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Unusual extremes in the negative phase of the Arctic Oscillation during 2009
Author(s) -
L'Heureux Michelle,
Butler Amy,
Jha Bhaskar,
Kumar Arun,
Wang Wanqiu
Publication year - 2010
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2010gl043338
Subject(s) - northern hemisphere , arctic oscillation , anomaly (physics) , stratosphere , climatology , atmospheric sciences , the arctic , environmental science , latitude , residual , arctic , southern hemisphere , oscillation (cell signaling) , geology , physics , oceanography , geodesy , chemistry , biochemistry , algorithm , computer science , condensed matter physics
During 2009, the Arctic Oscillation (AO) index was exceptionally negative during four months, which was unprecedented in a 60‐year record extending back to 1950. The negative phase of the AO corresponded to a nearly zonally symmetric anomaly of temperature and pressure over the middle‐to‐high latitudes of the Northern Hemisphere. Consistent with the strong negative phase of the AO, below‐average temperatures were also observed over North America and parts of Eurasia during June, July, October, and December 2009. Although the impact of the AO on 2‐meter temperatures was near zero when averaged over the entire hemisphere (20°–90°N), positive anomalies were evident in the residual pattern of observed temperature. The residual, along with observed below‐average stratospheric temperatures, are consistent with anthropogenic climate projections. The possible implication of the recent negative values on the long‐term AO trend is also discussed.