Signature of the North Atlantic Oscillation on British solar radiation availability and PV potential: The winter zonal seesaw

• 35% of UK interannual winter irradiance covaries with DJF Winter NAO Index (WiNAOI).
• When WiNAOI is positive (negative), irradiance anomaly is higher in East (West) UK.
• NAO is known to be scarcely predictable, but the East–West seesaw is a stable feature.
• Combining East/West power output reduces year-to-year variability of PV generation.
• Considering NAO-irradiance relation can lower uncertainty on UK energy forecasting.

The impact of the North Atlantic Oscillation (NAO) on winter solar radiation in the British Isles is explored. Records of global horizontal radiation (GHR) from a set of UK Meteorological Office pyranometers spanning the last three decades have been compared to Hurrell’s Winter NAO Index (WiNAOI). GHR in the West of Great Britain is found to be negatively correlated with WiNAOI; in eastern England, on the contrary, the correlation is significantly positive.These results disagree at least partially with the existing literature connecting NAO with irradiance in Europe, which reports a gradient of WiNAOI-versus-GHR’s correlation oriented mainly meridionally, with the correlation coefficient becoming increasingly negative with increasing latitude.The picture for Great Britain emerging from the present high resolution study, instead, shows a correlation gradient dominated by a zonal component over England; the year-to-year winter solar radiation variance associated with variations in WiNAOI is estimated to be 35% using Empirical Orthogonal Functions analysis.Over the last 16 years, monthly GHR averaged over negative WiNAOI winters is 9.3% higher in a representative South-West location with respect to positive WiNAOI years, while in a sample South-East (SE) location is 10.3% lower. This clear result could impact large photovoltaic proposals, as it links a non-negligible fraction of winter’s yield to a known climatic phenomenon. Although WiNAOI predictability is limited, the present analysis highlights that while winter solar radiation is mainly in phase with WiNAOI in the East, it is mainly in opposite phase in the West: to some extent, spatial variability can even out year-to-year variability in power yield.