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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. Global Mean Sea Level Variations from Altimetry in mm. Steric effect: thermal expansion of the oceans

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model results of change in land water storage and effects on sea level
Model Results of change in Land Water Storage and Effects on Sea-Level

Katia Laval

Université Pierre et Marie Curie. Paris

LMD/IPSL

causes of sea level variations

Steric effect: thermal expansion of the oceans

water mass exchanged with other reservoirs: atmospheric water vapor and land water

Causes of sea level variations

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.

outline
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.
land surface models

W

Land Surface Models

P

ET

S

R

Precipitation (rain or snow): prescribed

Evapotranspiration (Rad Meteor parameters and vegetation and wetness)

Runoff

Snow melt

Storages

W: soil moisture

S: Snow depth

slide6

Land Surface Models

SOIL

ET

P

B

B’

I

Soil Hydrology

R

D

Irrigation

Flood plains

Runoff Routine

and ground water

B’

B (SB)

Qin

Qout = Q’in

Q1out

V1

Q2out

R

V2

fast

D

Q3out

slow

V3

Orchidee; Runoff Routine scheme: Jan Polcher ;Tristan D’Orgeval

slide7

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)

(Snow+soil water+ground water)

  • The differences could be due to :
    • incompatibility of the compared periods
    • data/model uncertainties
lmd agcm simulations orchidee amip simulation 79 99 sst
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)

climate model biases in seasonality revealed by satellite gravimetry swenson and milly 2005 wrr
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.

slide10

Global map of amplitude (mm) of annual cycle of land water storage from GRACE

and from five climate models. (Swenson and Milly, 2005, WRR)

slide11

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

slide12

Time series of water storage variationas 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.

slide13

Construction of NCC data

NCEP/NCAR Reanalysis

6h; 1°.875; 1948-present

Interpolation to the grid 1°x1°, differences in

elevation between the grids were taken into account

NCEP

CRU (Climate Research Unit)precipitation

0.5°x 0.5°, 1901-2000

NPRE

CRU (Climate Research Unit) temperature

0.5°x 0.5°, 1901-2000

NCRU

Radiation: SRB (Surface Radiation Budget)

NCC

(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)

effect of global land water storage on global mean sea level

agreement between ORCHIDEE and LaD.

  • (Land Dynamics LSM of GFDL)
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)

relations between land water and thermosteric sea level fluctuations
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

conclusions
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
conclusions1
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
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