A. Amengual and V. Homar
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Transcript of A. Amengual and V. Homar
Hydrometeorological ensemble forecasts for the 28 September 2012 (IOP8) extreme flash-
flood in Murcia, Spain
A. Amengual and V. Homar
Grup de Meteorologia, Departament de Física, Universitat de les Illes Balears,
Palma, Mallorca, Spaine-mail: [email protected]
Universitat de les Illes Balears Reunión PREDIMED 2014A5-6 Junio
Hydrometeorological ensemble forecasts for the 28 September 2012 (IOP8) extreme flash-flood in Murcia,
Spain
1. The Guadalentín flash-flood event
2. Hydrological and meteorological tools
3. Probabilistic versus deterministic QPFs
4. Probabilistic versus deterministic QDFs
5. Conclusions and further remarks
1. The Guadalentín flash-flood event: synoptic situation
• Entrance of a deep upper-level closed trough • Generation of a surface mesoscale cyclone • Advection of warm and moist air toward Almería and Murcia from the Mediterranean
Convergence zone between easterly advection and westerly low-level flow+ orographic enhancement
quasi-stationary mesoscale convective system
H500+T500+PV250
T850+SLP
27 September 2012 12 UTC 28 September 2012 12 UTC
• Torrential precipitation took place on 27, 28 and 29 September 2012
• Daily precipitation amounts: 214 mm in Andalucía, 240 mm in Murcia and 230 mm in Valencia
• The Guadalentín catchment is a medium size basin with an area of 3343 km2 and a length close to 121 km
• Accumulated rainfall in 8 h up to 214 mm inside the basin
• Peak discharges: - 616.3 m3s-1 in Lorca- 1081.2 m3s-1 in Paretón de Totana
1. The Guadalentín flash-flood event: observations
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1. The Guadalentín flash-flood event
• 10 casualties. Material losses estimated at about 120 M€
2. Hydrological and meteorological tools
WRF model set-up
• Initial and boundary conditions: ECMWF forecasts (update 6h, 0.3º; 62 vertical levels)
• One domain: 4 km and 28 vertical eta-levels
• Schemes: Microphysics ─ WSM6; Long-wave radiation ─ RRTM ; Short wave radiation ─ Dudhia; surface model ─ NOAH; time-step ─ 30 s
• The experiments consider a 48 h period simulation (27/09/2012 - 29/09/2012 00 UTC)
HEC-HMS model set-up
• Loss rate: Soil Conservation Service Curve Number (SCS-CN) model
• Transform: SCS Unit Hydrograph model
• Flow routing: Muskingum method
• Reservoirs: elevation-storage-outflow relationship + initial elevation of the water level
• The experiments consider a 72 h period simulation (27/09/2012-01/10/2012 00 UTC)
2. Hydrological and meteorological tools
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MEDITERRANEAN SEA
SPAIN
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Iberian system
M urciaCHS
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3. Probabilistic versus deterministic QPFs
Difficulties to correctly forecast precise location and timing of convectively-driven rainfall system affecting a medium size basin
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EV (%)
-89.90.12control
-2.60.91rain-gauges
EP (%)NSEGuadalentín
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(b) Paretón (2384.7 km2)
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Flow observations only available for this study case: perfect-model assumption. Optimal estimation of the initial conditions and dynamical formulation after calibration.
3. Probabilistic versus control QPFs
Mesoscale EPS (WRF)
• Diversity source only from IC/BC (dynamical downscaling)
• Obtained from ECMWF-EPS forecast (Global Singular Vectors)
• 50 equally-likely members
Study of the spatial and temporal uncertainties of QPFs into a medium-sized catchment
(d) Probability-matched ensemble mean
• WRF ensemble comprises 51 elements (control + 50 perturbed)
• Important spread on rainfall values
• Essential role of atmospheric dynamical forcing
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(c) Ensemble mean ( in mm, shaded) and standard deviation (in mm, continuous line starting at 10 mm interval)
3. Probabilistic versus control QPFs
4. Probabilistic versus deterministic QDFs
• Elements of the HEPS are considered equally-like
• Cumulative distribution functions (CDFs) of driven runoff peak flows
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4. Probabilistic versus deterministic QDFs
• Elements of the HEPS are considered equally-like
• Cumulative distribution functions (CDFs) of driven runoff peak flows
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observedcontro lensem bleensem ble m eanprobability-m atchedQ p(T=25 yrs)Q p(T=35 yrs)
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observedcontro lensem bleensem ble m eanprobability-m atchedQ p(T=25yrs)Q p(T=35yrs)
Paretón (2384.7 km 2)(b)
5. Conclusions and further remarks
• WRF control simulation is deficient for the Guadalentín event: maximum precipitation amounts are obtained quite far away from the basin
• EPS reduce biases obtained for the control forecast
• For civil protection purposes, a hypothetical first warning for a peak flow exceeding Qp (T = 25 yrs) would have produced a probability of exceedence of 0.4 and 0.3 at Lorca and Paretón. This fact points out the benefits of a HEPS versus a deterministic prediction system • The performance of the hydrometeorological simulations strongly depends on the
initial conditions of the databases and on the case under study
• References:
Amengual et al. (2014): Hydrometeorological ensemble forecasts for the 28 September 2012 (IOP8) extreme flash-flood in Murcia,Spain. Quart. J. R. Meteorol. Soc [submitted]