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Steven B. Feldstein and Sukyoung Lee

and DeWeaver 2007 ; Lu et al. 2008 ; Kidston et al. 2011 ). This poleward shift of the eddy-driven jet also corresponds to a trend toward the positive phase of the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) teleconnection patterns 1 ( Thompson and Wallace 2000 ). Beginning in the early 1990s, after a 20-yr upward trend toward its largest positive value, the 5-yr running mean winter NAO/AO index began to decline, becoming negative at about 2010 ( http

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Mauro Dall’Amico and Joseph Egger

in surface weather ( Thompson and Wallace 2001 ; Thompson et al. 2002 ). The dynamical coupling of the troposphere with the stratosphere 1 in the NH is captured by the northern annular mode (NAM; see Thompson and Wallace 1998 ; Baldwin and Dunkerton 1999 ; Thompson and Wallace 2000) . In the winter stratosphere the annular mode is linked to the temperature and strength of the polar vortex. In the lowermost troposphere, the NAM appears as the Arctic Oscillation and, in particular, over the

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Shangfeng Chen, Renguang Wu, Wen Chen, and Kai Li

Oscillation (NAO)/Arctic Oscillation (AO). AO is the leading mode of atmospheric interannual variability over extratropical Northern Hemisphere ( Thompson and Wallace 1998 , 2000 ). NAO is regarded as a regional manifestation of the AO over the North Atlantic region, characterizing by a meridional dipole anomaly pattern ( Hurrell and van Loon 1997 ; Thompson and Wallace 1998 ). Miyazaki and Yasunari (2008) indicated that the first EOF mode of SAT anomalies over Asia and surrounding oceans in boreal

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Judah Cohen, Jason C. Furtado, Justin Jones, Mathew Barlow, David Whittleston, and Dara Entekhabi

’s confidence in longer-term projections related to climate change. The Arctic Oscillation (AO) is the dominant mode of atmospheric winter climate variability in the extratropics ( Thompson and Wallace 1998 , 2001 ). The AO is the first empirical orthogonal function of sea level pressure (SLP) poleward of 20°N and is a measure of the meridional vacillations in the polar jet stream that consequently governs temperatures and precipitation patterns in the extratropical NH. Therefore, successfully predicting

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Shuntai Zhou and Alvin J. Miller

1. Introduction The extratropical weather and climate in the Northern Hemisphere (NH) are influenced by atmospheric circulations in both polar and tropical latitudes. The spatial and temporal variations of atmospheric circulations are often described by atmospheric modes. To the north the dominant mode is the Arctic Oscillation (AO), which has been extensively studied in recent years ( Thompson and Wallace 1998 , 2000 ; Baldwin and Dunkerton 1999 ; Hartmann et al. 2000 ). To the south the

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Y. Peings, H. Douville, J. Colin, D. Saint Martin, and Gudrun Magnusdottir

(1999) first identified a statistically significant correlation between the fall Siberian snow extent derived from satellite data and the first mode of atmospheric variability of the NH atmosphere in winter, that is, the Arctic Oscillation (AO), also referred to as the northern annular mode (NAM) (e.g., Barnston and Livezey 1987 ; Thompson and Wallace 1998 ; Kushner 2010 ). Several observational studies followed, focusing on the correlation with the North Atlantic Oscillation (NAO) (e

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Michelle L. L’Heureux and R. Wayne Higgins

: Modulation of eastern North Pacific hurricanes by the Madden–Julian oscillation. J. Climate , 13 , 1451 – 1460 . Matthews , A. J. , and M. P. Meredith , 2004 : Variability of Antarctic circumpolar transport and the Southern Annular Mode associated with the Madden–Julian Oscillation. Geophys. Res. Lett. , 31 . L24312, doi:10.1029/2004GL021666 . Miller , A. J. , S. Zhou , and S-K. Yang , 2003 : Relationship of the Arctic and Antarctic oscillations to outgoing longwave radiation. J

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Peter Hitchcock, Theodore G. Shepherd, and Gloria L. Manney

, 23 , 6438 – 6444 . Kuroda , Y. , and K. Kodera , 2001 : Variability of the polar night jet in the Northern and Southern Hemispheres . J. Geophys. Res. , 106 ( D18 ), 20 703 – 20 713 . Kuroda , Y., and K. Kodera , 2004 : Role of the Polar-night Jet Oscillation on the formation of the Arctic Oscillation in the Northern Hemisphere in winter. J. Geophys. Res., 109, D11112, doi:10.1029/2003JD004123 . Liberato , M. L. R. , J. M. Castanheira , L. de la Torre , C. C

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Yueqing Li and Song Yang

-scale atmospheric and oceanic processes. For example, the Arctic Oscillation (AO) influences not only the climate over the north polar region and the North Atlantic but also the Siberian high (SH) and EAWM ( Thompson and Wallace 1998 ; Wu and Wang 2002 ). Li (1989) showed that weak (strong) EAWM usually occurs following the mature phase of El Niño (La Niña). Anomalous anticyclonic (cyclonic) circulation usually exists over the Philippine Sea during El Niño (La Niña) winters ( Wang et al. 2000 ), and thus

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Shih-Yu Wang, Jin-Ho Yoon, Robert R. Gillies, and Changrae Cho

disturbances) through Nepal. Pronounced interannual variability of winter storm occurrences is correlated with the polar/Eurasia teleconnection pattern ( Lang and Barros 2004 ; Li et al. 2008 ), which links other larger-scale natural climate variabilities, such as the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO), to the winter climate of Nepal. In western Nepal, winter monthly precipitation amounts are on the order of 50 mm or less. The region is particularly reliant on this

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