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| Titel |
Extreme fluctuations of vertical velocity in the unstable atmospheric surface layer |
| VerfasserIn |
L. Liu, F. Hu, X.-L. Cheng |
| 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 ; 21, no. 2 ; Nr. 21, no. 2 (2014-04-04), S.463-475 |
| Datensatznummer |
250120906
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| Publikation (Nr.) |
 copernicus.org/npg-21-463-2014.pdf |
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| Zusammenfassung |
| In this paper, we propose a new method to extract the extreme fluctuations of
vertical velocity in the unstable atmospheric surface layer. Unlike the
commonly used conditional sampling analysis, this method defines a threshold
by using a systematical method and tries to reduce the artificiality in this
process. It defines threshold as the position where the types of probability
density functions (PDFs) of vertical velocity fluctuations begin to change
character from stable distributions to truncated stable distributions.
Absolute values of fluctuations greater than the threshold are considered to
be extreme fluctuations. We then analyze the statistical characteristics of
extracted extreme fluctuations of vertical velocity. Our results show that
the amplitudes of extreme fluctuations are exponentially distributed, and the
waiting times between extreme fluctuations have stretched exponential
distributions. It suggests that there are statistical correlations in the
time series of vertical velocity because independent time series can only
have exponentially distributed waiting times. The durations of extreme
fluctuations are also found to be stretched exponential distributed, while
for the independent time series the distributions of durations are
delta-like. Finally, the PDFs of amplitudes, waiting times and durations are
all well parameterized in the context of Monin–Obukhov theory. |
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