Relationship between NAO and wind climate over Norway

Abstract

This study investigates the strength of the relationship between the large-scale atmospheric phenomenon known as the North Atlantic Oscillation (NAO) and the Norwegian winter wind climate. The relationship is measured through spatial and temporal correlations of wind climate measures derived from reanalysis datasets and the winter NAO index for the time period 1920 to 2010. Wind speeds exceeding specific thresholds, percentile wind speeds, and wind direction frequencies are correlated with the NAO index. The results show strong and significant correlations for median and strong wind speeds over southern Norway and along the western coast to about 68° N. The results also indicate that a positive NAO is strongly associated with increased frequencies of winds from the southwest and decreased frequencies of winds from the northeast. There is no significant relationship between wind climate and the NAO for the northernmost part of the country. Time series reflect a temporal variability in the strength of the relationship with the NAO, where a stronger relationship is found during time periods containing the most extreme NAO phases. Due to the lack of correlations in northern Norway, a correlation analysis with the Barents Oscillation, which is a dominating mode of variability over the Barents region, was also conducted, but yielded no strong and significant correlation at any point across Norway. The implications of the variation in correlations, particularly those associated with geo - graphy and choice of wind climate metric for wind energy production, are discussed.