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/CNRS2Météo-France, Direction de la Climatologie

EGU General Assembly 2009, 20-24 April 2009

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

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)

Safran

atmospheric analysis system

Optimal Interpolation of ERA-40 + ground observations

Gridded rainfall, snowfall, temperature, humidity, wind speed, visible, infrared radiation (8km, hourly)

Isba

land surface scheme

Computation of water and energy budgets with soil and vegetation databases (ECOCLIMAP)

Evapotranspiration, soil moisture, snow cover, drainage, runoff, etc. (8km, 5 min)

Drainage and runoff

Modcou

hydrogeological model

Flow routing, multilayer aquifers

Flow (3-hourly) and water table levels (1-8km)

wiltfc

wilt

ww

wwSWI

– w : water content

– wwilt : wilting point

– wfc : field capacity

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

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

Variable Drought type

Safran Precipitation Meteorological

Isba Soil Wetness Index Agricultural

Modcou River flow Hydrological

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

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

Autumn 19781976 1989-1990 2003

SPI3

SSWI3

SFI3

SP

I3

020

40

60

80

100

SS

WI3

020

40

60

80

100

020

40

60

80

100

SF

I3

1960 1970 1980 1990 2000

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

SFI3

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

SSWI3

Example of drought propagation

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

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Long start Heart Recovery

Soil memory

“Extremely wet” flow conditionspropagating downstream

Loire and Allier rivers

Heavy convective rainfallon rather dry soil

High runoff

extreme droughtsevere droughtmoderate droughtmild droughtmildly wetmoderately wetseverely wetextremely wet

Extreme droughtSevere droughtModerate droughtMild droughtMildly wetModerately wetSeverely wetExtremely wet

Soil and vegetationresistance

SPI3

From indices to events – Local scale

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

-2.0

-1.0

0.0

0.5

1.0

1.5

SS

WI3

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Duration

Severity

MagnitudeThreshold

P = 5%

Starting date

Peak date

End date

Some local characteristics

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

Number of events

5

10

15

20

25

30

35

40

Mean duration (months)

5

10

15

20

Most frequent starting month

2

4

6

8

10

12

Urban areasSandy soils with cropsSandy soils with forests Autumn starting droughtsWinter starting droughtsSpring droughts

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 characteristics1. [Duration, severity, magnitude] combined with area

Mean characteristics

0 10 20 30 40 50 60 70

51

01

5

Mean area (%)

Me

an

du

ratio

n (

mo

nth

s)

Jan 1976 - Oct 1976

Oct 1978 - May 1979Sep 1985 - Mar 1986

Oct 1988 - Dec 1990

Mar 1997 - Aug 1997

Mar 2003 - Oct 2004Nov 2004 - Apr 2006

Meanduration(months)

SSWI3

P=20%

Mean area (% of France)

Mean severity

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 characteristics1. [Duration, severity, magnitude] combined with area

2. 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)

0 20 40 60 80 100

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

Area (%)

Nov 1975 - Oct 1976Aug 1978 - Jan 1979

0 20 40 60 80 1001.

41.

61.

82.

02.

22.

42.

62.

8

Area (%)

Dec 1975 - Dec 1976Sep 1978 - Feb 1979

0 20 40 60 80 100

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

Area (%)

Mar 1975 - Apr 1977

0 20 40 60 80 100

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

Jan 1976 - Oct 1976Oct 1978 - May 1979Oct 1988 - Dec 1990Mar 1997 - Aug 1997

0 20 40 60 80 100

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

Feb 1971 - Aug 1972Apr 1976 - Dec 1976Oct 1985 - Apr 1986Nov 1988 - Feb 1991May 2003 - Jul 2008

0 20 40 60 80 1001.

41.

61.

82.

02.

22.

42.

62.

8

Jan 1989 - Mar 1993

SAT curves of most severe events

Severity

SPI3 SPI6 SPI12

Area (%)

SSWI3 SSWI6 SSWI12

P=20%

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

Conclusions

Further work

Evolution of drought characteristics under climate change

Dealing with uncertainty1. Emissions scenarios

• A1B• A2

2. Range of climate models• Transient projections from different versions of ARPEGE• Time slices from IPCC AR4 models

3. Two downscaling methods• Weather types (Boé et al., 2006)• Quantile-quantile (Déqué, 2007)

Thank you for your attention

Contact:

jean-philippe.vidal@meteo.fr

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