The Recent Trend and Variance Increase of the Annular Mode

This study examines whether both the trend and the increase in variance of the Northern Hemisphere winter annular mode during the past 30 years arise from atmospheric internal variability. To address this question, a synthetic time series is generated that has the same intraseasonal stochastic prope...

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Bibliographic Details
Published in:Journal of climate 2002-01, Vol.15 (1), p.88-94
Main Author: Feldstein, Steven B.
Format: Article
Language:English
Subjects:
Atmosphere
Atmospherics
Climate
Climate change
Climate models
Climatology. Bioclimatology. Climate change
Earth cryosphere
Earth, ocean, space
Exact sciences and technology
External geophysics
Meteorology
Noise spectra
Seasons
Spectral index
Statistical mode
Statistical variance
Time series
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Summary:This study examines whether both the trend and the increase in variance of the Northern Hemisphere winter annular mode during the past 30 years arise from atmospheric internal variability. To address this question, a synthetic time series is generated that has the same intraseasonal stochastic properties as the annular mode. By generating a distribution of linear trend values for the synthetic time series, and through a chi-square statistical analysis, it is shown that this trend and variance increase are well in excess of the level expected from internal variability of the atmosphere. This implies that both the trend and the variance increase of the annular mode are due either to coupling with the hydrosphere and/or cryosphere or to driving external to the climate system. This behavior contrasts that of the first 60 years of the twentieth century, for which it is shown that all of the interannual variability of the annular mode can be explained by atmospheric internal variability.
ISSN:0894-8755
1520-0442
DOI:10.1175/1520-0442(2002)015<0088:trtavi>2.0.co;2