency(10‐30day)variation.Forzonalwaveswith(k,l)5(1‐5,