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| Titel |
Quantification of Europe-wide streamflow complexity and potential links to atmospheric circulation patterns |
| VerfasserIn |
L. Gudmundsson, H. Lange, L. M. Tallaksen, K. Stahl |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024634
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| Zusammenfassung |
| Stream flow observations from a geographical region are known to often exhibit strong
common behavior. In order to assess the temporal evolution of the complexity of stream
flow time series from all over Europe, we employ the recently developed Linear
Variance Decay dimension density (δLV D). It is estimated as the parameter of an
exponential decay function fitted to the remaining variances of the eigenvalues of
a covariance matrix. Scaling between zero and one, δLV D can be interpreted as
a measure of the proportion of linear independent components in a multivariate
record.
We analyze a large set (400) of daily European streamflow series taken from the European
Water Archive (EWA), covering the period 1963 to 2005. We compute δLV D series for
monthly aggregations as well as for a one-year long moving window (at monthly time steps).
The resulting two series are highly structured. The series representing monthly δLV D values
has a distinct annual cycle with the least complexity in the winter months. The series with the
running annual δLV D values has a significant downward trend that accounts for 37% of the
variance. In order to detect oscillatory behavior, we use Monte Carlo Singular System
Analysis. We detect two significant oscillatory modes with large spectral power on narrow
periodic bands (2.2 - 3.4 and 1.9 -2.9 years). These modes together account for 15% of the
variance.
In order to seek the origin of these periodicities, we compare them to periodic
components of northern hemisphere teleconnection indices. Among a variety of
indices explored, the East Atlantic Pattern (EA), the West Pacific Pattern (WP)
and the East Atlantic/West Russia Pattern (EA/WR) have modes with significant
variability in the 1.9 to 2.9 years band. However only the signal extracted from
EA/WR is strongly related to periodic behavior in the δLV D series of European stream
flow.
Thus we conclude that an two to three year oscillation in the EA/WR may drive weather
patterns that influence the strength of synchronous behavior of pan European stream
flow. |
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