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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 - PowerPoint PPT Presentation
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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)