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Variations of land water storage over the last half century
K. Laval, T. Ngo-duc, J. Polcher University PM Curie Paris/Lab Meteor Dyn /IPSL
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Land Water Balance
Variation of land water in Land Surface Models:
-Precipitation (highly variable)
-Melting of Snow and Ice
-Evapotranspiration
-Total Runoff
Runoff yields river discharge Y to the surface water
Network:integration over a basin
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Outline
• Construction of 53-year atmospheric data to force LSM Models
• Results on river discharges (Mekong): Seasonal and interannual variations
• Preliminary results on water storage (Grace Mission): Influence of inundated and irrigated areas
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The ORCHIDEE land surface model of IPSL SECHIBA : surface energy and water balances (land and
soil)STOMATE : surface biochemical processes
LPJ :evolution of the vegetation and the carbon budget
• Only Sechiba is used in the Only Sechiba is used in the simulations.simulations.
• Inclusion of a Inclusion of a routing routing schemescheme, which routes water , which routes water to oceans through a cascade to oceans through a cascade of linear reservoirs.of linear reservoirs.
• Ducoudre,N, K. Laval and A. Perrier, 1993: Ducoudre,N, K. Laval and A. Perrier, 1993: a new set of hydrological exchanges at the a new set of hydrological exchanges at the land atmosphere interface. J. of land atmosphere interface. J. of Climate,6248-273.Climate,6248-273.
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Forced simulation over 53 years
• Construction of 53-y forcing data and integrations of Land Surface Model
• Validation of river discharges
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Construction of NCC dataNCEP/NCAR NCEP/NCAR ReanalysisReanalysis
6h; 1°.875; 1948-present
NCEP
NPRE
NCRU
NCC
Interpolation to the grid 1°×1°, differences in
elevation between the grids were taken into account
CRU (Climate Research Unit) precipitation
0.5°×0.5°, 1901-2000
CRU (Climate Research Unit) temperature
0.5°×0.5°, 1901-2000
Radiation: SRB (Surface Radiation Budget)
(NCEP/NCAR Corrected by CRU)6-hourly, 1°x1°, 1948-2000
http://dods.lmd.jussieu.fr/cgi-bin/nph-dods/Dods/NCC/ (~40GB)
Ngo-duc, T., J. Polcher and K. Laval (JGR, 2005)
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Validation
The river discharge of the world's 10 biggest
rivers
Observed dischargeObserved discharge GRDC (Global Runoff Data Center) Data at UCAR (the University Corporation for Atmospheric Research)
Station Obidos 55.51°W,
1.95°S
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Amazon River Discharge
OBS
NCEP/NCAR
NCC
NCC
NCEP/NCAR
OBS
quality of the NCC forcing data is improved compared to NCEP/NCAR
high flow in simulated mean seasonal signal is too early
the interannual signal is well described by the NCC experiment
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Seasonal signal of Mekong discharge
at Pakse
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Annual Discharge simulated at Pakse
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Taylor diagram: Taylor diagram: NCEP and NCC
1. Amazon 2. Congo3. Orinoco4. Changjiang5. Brahmaputra
6. Mississippi7. Yenisey8. Parana9. Lena10. Mekong
Precipitation: most important improvement
Temperature: significant effect only at high
latitudes
Radiation: improves discharge amplitudes
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From Frappart et al submitted GJI.
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Irrigated and Inundated areas
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> 0.3 mm day-1
> 0.2 mm day-1
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Simulated Soil Moisture by Orchidee
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Mekong discharge at the mouth of the river
18500
16600
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GRACE Mission (Gravity Recovery And Climate ExperimentGRACE Mission (Gravity Recovery And Climate Experiment
• GRACE, twin satellites launched in March 2002, measure the Earth's gravity field with unprecedented accuracy. This produces estimates of changes in water storage for given terrestrial regions.
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Water storage variation as simulated by 2 versions of Orchidee (with and without routine scheme )
and evaluated by Grace Mission (o).
The routine scheme improves the simulated water storage
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Conclusions• Orchidee is able to reproduce seasonal and
interannual changes of continental water reservoirs.
• NCC data set was found reliable.• The influence of inundated and irrigated areas
seems substantial for the water budget of Mekong basin.
• Estimations from GRACE seem to confirm the role of ground water.
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GRACE ORCHIDEE with routing
ORCHIDEE without routing
Seasonal variations of continental water
April/May – November 2002
The routing scheme improves the signals over tropical basins