EVALUATION OF A NON-HYDROSTATIC
MESOSCALE MODEL FOR DISCHARGE
FORECASTING
K. Chancibault, V. Ducrocq, F. Habets
CNRM/GAME, Météo-France
S. Anquetin, G-M. Saulnier
CNRS, LTHE
WSN05, Toulouse, France, 5-9 September 2005
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INTRODUCTION
•
Flash-floods in Southeastern France :
–
–
•
Quasi-stationnary MCS => high cumulative rainfall
amounts (>200 mm/day)
Small mountainous basins (200 – 2500 km²) => short lagtime (<12 hrs)
Next NWP models : non-hydrostatic high-resolution
model (AROME)
Meso-NH
or
AROME
Meteorological model
1-way
TOPMODEL
2-way
Hydrological model
1. One-way coupling : 8-9 September 2002 case
2. Two-way coupling : configuration
WSN05, Toulouse, France, 5-9 September 2005
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ONE-WAY COUPLING
• The hydrological model : TOPMODEL (Beven and
Kirkby, 1979)
–
–
–
–
–
–
DTM : 50 m
1 model / basin
9 basins (200 km²- 2200 km²)
Calibration (4 parameters)
Time step : 1 hour
Areal rainfall depths
ARDECHE
Vogüé
*
CEZE
GARD
St Martin
*
Alès
* La *
Anduze
Roque
* Boucoiran
Quissac*
*
Remoulins
*
*
VIDOURLE Sommières
WSN05, Toulouse, France, 5-9 September 2005
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ONE-WAY COUPLING
Rainfall data
• Simulated rainfall :
– Meso-NH (Lafore et al, 1998), non-hydrostatic
mesoscale model at 2.4 km
– Same physical package and resolution as AROME
– Initial conditions : mesoscale initialization
(surf obs + radar + IR sat data) from Ducrocq et
al ( 2000)
• Interpolated (kriging method) rain-gauge data
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ONE-WAY COUPLING
• Case study : 8-9 September 2002
– 24 casualties
– Damage : 1.2 billion euros
mm
10
Phase I
50
100
200
Phase II
+Nîmes
300
Phase III
+Nîmes
12-22 UTC,12-22
08/09/02
UTC 22-04 UTC, 08-09/09/02
22-04 UTC
Cumulated rainfall (Nîmes radar)
WSN05, Toulouse, France, 5-9 September 2005
+Nîmes
UTC
04-12 UTC,04-12
09/09/02
Delrieu et al (2005)
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ONE-WAY COUPLING
• Meso-NH simulations results
OBS
OBS
OBS
mm
Phase I: 12-22 UTC Phase II: 22-04 UTC Phase III: 04-12 UTC
SIMU
SIMU
Cumulated rainfall
WSN05, Toulouse, France, 5-9 September 2005
SIMU
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ONE-WAY COUPLING
• Meso-NH simulations results
Ardèche
mm
OBS
Cèze
 Rsim   Robs *100
 Rsim
Gard
Vidourle
SIMU
Cumulated rainfall during
the phase I
WSN05, Toulouse, France, 5-9 September 2005
Simulated rainfall depths
errors on the phase I
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ONE-WAY COUPLING
• Hydrological simulations results
Anduze (540 km²)
Vogüé (620 km²)
observed discharges
Simulated discharges from :
observed rainfall
simulated rainfall
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TWO-WAY COUPLING
• Configuration
t = 5 min
x = 2-3 km
L = 1000 km
Meso-NH
or Arome
flux
Wmob
t = 5 min
x = 2-3 km
L = 1000 km
ISBA
TOPMODEL
As
t = 1h
x = 50 m
L = 1 km
Routing
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TWO-WAY COUPLING
• Idealized simulation
Wg (t0 )  0.25 m 3 /m 3
Soil water horizontal
distribution
TOPMODEL 50m
Vogüé
 Wg  0.01 m3 /m 3
m3/m3
0.47
TOPMODEL 50m
Anduze
ISBA 2.5 km
0.45
0.43
Soil water
increment
+
0.41
0.39
Vogüé
0.37
0.35
0.33
coupleur
0.31
0.29
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+Anduze
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CONCLUSIONS AND OUTLOOKS
One-way coupling :
• Discharge forecasting needs updated high-resolution
forecasted rainfall
• Ensemble forecasting rainfalls to perform ensemble discharges
forecasting
Two-way coupling :
• Soil water horizontal distribution was implemented in the
SVAT scheme
• Soon, routing will be added  discharge simulation
• Sensitivity studies (e.g. time step, soil depth, …)
• Validation for numerous basins of the Southeastern France
Applications
 Validation of high-resolution simulated rainfall
 Study of the feedback of hydrology to the atmosphere
 Evaluation of the 2-way coupling vs the 1-way coupling
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