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Evidence for the chaotic origin of Northern Annular Mode variability
 

Summary: Evidence for the chaotic origin of Northern Annular
Mode variability
S. M. Osprey1
and M. H. P. Ambaum2
Received 18 May 2011; revised 23 June 2011; accepted 24 June 2011; published 3 August 2011.
[1] Exponential spectra are found to characterize variability
of the Northern Annular Mode (NAM) for periods less than
36 days. This corresponds to the observed rounding of the
autocorrelation function at lags of a few days. The character-
istic persistence timescales during winter and summer is
found to be 5 days for these high frequencies. Beyond per-
iods of 36 days the characteristic decorrelation timescale is
20 days during winter and 6 days in summer. We con-
clude that the NAM cannot be described by autoregressive
models for high frequencies; the spectra are more consistent
with loworder chaos. We also propose that the NAM exhibits
regime behaviour, however the nature of this has yet to be
identified. Citation: Osprey, S. M., and M. H. P. Ambaum
(2011), Evidence for the chaotic origin of Northern Annular Mode
variability, Geophys. Res. Lett., 38, L15702, doi:10.1029/

  

Source: Ambaum, Maarten - Department of Meteorology, University of Reading

 

Collections: Geosciences