title: Regional climate impacts of the Northern Hemisphere annular mode.
abstract: The Northern Hemisphere annular mode (NAM) (also known as the North Atlantic Oscillation) is shown to exert a strong influence on wintertime climate, not only over the Euro-Atlantic half of the hemisphere as documented in previous studies, but over the Pacific half as well. It affects not only the mean conditions, but also the day-to-day variability, modulating the intensity of mid-latitude storms and the frequency of occurrence of high-latitude blocking and cold air outbreaks throughout the hemisphere. The recent trend in the NAM toward its high-index polarity with stronger subpolar westerlies has tended to reduce the severity of winter weather over most middle- and high-latitude Northern Hemisphere continental regions.
authors.affiliation: Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523, USA. davet@atmos.colostate.edu
authors.forename: D W
authors.initials: DW
authors.lastname: Thompson
authors.forename: J M
authors.initials: JM
authors.lastname: Wallace