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| Titel |
Non-stationarity in daily and sub-daily intense rainfall – Part 1: Sydney, Australia |
| VerfasserIn |
D. Jakob, D. J. Karoly, A. Seed |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 11, no. 8 ; Nr. 11, no. 8 (2011-08-19), S.2263-2271 |
| Datensatznummer |
250009625
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| Publikation (Nr.) |
 copernicus.org/nhess-11-2263-2011.pdf |
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| Zusammenfassung |
This study was driven by a need to clarify how variations in climate might
affect intense rainfall and the potential for flooding. Sub-daily durations
are of particular interest for urban applications. Worldwide, few such
observation-based studies exist, which is mainly due to limitations in data.
While there are still large discrepancies between precipitation data sets
from observations and models, both show that there is a tendency for moist
regions to become wetter and for dry regions to become drier. However,
changes in extreme conditions may show the opposite sign to those in average
conditions. Where changes in observed intense precipitation have been
studied, this has typically been for daily durations or longer.
The purpose of this two-part study is to examine daily and sub-daily
rainfall extremes for evidence of non-stationarity. Here the problem was
addressed by supplementing one long record (Part 1) by a set of shorter
records for a 30-yr concurrent period (Part 2). Variations in frequency
and magnitude of rainfall extremes across durations from 6 min to 72 h
were assessed using data from sites in the south-east of Australia. For the
analyses presented in this paper, a peaks-over-threshold approach was chosen
since it allows investigating changes in frequency as well as magnitude.
Non-parametric approaches were used to assess changes in frequency,
magnitude, and quantile estimates as well as the statistical significance of
changes for one station (Sydney Observatory Hill) for the period 1921 to
2005. Deviations from the long-term average vary with season, duration, and
threshold. The effects of climate variations are most readily detected for
the highest thresholds. Deviations from the long-term average tend to be
larger for frequencies than for magnitudes, and changes in frequency and
magnitude may have opposite signs.
Investigations presented in this paper show that variations in frequency and
magnitude of events at daily durations are a poor indicator of changes at
sub-daily durations. Studies like the one presented here should be
undertaken for other regions to allow the identification of regions with significant
increase/decrease in intense rainfall, whether there are common features
with regards to duration and season exhibiting most significant changes
(which in turn could lead to establishing a theoretical framework), and
assist in validation of projections of rainfall extremes. |
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