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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)

7

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