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EVALUATION OF A NON-HYDROSTATIC

MESOSCALE MODEL FOR DISCHARGE

FORECASTING

K. Chancibault, V. Ducrocq, F. HabetsCNRM/GAME, Météo-France

S. Anquetin, G-M. SaulnierCNRS, LTHE

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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 lag-time (<12 hrs)

Meso-NHor

AROMETOPMODEL

Meteorological model Hydrological model

1-way

2-way

1. One-way coupling : 8-9 September 2002 case

2. Two-way coupling : configuration

• Next NWP models : non-hydrostatic high-resolution model (AROME)

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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

ARDECHEARDECHE

CEZECEZEGARDGARD

VIDOURLEVIDOURLE

*Vogüé

*St Martin

*Quissac

*Sommières

*Remoulins

*Alès*

Anduze

*Boucoiran*La Roque

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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

5/10WSN05, Toulouse, France, 5-9 September 2005

ONE-WAY COUPLING

• Case study : 8-9 September 2002– 24 casualties– Damage : 1.2 billion euros

mm 10 50 100 200 300

12-22 UTC

+

12-22 UTC, 08/09/02

Phase I

Nîmes

22-04 UTC

+

22-04 UTC, 08-09/09/02

Phase II

Nîmes

04-12 UTC

+

04-12 UTC, 09/09/02

Phase III

Delrieu et al (2005)

Nîmes

Cumulated rainfall (Nîmes radar)

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ONE-WAY COUPLING

• Meso-NH simulations results mm

SIMU

OBS

Cumulated rainfall

Phase I: 12-22 UTC Phase II: 22-04 UTC

OBS

Phase III: 04-12 UTC

SIMU SIMU

OBS

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VidourleVidourle

GardGard

CèzeCèze

ArdècheArdèche

ONE-WAY COUPLING

• Meso-NH simulations results

mm

SIMU

OBS

Simulated rainfall depths errors on the phase I

Qui

ssac

So

mm

ière

s A

lès

And

uze

Bou

coir

anR

émou

lins

La

Roq

ue

Vog

üéSt

Mar

tin

100*obs

sim

sim

R

RR

Cumulated rainfall duringthe phase I

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ONE-WAY COUPLING

• Hydrological simulations results

Anduze (540 km²)

observed dischargesSimulated discharges from :

observed rainfallsimulated rainfall

Vogüé (620 km²)

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TWO-WAY COUPLING

• Configuration

Meso-NH or Arome

Routing

t = 5 minx = 2-3 kmL = 1000 km

ISBAt = 5 minx = 2-3 kmL = 1000 km

t = 1hx = 50 mL = 1 km

flux

TOPMODEL

Wmob

As

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TWO-WAY COUPLING

• Idealized simulation

TOPMODEL 50mVogüé

TOPMODEL 50m Anduze

Vogüé+

ISBA 2.5 km

Anduze+

330 /mm 25.0)( tWg

33/mm 01.0 Wg

Soil water horizontal distribution

coupleur

Soil waterincrement

0.47

0.45

0.43

0.41

0.39

0.37

0.35

0.33

0.31

0.29

m3/m3

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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