The Influence of the North Atlantic–Arctic Oscillation on Mean, Variance, and Extremes of Temperature in the Northeastern United States and Canada

An analysis of detailed relationships between the North Atlantic Oscillation–Arctic Oscillation (NAO–AO) and local temperature response throughout the northeastern United States and neighboring areas of Canada is presented. In particular, the study focuses on how contrasts in the mean and daily variance, based on AO phase, are associated with contrasts in the frequency and intensity of extreme temperature events in both winter and spring. In this region, notable contrasts in mean temperatures in winter and daily variance in spring, which influence the pattern of extremes, are associated with phases of the NAO–AO. Warmer temperatures in New England and cooler temperatures in Quebec, Canada, result during winter with increases in the NAO–AO index. The mean temperature response is weaker in spring, but the response of daily variance of temperature is stronger; variance increases with the NAO–AO index. Relationships between these effects help explain significant increases in maximum temperature extremes during winter in New England and in minimum temperature extremes during spring in Quebec for high NAO–AO index years. Diurnal temperature range tends to be larger in AO-positive winters and springs throughout the region. This study helps put other work on the trends in regional extreme events into the context of large-scale climate variability.