North Atlantic centers of action and seasonal to subseasonal temperature variability in Europe and eastern North America

Abstract

AbstractThe North Atlantic Oscillation (NAO) is one of the most prominent patterns of atmospheric circulation variability in the Northern Hemisphere. Its climate impacts have been identified for regions extending from North America to northern Asia and the Middle East, with implications for sub‐seasonal variability and, in some cases, meteorological trends over multiple years to decades. The NAO itself, however, is the combined expression of two pressure centers: the Icelandic Low and the Azores High. Previous work has shown that when these “centers of action” (CoA) are separated out and studied they can often provide better insight and explanatory power than the NAO does on its own. Here, we analyse the influence that the CoA have on daily minimum air temperature in winter and daily maximum temperature in summer in eastern North America and Europe. The paper has two goals: (a) to characterize CoA associations with temperature on a range of timescales, including sub‐seasonal analyses that reflect short‐term dynamics of the CoA and that are frequently ignored in NAO teleconnection studies, and (b) to evaluate NAO and CoA influence on temperature across seasons (winter and summer) and in upstream and downstream regions (eastern North America and Europe) using a consistent combination of datasets and methods, in order to contextualize results from prior studies that targeted a single region or season. We find that associations with summertime daily maximum and wintertime daily minimum temperatures are strongest for seasonal averages, but select CoA indices inform explanation of temperature variability at subseasonal timescales. The strength of the Icelandic Low and the location of both CoA show strong associations in winter, while in summer the locations of the CoA show temperature associations that are distinct from and sometimes stronger than those found for CoA strength or NAO indices.