Model Results of change in Land Water Storage and Effects on Sea-Level
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Transcript of Model Results of change in Land Water Storage and Effects on Sea-Level
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Sea Level Rise 2006
Model Results of change in Land Water Storage and Effects on
Sea-Level
Katia Laval Université Pierre et Marie Curie. Paris LMD/IPSL
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Global Mean Sea Level Variations from Altimetry in mm
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Causes of sea level variationsCauses of sea level variations Steric effect: thermal expansion of the oceans water mass exchanged with other reservoirs:
atmospheric water vapor and land water
Sea level variations evaluated by T/P for 1993-98 (Black), steric effect evaluated from Ishii et al, 2003, water vapor contribution from NCEP reanalysis and residual signal.
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Outline
• Land Surface Models• Seasonal Variations of Global Sea level;
Interannual variability (1997/1998)• Seasonal Variations of Regional land water
(GRACE)• Trend of sea level height during the last 53 years
related to terrestrial water storage.
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Land Surface Models
W
P ET
R
S
Storages
W: soil moisture
S: Snow depth
Precipitation (rain or snow): prescribed
Evapotranspiration (Rad Meteor parameters and vegetation and wetness)
Runoff
Snow melt
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SOIL
P
RI
B B’
D
B (SB) B’
R
D
QinQ1
out
Q2out
Q3out
Qout = Q’in
ET
Runoff Routine and ground water
Soil Hydrology
V1
V2
V3
IrrigationFlood plains
Land Surface Models
Orchidee; Runoff Routine scheme: Jan Polcher ;Tristan D’Orgeval
fast
slow
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GSWP1: Evaluation of seasonal variation of land water by LSP
ISLSCP-I International Satellite Land-Surface Climatology Project, produced the atmospheric forcing
over the continents for 1987 and 1988
Seasonal variations of SLH evaluated by T/P and 3 LSM: LaD (GFDL), ISBA Meteo-France, Orchidee (LMD/IPSL)
(Snow+soil water+ground water) The differences could be due to :
incompatibility of the compared periods data/model uncertainties
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LMD AGCM Simulations (+Orchidee): AMIP Simulation (79-99 SST)LMD AGCM Simulations (+Orchidee): AMIP Simulation (79-99 SST)
Contribution of continental water to sea level variations
Precipitations computed by the GCM Ngo-duc, T., K. Laval, J. Polcher and A. Cazenave (JGR, 2005a)
•Sharp contrast 1997 /1998 (Willis et al, 2004): Observations from T/P: 13mm compared to 7mm (10mm/7mm) •The variation between 1998 and 1997 is larger than internal variability
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Climate-Model Biases in Seasonality revealed
by Satellite Gravimetry (Swenson and Milly, 2005, WRR)
Models evaluated in this study and water stores used. “X” indicates presence of term; “0” indicates absence from model.
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Global map of amplitude (mm) of annual cycle of land water storage from GRACE and from five climate models. (Swenson and Milly, 2005, WRR)
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.
Seasonal Variations (April-May minus November 2002) of land water in mm
From GRACE
Orchidee without Ground Water reservoir
Orchidee with Ground Water reservoir
Ngo-duc, et al, 2006, submitted,WRR.
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Time series of water storage variation as simulated by 2 versions of Orchidee, with and without routine scheme and ground water scheme and evaluated by Grace Mission (o).
Ngo-duc, et al, 2006, submitted, WRR.
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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°x1°, differences in
elevation between the grids were taken into account
CRU (Climate Research Unit) precipitation
0.5°x 0.5°, 1901-2000
CRU (Climate Research Unit) temperature
0.5°x 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, 2005b)
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Effect of global land water storage on global mean sea level
agreement between ORCHIDEE and LaD.(Land Dynamics LSM of GFDL)
greatest variation is associated with ground water, followed by soil moistureno significant
trend was detected strong decadal
variability driven by precipitation, strong decrease in the beginning of 1970s
Milly, P. C., D., A. Cazenave, and M. C. Gennero (Proc. Natl Acad. Sci, 2003)
Ngo-duc T., K. Laval, J. Polcher, A. Lombard and A. Cazenave (GRL, 2005)
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Relations between land water and thermosteric sea level fluctuations
These results suggest a feedback mechanism: Ocean warmer more evaporation and continental precipitation increases
continents are wetter: sea-level height decreases
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Conclusions
• The LSMs are able to simulate the seasonal variations of global land water storage, and
some interannual variability is also captured by LSMs and GCMs
• We need more studies to strengthen our results on regional seasonal variations
- LSMs models: we must improve the reservoirs representation (lakes, dams, processes)- Grace data for several years
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Conclusions
• Trends of terrestrial water storage have to be ascertained :
- NCC data used by other LSMs
- Other data (Qian et al, 2006)
- Results on last years with Grace
• Influence of anthropogenic changes