Spatio-Temporal Variability in North Atlantic Oscillation Monthly Rainfall Signatures in Great Britain

Abstract

The North Atlantic Oscillation (NAO) is the primary atmospheric-oceanic circulation/teleconnection influencing regional climate in Great Britain. As our ability to predict the NAO several months in advance increases, it is important that we improve our spatio-temporal understanding of the rainfall signatures that the circulation produces. We undertake a high resolution spatio-temporal analysis quantifying variability in rainfall response to the NAO across Great Britain. We analyse and map monthly NAO-rainfall response variability, revealing the spatial influence of the NAO on rainfall distributions, and particularly the probability of wet and dry conditions/extremes. During the winter months, we identify spatial differences in the rainfall response to the NAO between the NW and SE areas of Britain. The NW area shows a strong and more consistent NAO-rainfall response, with greater probability of more extreme wet/dry conditions. However, greater NAO-rainfall variability during winter was found in the SE. The summer months are marked by a more spatially consistent rainfall response; however, we find that there is variability in both wet/dry magnitude and directionality. We note the implications of these spatially and temporally variable NAO-rainfall responses for regional hydrometeorological predictions and highlight the potential explanatory role of other atmospheric-oceanic circulations.

Monthly Rainfall Signatures of the North Atlantic Oscillation and East Atlantic Pattern in Great Britain

“…However, West et al [21] observe that whilst average and relatively consistent rainfall responses to the NAO across Great Britain can be observed in line with the above descriptions, there can also be significant spatio-temporal variability in regional NAO-rainfall responses. For example, whilst in the north-west of the country more consistent NAO+/− wet/dry rainfall responses in winter were found, significant NAO-rainfall variability can occur in the central, southern and eastern areas, with some regions having equal likelihood of wetter/drier conditions and extremes [21]. The spatial and temporal variability in the rainfall response to the NAO across Great Britain has been noted as a potentially limiting factor in the inclusion of even highly accurate monthly/seasonal NAO forecasts in water management decision making [13,21,22].…”

“…Significant positive correlations between the EA and rainfall have been reported across Great Britain [23,30] with precipitation anomalies in the central, southern and eastern regions possibly associated with varying phases of the EA [13]. Interestingly, these are the same regions West et al [21] note as having greater variability in NAO-rainfall response. In the summer months positive EA-rainfall correlations persist, albethey of a weaker strength [13].…”

“…For example, whilst in the north-west of the country more consistent NAO+/− wet/dry rainfall responses in winter were found, significant NAO-rainfall variability can occur in the central, southern and eastern areas, with some regions having equal likelihood of wetter/drier conditions and extremes [21]. The spatial and temporal variability in the rainfall response to the NAO across Great Britain has been noted as a potentially limiting factor in the inclusion of even highly accurate monthly/seasonal NAO forecasts in water management decision making [13,21,22].…”

“…NAO-rainfall response variability may be associated with the phase and magnitude of other North Atlantic/European atmospheric-oceanic circulations which may enhance or moderate the effect of the NAO in influencing regional rainfall in Great Britain [13,21]. Research continues to highlight the importance of the East Atlantic Pattern (EA) in influencing European climate.…”

“…Given the variability that can be observed in NAO rainfall signatures [21,22], interactions between the NAO and EA and their combined effect on spatial rainfall distributions across the North Atlantic and Europe have been explored. Moore et al [31,32] found that the EA has the potential to influence the location and magnitude of the NAO dipoles.…”