An Extended Pacific–North American Index from Upper-Air Historical Data Back to 1922

Ewen, Tracy; Brönnimann, Stefan; Annis, Jeffrey L.

doi:10.1175/2007jcli1951.1

Cited by 24 publications

(20 citation statements)

References 46 publications

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“…S4). The GLS trend analysis of instrumental data confirms that the PDO and the PNA, with their similar low-frequency components (28), have a significant impact on historical ARB flows (8). In the 900-y proxy flow record, the MCA spectrum contains the modes of variability typical of the PDO and the associated North Pacific Index.…”

Section: Discussionmentioning

confidence: 68%

Long-term reliability of the Athabasca River (Alberta, Canada) as the water source for oil sands mining

Sauchyn

St‐Jacques

Luckman

2015

Proc. Natl. Acad. Sci. U.S.A.

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Exploitation of the Alberta oil sands, the world's third-largest crude oil reserve, requires fresh water from the Athabasca River, an allocation of 4.4% of the mean annual flow. This allocation takes into account seasonal fluctuations but not long-term climatic variability and change. This paper examines the decadal-scale variability in river discharge in the Athabasca River Basin (ARB) with (i) a generalized least-squares (GLS) regression analysis of the trend and variability in gauged flow and (ii) a 900-y tree-ring reconstruction of the water-year flow of the Athabasca River at Athabasca, Alberta. The GLS analysis removes confounding transient trends related to the Pacific Decadal Oscillation (PDO) and Pacific North American mode (PNA). It shows long-term declining flows throughout the ARB. The tree-ring record reveals a larger range of flows and severity of hydrologic deficits than those captured by the instrumental records that are the basis for surface water allocation. It includes periods of sustained low flow of multiple decades in duration, suggesting the influence of the PDO and PNA teleconnections. These results together demonstrate that low-frequency variability must be considered in ARB water allocation, which has not been the case. We show that the current and projected surface water allocations from the Athabasca River for the exploitation of the Alberta oil sands are based on an untenable assumption of the representativeness of the short instrumental record.paleohydrology | statistical hydrology | oil sands | Alberta | climate variability

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Section: Discussionmentioning

confidence: 68%

Long-term reliability of the Athabasca River (Alberta, Canada) as the water source for oil sands mining

Sauchyn

St‐Jacques

Luckman

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Similar to the approach used in several recent studies (Ewen et al, 2008;Finger et al, 2015;Fitzner et al, 2013;Haberlandt and Sester, 2010;Seibert and Beven, 2009), we pretended that only a small subset of the data were available. In addition, various degrees of inaccuracy were assumed.…”

Section: Methodsmentioning

confidence: 99%

Value of uncertain streamflow observations for hydrological modelling

Etter¹,

Strobl²,

Seibert³

et al. 2018

Preprint

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Abstract.Previous studies have shown that a hydrological model can be parameterized using on a limited number of streamflow measurements for otherwise ungauged basins. Citizen science projects can collect such data but an important question is whether these observations are informative given that these streamflow estimates will be uncertain. We address the value of inaccurate streamflow estimates for calibration of a simple bucket-type runoff model for six Swiss catchments. We 10 pretended that only a few observations were available and that these were affected by different levels of inaccuracy. The initial inaccuracy level was based on a log-normal error distribution that was fitted to streamflow estimates of 136 citizens for medium-sized streams. Two additional levels of inaccuracy, for which the standard deviation of the error-distribution was divided by two and four, were used as well. Based on these error distributions, random errors were added to the measured hourly streamflow data. New time series with different temporal resolutions were created from these synthetic time series. 15These included scenarios with one observation each week or month and scenarios that are more realistic for crowdsourced datasets with irregular distributions throughout the year or a focus on spring or summer. The model was then calibrated for the six catchments using the synthetic time series for a dry, an average and a wet year. The performance of the calibrated models was evaluated based on the measured hourly streamflow time series. The results indicate that streamflow estimates from untrained citizens are not informative for model calibration. However, if the errors can be reduced, the estimates are 20 informative and useful for model parameterization. As expected, the model performance increased when the number of observations used for calibration increased. The model performance was also better when the observations were more evenly distributed throughout the year. This study indicates that uncertain streamflow estimates can be useful for model calibration but that the estimates by citizen scientists need to be improved by training or more advanced data filtering before they are useful for model calibration. 25 IntroductionThe application of hydrological models usually requires several years of precipitation, temperature and streamflow data for calibration, but these data are only available for a limited number of catchments. Therefore, several studies have addressed the question how much data are needed to calibrate a model for a catchment where continuous streamflow data are not available.Hydrol. Earth Syst. Sci. Discuss., https://doi

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“…The interannual variability is dominated by ENSO and the zonal mean tropical and subtropical circulation (correlations with HC and SJ are strong). On the decadal scale a relation to the Pacific Decadal Oscillation (PDO) is found (see EWEN et al, 2008b). Note that in the combined (reconstructed and reanalysis-based) series, we also found a statistically significant, though weak, relation to the NAO (see EWEN et al, 2008b).…”

Section: H) the Pacific North American Patternmentioning

confidence: 78%

“…2 in the form of seasonal mean values of the reduction of error (RE, see COOK et al, 1994). Values of RE can lie between −∞ and 1, where RE > 0 is normally considered an indication that the model has skill (RE values for DIMI and PNA are from EWEN et al, 2008b andZHOU et al, 2009a and are of the VAL1 type).…”

Section: Eschweizerbartxxx Authormentioning

confidence: 99%

Variability of large-scale atmospheric circulation indices for the northern hemisphere during the past 100 years

Brönnimann¹,

Stickler²,

Griesser

et al. 2009

metz

Self Cite

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We present an analysis of the large-scale atmospheric circulation variability since 1900 based on various circulation indices. They represent the main features of the zonal mean circulation in the northern hemisphere in boreal winter (such as the Hadley circulation, the subtropical jet, and the polar vortex in the lower stratosphere) as well as aspects of the regional and large-scale circulation (the Pacific Walker Circulation, the Indian monsoon, the North Atlantic Oscillation, NAO, and the Pacific North American pattern, PNA). For the past decades we calculate the indices from different reanalyses (NCEP/NCAR, ERA-40, JRA-25, ERAInterim). For the first half of the 20 th century the indices are statistically reconstructed based on historical upper-air and surface data as well as calculated from the Twentieth Century Reanalysis. The indices from all these observation-based data sets are compared to indices calculated from a 9-member ensemble of "all forcings" simulations performed with the chemistry-climate model SOCOL. After discussing the agreement among different data products, we analyse the interannual-to-decadal variability of the indices in the context of possible driving factors, such as El Niño/Southern Oscillation (ENSO), volcanic eruptions, and solar activity. The interannual variability of the Hadley cell strength, the subtropical jet strength, or the PNA is well reproduced by the model ensemble mean, i.e., it is predictable in the context of the specified forcings. The source of this predictability is mainly related to ENSO (or more generally, tropical sea-surface temperatures). For other indices such as the strength of the stratospheric polar vortex, the NAO, or the poleward extent of the Hadley cell the correlations between observations and model ensemble mean are much lower, but so are the correlations within the model ensemble. Multidecadal variability and trends in the individual series are discussed in the context of the underlying anthropogenic and natural forcings. While consistent trends were found for some of the indices, results also indicate that care should be taken when analysing trends in reconstructions or reanalysis data. ZusammenfassungDiese Studie präsentiert Ergebnisse einer Analyse der Variabilität der großräumigen, atmosphärischen Zirkulation seit 1900, basierend auf verschiedenen Zirkulationsindizes. Die Indizes umfassen sowohl die Hauptcharakteristika der zonal gemittelten, nordhemisphärischen Zirkulation im Nordwinter (z.B. HadleyZirkulation, Subtropenjet und polarer Vortex in der unteren Stratosphäre) als auch Aspekte der regionalen und großräumigen Zirkulation (pazifische Walker-Zirkulation, indischer Monsun, nordatlantische Oszillation (NAO) und das "Pacific North American"-Muster (PNA)). Die Indizes wurden für die letzten Dekaden aus verschiedenen Reanalysen berechnet (NCEP/NCAR, ERA-40, JRA-25, ERA-Interim). Für die erste Hälfte des 20. Jahrhunderts wurden sie dagegen, basierend auf historischen Bodendaten und Messdaten aus der freien Troposphäre, statistisch rek...

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An Extended Pacific–North American Index from Upper-Air Historical Data Back to 1922

Cited by 24 publications

References 46 publications

Long-term reliability of the Athabasca River (Alberta, Canada) as the water source for oil sands mining

Long-term reliability of the Athabasca River (Alberta, Canada) as the water source for oil sands mining

Value of uncertain streamflow observations for hydrological modelling

Variability of large-scale atmospheric circulation indices for the northern hemisphere during the past 100 years

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