Model%20Results%20of%20change%20in%20Land%20Water%20Storage%20and%20Effects%20on%20Sea-Level

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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 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
P
ET
S
R
Precipitation (rain or snow) prescribed Evapotran
spiration (Rad Meteor parameters and vegetation
and wetness) Runoff Snow melt
Storages W soil moisture S Snow depth
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Land Surface Models
P
ET
B
B
I
Soil Hydrology
R
D
Irrigation Flood plains
Runoff Routine and ground water
B
B (SB)
Qin
Qout Qin
Q1out
V1
Q2out
R
V2
fast
D
Q3out
slow
V3
Orchidee Runoff Routine scheme Jan Polcher
Tristan DOrgeval
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GSWP1 Evaluation of seasonal variation of land
water by LSPISLSCP-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)
• (Snowsoil waterground 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)

• 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

• 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)

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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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From GRACE
Orchidee without Ground Water reservoir
Orchidee with Ground Water reservoir
Ngo-duc, et al, 2006, submitted,WRR.
.
Seasonal Variations (April-May minus November
2002) of land water in mm
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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 data
NCEP/NCAR Reanalysis
6h 1.875 1948-present
Interpolation to the grid 1x1, differences in
elevation between the grids were taken into
account
NCEP
CRU (Climate Research Unit) precipitation 0.5x
0.5, 1901-2000
NPRE

• CRU (Climate Research Unit) temperature
• 0.5x 0.5, 1901-2000

NCRU
Radiation SRB (Surface Radiation Budget)
NCC

• (NCEP/NCAR Corrected by CRU)
• 6-hourly, 1x1, 1948-2000
• http//dods.lmd.jussieu.fr/cgi-bin/nph-dods/Dods/N
  CC/ (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

• greatest variation is associated with ground
  water, followed by soil moisture
• no 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