Report

Regional Climate Impacts of the Northern Hemisphere Annular Mode

Science  06 Jul 2001:
Vol. 293, Issue 5527, pp. 85-89
DOI: 10.1126/science.1058958

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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.

  • * To whom correspondence should be addressed. E-mail: davet{at}atmos.colostate.edu

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