Abstract
Atmospheric-oceanic circulations (teleconnections) have an important influence on regional climate. In Great Britain, the North Atlantic Oscillation (NAO) has long been understood as the leading mode of climate variability, and its phase and magnitude have been found to influence regional rainfall in previous research. The East Atlantic Pattern (EA) is also increasingly recognised as being a secondary influence on European climate. In this study we use high resolution gridded rainfall and Standardised Precipitation Index (SPI) time series data for Great Britain to map the monthly rainfall signatures of the NAO and EA over the period January 1950–December 2015. Our analyses show that the influence of the two teleconnections varies in space and time with distinctive monthly signatures observed in both average rainfall/SPI-1 values and incidences of wet/dry extremes. In the winter months the NAO has a strong influence on rainfall and extremes in the north-western regions. Meanwhile, in the southern and central regions stronger EA-rainfall relationships are present. In the summer months opposing positive/negative phases of the NAO and EA result in stronger wet/dry signatures which are more spatially consistent. Our findings suggest that both the NAO and EA have a prominent influence on regional rainfall distribution and volume in Great Britain, which in turn has implications for the use of teleconnection forecasts in water management decision making. We conclude that accounting for both NAO and EA influences will lead to an enhanced understanding of both historic and future spatial distribution of monthly precipitation.
Highlights
The North Atlantic Oscillation (NAO) has long been recognised as the first mode of climate variability in the North Atlantic region [1,2]
This study used high-resolution gridded rainfall and Standardised Precipitation Index (SPI)-1 datasets to map the monthly rainfall signatures of the North Atlantic Oscillation (NAO) and East Atlantic Pattern (EA) in Great Britain, with the aim of contributing to research exploring the interaction between these two atmospheric-oceanic circulations
Our findings show that the influence of the two teleconnections varies in space and time with distinctive signatures observed in both average rainfall/SPI-1 values and wet/dry extremes
Summary
The North Atlantic Oscillation (NAO) has long been recognised as the first mode of climate variability in the North Atlantic region [1,2]. When the SLP difference between these two meridional dipoles is greater than normal, the NAO is described as being in a positive phase (NAO+), whilst a NAO negative phase (NAO−) represents a weaker than usual difference in SLP between the Icelandic Low and Azores High [3]. North Atlantic Oscillation Indices (NAOIs) are calculated to quantify the phase and magnitude of the NAO at monthly, seasonal and annual scales, and have been used to assess the influence of the NAO on spatial distributions and deviations in rainfall, temperature and other hydrometeorological variables. During the winter in the north-west of the country positive correlations are often reported, indicating that NAO+ phases result in higher rainfall in these regions, and NAO− phases result in drier conditions [4,5,6,7,8]. In the southern and eastern regions weaker negative correlations between the NAOI and rainfall are found [8,10]
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