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| Titel |
An operational hydrological ensemble prediction system for the city of Zurich (Switzerland): assessing the added value of probabilistic forecasts |
| VerfasserIn |
N. Addor, S. Jaun, F. Fundel, M. Zappa |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250063176
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| Zusammenfassung |
| The Sihl River flows through Zurich, Switzerland’s most populated city, for which it
represents the largest flood threat. To anticipate extreme discharge events and provide
decision support in case of flood risk, a hydrometeorological ensemble prediction system
(HEPS) was launched operationally in 2008. This model chain relies on deterministic
(COSMO-7) and probabilistic (COSMO-LEPS) atmospheric forecasts, which are used to
force a semi-distributed hydrological model (PREVAH) coupled to a hydraulic model
(FLORIS). The resulting hydrological forecasts are eventually communicated to the
stakeholders involved in the Sihl discharge management.
This fully operational setting provides a real framework with which we assessed the
potential of deterministic and probabilistic discharge forecasts for flood mitigation. To study
the suitability of HEPS for small-scale basins and to quantify the added value conveyed by
the probability information, a 31-month reforecast was produced for the Sihl catchment
(336Â km2). Several metrics support the conclusion that the performance gain is of
up to 2Â days lead time for the catchment considered. Brier skill scores show that
probabilistic hydrological forecasts outperform their deterministic counterparts
for all the lead times and event intensities considered. The small size of the Sihl
catchment does not prevent skillful discharge forecasts, but makes them particularly
dependent on correct precipitation forecasts. Our evaluation stresses that the capacity
of the model to provide confident and reliable mid-term probability forecasts for
high discharges is limited. We finally highlight challenges for making decisions on
the basis of hydrological predictions, and discuss the need for a tool to be used in
addition to forecasts to compare the different mitigation actions possible in the Sihl
catchment. |
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