Premium
Does the North Atlantic Oscillation show unusual persistence on intraseasonal timescales?
Author(s) -
Keeley S. P. E.,
Sutton R. T.,
Shaffrey L. C.
Publication year - 2009
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 - 10.1029/2009gl040367
Subject(s) - climatology , north atlantic oscillation , autocorrelation , environmental science , persistence (discontinuity) , madden–julian oscillation , teleconnection , empirical orthogonal functions , el niño southern oscillation , oscillation (cell signaling) , atmospheric sciences , geology , meteorology , geography , mathematics , statistics , biology , convection , geotechnical engineering , genetics
Previous studies have argued that the autocorrelation of the winter North Atlantic Oscillation (NAO) index provides evidence of unusually persistent intraseasonal dynamics. We demonstrate that the autocorrelation on intraseasonal time‐scales of 10–30 days is sensitive to the presence of interannual variability, part of which arises from the sampling of intraseasonal variability and the remainder of which we consider to be “externally forced”. Modelling the intraseasonal variability of the NAO as a red noise process we estimate, for winter, ∼70% of the interannual variability is externally forced, whereas for summer sampling accounts for almost all of the interannual variability. Correcting for the externally forced interannual variability has a major impact on the autocorrelation function for winter. When externally forced interannual variability is taken into account the intrinsic persistence of the NAO is very similar in summer and winter (∼5 days). This finding has implications for understanding the dynamics of the NAO.