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| Titel |
Error growth and dynamical vectors during southern hemisphere blocking |
| VerfasserIn |
M. Wei, J. S. Frederiksen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 11, no. 1 ; Nr. 11, no. 1 (2004-02-25), S.99-118 |
| Datensatznummer |
250009027
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| Publikation (Nr.) |
 copernicus.org/npg-11-99-2004.pdf |
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| Zusammenfassung |
| The structural organization of initially random perturbations or "errors"
evolving in a barotropic tangent linear model with time-dependent basic
states taken from observations, is examined for cases of block development,
maturation and decay in the Southern Hemisphere atmosphere during April,
November and December 1989. We determine statistical results relating
the structures of evolved errors to singular vectors (SVs), Lyapunov
vectors (LVs) and finite-time normal modes (FTNMs). The statistics of
100 evolved error fields are studied for six day periods or longer and
compared with the growth and structures of leading fast growing SVs, LVs
and FTNMs. The SVs are studied in the kinetic energy (KE), enstrophy (EN)
and streamfunction (SF) norms, while all FTNMs and the first LV are norm
independent. The mean of the largest pattern correlations between the
100 error fields and dynamical vectors, taken over the five fastest growing
SVs, in any of the three norms, or over the five fastest growing FTNMs,
increases with increasing time interval to a value close to 0.6 after six
days. Corresponding pattern correlations with the five fastest growing LVs
are slightly lower. The leading dynamical vectors (SVs 1, FTNM1 or LV 1)
generally, but not always, give the largest pattern correlations with the
error fields. It is found that viscosity slightly increases the average
correlations between the evolved errors and LV 1 and evolved SVs 1. Mean
pattern correlations with fast growing dynamical vectors increase further
for time intervals longer than six days. The properties of the dynamical vectors during Southern Hemisphere blocking
are briefly outlined. After a few days integration, the structures of
the leading evolved SVs in the KE, EN and SF norms, are in general quite
similar and also similar to some of the dominant FTNMs that are norm
independent. For optimization times of six days or less, the evolved
SVs and FTNMs are, in general, different from the dominant LVs on the same
day. Nevertheless, amplification factors of the first FTNMs and first
LVs are very similar, and also similar to, but slightly larger than,
the mean amplification factor of 100 initially random perturbations in
the SF norm, while the amplification factors in the SF norm of KE SVs 1
and SF SV 1 are much higher. For longer optimization times, the first
SVs and the first FTNM increasingly turn towards the leading LV with
convergence achieved within a month. |
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