Preprints
https://doi.org/10.5194/hess-2021-572
https://doi.org/10.5194/hess-2021-572

  12 Nov 2021

12 Nov 2021

Review status: this preprint is currently under review for the journal HESS.

The importance of non-stationary multiannual periodicities in the NAO index for forecasting water resource extremes

William Rust1, John Bloomfield2, Mark Cuthbert3,4, Ron Corstanje5, and Ian Holman1 William Rust et al.
  • 1Cranfield Water Science Institute (CWSI), Cranfield University, Bedford MK43 0AL
  • 2British Geological Survey, Wallingford, OX10 8BB
  • 3School of Earth and Environmental Sciences, Cardiff University, Park Place, Cardiff, CF10 3AT
  • 4School of Civil and Environmental Engineering, The University of New South Wales, Sydney, Australia
  • 5Centre for Environment and Agricultural Informatics, Cranfield University, Bedford MK43 0AL

Abstract. Drought forecasting and early warning systems for water resource extremes are increasingly important tools in water resource management, particularly in Europe where increased population density and climate change are expected to place greater pressures on water supply. In this context, the North Atlantic Oscillation (NAO) ais often used to indicate future water resource behaviours (including droughts) over Europe, given its dominant control on winter rainfall totals in the North Atlantic region. Recent hydroclimate research has focused on the role of multiannual periodicities in the NAO in driving low frequency behaviours in some water resources, suggesting that notable improvements to lead-times in forecasting may be possible by incorporating these multiannual relationships. However, the importance of multiannual NAO periodicities for driving water resource behaviour, and the feasibility of this relationship for indicating future droughts, has yet to be assessed in the context of known non-stationarities that are internal to the NAO and its influence on European meteorological processes. Here we quantify the time-frequency relationship between the NAO and a large dataset of water resources records to identify key non-stationarities that have dominated multiannual behaviour of water resource extremes over recent decades. The most dominant of these is a 7.5-year periodicity in water resource extremes since approximately 1970 but which has been diminishing since 2005. Furthermore, we show that the non-stationary relationship between the NAO and European rainfall is clearly expressed at multiannual periodicities in the water resource records assessed. These multiannual behaviours are found to have modulated historical water resource anomalies to an extent that is comparable to the projected effects of a worst-case climate change scenario. Furthermore, there is limited systematic understanding in existing atmospheric research for non-stationaries in these periodic behaviours which poses considerable implications to existing water resource forecasting and projection systems, as well as the use of these periodic behaviours as an indicator of future water resource drought.

William Rust et al.

Status: open (until 07 Jan 2022)

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William Rust et al.

William Rust et al.

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Short summary
We highlight the importance of the North Atlantic Oscillation in controlling droughts in the UK. Specifically, multi-year cycles in the NAO are shown to influence the frequency of Droughts and that this influence changes considerably over time. We show that the influence of these varying controls is similar to the projected effects of climate change on water resources. We show that these time-varying behaviours have important implications for water resource forecasts used for drought planning.