 |
| Titel |
An operational hydrological ensemble prediction system for the city of Zurich (Switzerland): skill, case studies and scenarios |
| VerfasserIn |
N. Addor, S. Jaun, F. Fundel, M. Zappa |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 15, no. 7 ; Nr. 15, no. 7 (2011-07-20), S.2327-2347 |
| Datensatznummer |
250012897
|
| Publikation (Nr.) |
 copernicus.org/hess-15-2327-2011.pdf |
|
|
|
|
|
| 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 limited-area atmospheric
forecasts provided by the deterministic model COSMO-7 and the probabilistic
model COSMO-LEPS. These atmospheric forecasts 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 to compare 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 reforecast was made
for the period June 2007 to December 2009 for the Sihl catchment
(336 km2). Several metrics support the conclusion that the performance
gain can be of up to 2 days lead time for the catchment considered. Brier
skill scores show that overall COSMO-LEPS-based hydrological forecasts outperforms
their COSMO-7-based 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, as shown by comparisons with a reference run
driven by observed meteorological parameters. Our evaluation stresses that
the capacity of the model to provide confident and reliable mid-term
probability forecasts for high discharges is limited. The two most intense
events of the study period are investigated utilising a novel graphical
representation of probability forecasts, and are used to generate high discharge
scenarios. They highlight challenges for making decisions on the basis of
hydrological predictions, and indicate the need for a tool to be used in
addition to forecasts to compare the different mitigation actions possible in
the Sihl catchment.
No definitive conclusion on the model chain capacity to forecast flooding events
endangering the city of Zurich could be drawn because of the under-sampling of
extreme events. Further research on the form of the reforecasts needed to infer on
floods associated to return periods of several decades, centuries, is encouraged. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|