North Atlantic Oscillation amplifies orographic precipitation and river flow in upland Britain

Burt, T. P.; Howden, Nicholas J K

doi:10.1002/wrcr.20297

Cited by 67 publications

(96 citation statements)

References 46 publications

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“…For example, for the winter season (Fig. 5b) the decadal pattern of the rainfall medians agrees with that of the North Atlantic Oscillation Index, which is known to have an influence on winter precipitations in the UK (Burt and Howden, 2013). The difference between the decadal patterns for rainfall (Fig.…”

Section: Gridded Daily Rainfall Datasupporting

confidence: 69%

Non-stationarity in annual and seasonal series of peak flow and precipitation in the UK

Prosdocimi

Kjeldsen

Svensson

2014

Nat. Hazards Earth Syst. Sci.

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Abstract. When designing or maintaining an hydraulic structure, an estimate of the frequency and magnitude of extreme events is required. The most common methods to obtain such estimates rely on the assumption of stationarity, i.e. the assumption that the stochastic process under study is not changing. The public perception and worry of a changing climate have led to a wide debate on the validity of this assumption. In this work trends for annual and seasonal maxima in peak river flow and catchment-average daily rainfall are explored. Assuming a two-parameter log-normal distribution, a linear regression model is applied, allowing the mean of the distribution to vary with time. For the river flow data, the linear model is extended to include an additional variable, the 99th percentile of the daily rainfall for a year. From the fitted models, dimensionless magnification factors are estimated and plotted on a map, shedding light on whether or not geographical coherence can be found in the significant changes. The implications of the identified trends from a decisionmaking perspective are then discussed, in particular with regard to the Type I and Type II error probabilities. One striking feature of the estimated trends is that the high variability found in the data leads to very inconclusive test results. Indeed, for most stations it is impossible to make a statement regarding whether or not the current design standards for the 2085 horizon can be considered precautionary. The power of tests on trends is further discussed in the light of statistical power analysis and sample size calculations. Given the observed variability in the data, sample sizes of some hundreds of years would be needed to confirm or negate the current safety margins when using at-site analysis.

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Section: Gridded Daily Rainfall Datasupporting

confidence: 69%

Non-stationarity in annual and seasonal series of peak flow and precipitation in the UK

Prosdocimi

Kjeldsen

Svensson

2014

Nat. Hazards Earth Syst. Sci.

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“…Recent studies have found strong relationships between the NAO and winter and annual runoff (e.g. Burt and Howden, 2013;Laizé and Hannah, 2010) and high flows (Biggs and Atkinson, 2011; Hannaford and Marsh, 2008) in northern and western areas. This body of research suggests the wetter winters -and associated river flow patterns -observed in upland areas are influenced by changes in westerly airflows linked to multi-decadal variability in the NAO.…”

Section: Low Flows and Hydrological Drought Indicatorsmentioning

confidence: 99%

Climate-driven changes in UK river flows

Hannaford¹

2015

Progress in Physical Geography: Earth and Environment

107

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There is a burgeoning international literature on hydro-climatic trend detection, motivated by the need to detect and interpret any emerging changes in river flows associated with anthropogenic climate change. The UK has a particularly strong evidence base in this area thanks to a well-developed monitoring programme and a wealth of studies published over the last 20 years. This paper reviews this research, with a view to assessing the evidence for climate change influences on UK river flow, including floods and droughts. This assessment is of international relevance given the scale of the research effort in the UK, a densely monitored and data-rich environment, but one with significant human disturbances to river flow regimes, as in many parts of the world. The review finds that changes can be detected in river flow regimes, some of which agree with future change projections, while others are in apparent contradiction. Observed changes generally cannot be attributed to climate change, largely due to the fact that river flow records are limited in length and the identification of short-term trends is confounded by natural variability. A UK 'Benchmark' network of nearnatural catchments is an internationally significant example of an initiative to enable climate variability to be discerned from direct human disturbances (e.g. abstractions, dam construction). Generally, however, the problem of attribution has been tackled rather indirectly in the UK, as elsewhere, and more efforts are required to attribute change in a more rigorous manner.

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“…The NAO is the dominant mode of natural climate variability in the region (Hurrell and Van Loon, 1997;Wilby et al, 1997), with positive phases of the NAO index associated with increased westerly airflow and positioning of storm tracks over north-western Europe. The NAO influence in winter has subsequently been linked to extreme rainfalls (Maraun et al, 2011), winter runoff (Laizé and Hannah, 2010), high flows (Hannaford and Marsh, 2008) and enhanced orographic rainfall (Burt and Howden, 2013) in the British Isles. Similarly, Leahy and Kiely (2011) report an increase in March and October hourly rainfall in 1975 across Ireland, with a corresponding decrease in July rainfall.…”

Section: Evidence Of Widespread Installation Ofmentioning

confidence: 99%

Attribution of detected changes in streamflow using multiple working hypotheses

Harrigan

Murphy

Hall

et al. 2014

Hydrol. Earth Syst. Sci.

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Abstract. This paper revisits a widely cited study of the Boyne catchment in east Ireland that attributed greater streamflow from the mid-1970s to increased precipitation linked to a shift in the North Atlantic Oscillation. Using the method of multiple working hypotheses we explore a wider set of potential drivers of hydrological change. Rainfallrunoff models are used to reconstruct streamflow to isolate the effect of climate, taking account of both model structure and parameter uncertainty. The Mann-Kendall test for monotonic trend and Pettitt change point test are applied to explore signatures of change. Contrary to earlier work, arterial drainage and simultaneous onset of field drainage in the 1970s and early 1980s are now invoked as the predominant drivers of change in annual mean and high flows within the Boyne. However, a change in precipitation regime is also present in March, thereby amplifying the effect of drainage. This new explanation posits that multiple drivers acting simultaneously were responsible for the observed change, with the relative contribution of each driver dependant on the timescale investigated. This work demonstrates that valuable insights can be gained from a systematic application of the method of multiple working hypotheses in an effort to move towards more rigorous attribution, which is an important part of managing emerging impacts on hydrological systems.

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North Atlantic Oscillation amplifies orographic precipitation and river flow in upland Britain

Cited by 67 publications

References 46 publications

Non-stationarity in annual and seasonal series of peak flow and precipitation in the UK

Non-stationarity in annual and seasonal series of peak flow and precipitation in the UK

Climate-driven changes in UK river flows

Attribution of detected changes in streamflow using multiple working hypotheses

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