Multilevel drought reanalysis over france with safran isba modcou hydrometeorological suite
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Multilevel drought reanalysis over France with Safran-Isba-Modcou hydrometeorological suite. Jean-Philippe Vidal 1 , É ric Martin 1 , Laurent Franchistéguy 2 , Jean-Michel Soubeyroux 2 , Martine Baillon 2 and Michèle Blanchard 2 1 CNRM/GAME, Météo-France/CNRS

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Multilevel drought reanalysis over France with Safran-Isba-Modcou hydrometeorological suite

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Multilevel drought reanalysis over france with safran isba modcou hydrometeorological suite

Multilevel drought reanalysis over France with Safran-Isba-Modcou hydrometeorological suite

Jean-Philippe Vidal1, Éric Martin1,

Laurent Franchistéguy2, Jean-Michel Soubeyroux2, Martine Baillon2 and Michèle Blanchard2

1CNRM/GAME, Météo-France/CNRS

2Météo-France, Direction de la Climatologie

EGU General Assembly 2009, 20-24 April 2009


Contents

Contents

  • ClimSec project

  • Tools and methods

    • Safran-Isba-Modcou

    • Drought indices

  • Overview of drought patterns

    • Spatial extension

    • Propagation through the hydrological cycle

  • From indices to events

    • Local scale

    • National scale

  • Conclusions and further work


Climsec project

ClimSec project

  • 2-year project: “Impact of climate change on drought and soil moisture in France”

  • Motivated by damages to buildings following 2003 drought due to soil shrinking and swelling; Aims at finding whether such events will be more frequent in the future

  • Funded by Fondation MAIF

  • Partners:

    • Météo-France, Climatology Department

    • CNRM/GAME

    • CERFACS

    • UMR Sisyphe

  • Focus on the reanalysis of drought events for characterizing present climate


Safran isba modcou sim

50-year SIM

hydrometeorological reanalysis

(1 August 1958 to 31 July 2008)

Vidal et al. (submitted) A 50-year high-resolution atmospheric reanalysis over France with Safran system. International Journal of Climatology

Safran-Isba-Modcou (SIM)

  • w : water content

  • wwilt : wilting point

  • wfc : field capacity


Drought indices

Drought indices

  • Drought : abnormal water deficit in one (or more) part of the land surface hydrological cycle

  • Choice of relevant drought indices depends on the socio-economic activity domain

    No universal drought index

  • SIM: consistent computation of variables within the hydrological cycle


Drought indices1

Drought indices

  • Approach

    • Use of a monthly variable summed/averaged over n months

    • Kernel density estimates for each calendar month and grid cell

    • Quantile-quantile projection onto normal distribution

  • Advantages

    • Computation with reference to 50-year local climate

    • Correspondance index value / non-exceedance probability

    • Spatial consistency

    • Different time scales: 1 to 24 months

  • Indices

    • Standardized Precipitation Index (SPI) → 8km grid

    • Standardized Soil Wetness Index (SSWI) → 8km grid

    • Standardized Flow Index (SFI) → >900 hydrometric stations


Overview of dry periods

Autumn 1978

1976

1989-1990

2003

Overview of dry periods

Area affected by drought (% of France area), 3-month indices, threshold 5%

SPI3

SSWI3

SFI3


Example of drought propagation

SSWI3

Long start

Heart

Recovery

SFI3

Soil and vegetation

resistance

Soil memory

Extreme drought

Severe drought

Moderate drought

Mild drought

Mildly wet

Moderately wet

Severely wet

Extremely wet

“Extremely wet” flow conditions

propagating downstream

Loire and Allier rivers

Heavy convective rainfall

on rather dry soil

 High runoff

Example of drought propagation

SPI3

  • Year 1976, 3-month indices, traditional SPI drought classes


From indices to events local scale

End date

Starting date

Duration

Magnitude

Severity

Peak date

From indices to events – Local scale

Grid cell located near Toulouse (south-west), SSWI3

Threshold

P = 5%


Some local characteristics

Autumn starting droughts

Winter starting droughts

Spring droughts

Urban areas

Sandy soils with crops

Sandy soils with forests

Some local characteristics

  • 50-year analysis of SSWI1, threshold P = 10%


From indices to events national scale

From indices to events – National scale

  • Droughts are developping in both space and time

  • Event identification

    • Event envelop: index threshold (ex: P=20%)

    • Spatial contiguity: cluster identification at each time step

    • Temporal continuity: minimum common area between two time steps

  • Spatio-temporal characteristics

    • [Duration, severity, magnitude] combined with area


Mean characteristics

Mean characteristics

SSWI3

P=20%

Mean severity

Mean

duration

(months)

Mean area (% of France)


From indices to events national scale1

From indices to events – National scale

  • Droughts are developping in both space and time

  • Spatio-temporal event identification

    • Event envelop: index threshold (ex: P=20%)

    • Spatial contiguity: cluster identification at each time step

    • Temporal continuity: minimum common area between two time steps

  • Spatio-temporal characteristics

    • [Duration, severity, magnitude] combined with area

    • Identification of most severe events through

      Severity–Area–Time Scale(SAT) curves inspired from depth-area-duration analysis of storm precipitation (WMO, 1969; Andreadis et al., 2005)


Sat curves of most severe events

SAT curves of most severe events

SPI6

SPI3

SPI12

P=20%

Severity

SSWI3

SSWI6

SSWI12

Area (%)


Conclusions

Conclusions

  • Safran-Isba-Modcou hydrometeorological suite

    • Consistent approach for monitoring drought propagation through the hydrological cycle

  • Standardized drought indices

    • Powerful analysis tools for characterizing events in space and time

  • Drought reanalysis

    • Identification and description of past drought events at both local and national scale in France


Further work

Further work

  • Evolution of drought characteristics under climate change

  • Dealing with uncertainty

    • Emissions scenarios

      • A1B

      • A2

    • Range of climate models

      • Transient projections from different versions of ARPEGE

      • Time slices from IPCC AR4 models

    • Two downscaling methods

      • Weather types (Boé et al., 2006)

      • Quantile-quantile (Déqué, 2007)


Thank you for your attention

Contact:

[email protected]

1988-1990 SSWI3 drought (envelop P=20%)

Thank you for your attention


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