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Irina Gorodetskaya*, Hubert Gallée, Gerhard Krinner
Laboratoire de Glaciologie et Géophysique de l’Environnement, Grenoble,France
*Now at: Katholieke Universiteit Leuven, Belgium
CHARMANT, LGGE 19 October, 2009
Comparison of surface mass balance components simulated by LMDZ
and MAR forced with LMDZ
SMB compilationsVaughan et al. 1999Giovinetto and Bentley 1985
van den Berg et al. 2006:observations
van den Berg et al. 2006:calibrated model
166 mmwe
171 mmwe
Changes in precipitation?
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Linear trends of annual snowfall accumulation(mm yr -1 decade -1) for 1955-2004
Monaghan et al 2008
Predicted precipitation change: LMDZ (IPSL)
Krinner et al. 2007, 2008
Precipitation change: 2081-2100 / 1981-2000
SIC changes: (2081-2100) - (1981-2000)
Large-scale model (ECMWF or GCM)
Mesoscale model (MAR)
Nesting: MAR forced with LMDZ output
Atmospheric model: mesoscale hydrostatic primitive equation model (Gallée 1994, 1995)
Terrain following vertical coordinates (normalized pressure) Turbulence: 1 1/2 closure (Duynkerke 1988) Bulk cloud microphysics (Kessler 1962 and Lin et al 1983 + improvements of Meyers et al. 1992 and Levkov et al. 1992) Solar and infrared radiative transfer scheme (Morcrette 2002, Ebert and Curry 1992) Snow fall included into infrared radiation scheme
Snow model: conservation of heat and water (solid and liquid), description of snow properties (density, dendricity, sphericity and size of the grains), melting/freezingBlowing snow model (Gallée et al, 2001)
FS
FS
FL T4 HLatHSen
Sn
ow
HMelt HFreez
HCond
Tsfc
Pe
rco
lati
on
Liquid water
Blowingsnow
coupling to sea ice, land ice, vegetation...
Horizontal resolution 40 km 33 vertical levels (lowest ~9m, one level each 10 m below 50 m; top = 10hPa) Initial and boundary conditions: LMDZ4
Modèle Atmosphérique Régional (MAR)
Relative annual mean precipitation change:
Krinner et al. 2007
LMDZ (IPSL): 2081-2100 / 1981-2000
MAR (lmdz forced): 2082 / 1982
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Surface mass balance, mm w.e. 1981-1989
MAR (lmdz forced) LMDZ
175 mmwe42 mmwe
Ratio between simulated SMB in S20 and estimates by Vaughan et al. 1999
Ratio between LMDZ-simulated SMB and observed SMB in selected locations
Krinner et al. 2007
SMB components: LMDZ
1981-1989
Snow fall Sublimation surface
Total melt
units: mmwe
Effective melt
220 mmwe17 mmwe
29 mmwe
SMB components: MAR
1981-1989
Snow fall minus erosion Sublimation surface
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Melt
Sublimation drifting snow
units: mmwe
62 mmwe 14 mmwe
5 mmwe
7 mmwe
Annual snow fall, mmweDifference: MAR-LMZ
1981-1989
LMDZ: 220 mmwe
MAR: 62 mmwe
MAR-LMDZ: -128 mmwe
MAR : removal by wind erosion
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Blowing snow fluxSnow fall minus erosion
Surface sublimation/deposition
MEAN = 14 mmwe/yr
MAR, 1981-1989: ECMWF ERA-15, 1979-1993Déry and Yau, 2002
MEAN = 14 mmwe/yr
Sublimation of drifting snow
MEAN = 6 mmwe/yr
MAR, 1981-1989,Liu et al 1983 parametrization:
ECMWF ERA-15, 1979-1993Déry and Yau, 2002
MEAN = 15 mmwe/yr
Ablation areas
MAR SMB,mmwe/yr
Ablation areasvan den Broeke et al, 2006
Blue = Blue ice areas > 10%(Winther et al. 2001)Red diam = meteorite sites
AIS
Conclusions
• LMDZ and MAR : large differences in SMB
• LMDZ: - large precipitation and large melt = compensate- only two processes: precip and surface sublimation- melt calculated offline
• MAR: - snow fall is corrected for erosion = impossible to separate- lack of snow fall or too much erosion by wind- additional ablation processes: snow drift sublimation- melt is simulated
large local differences two models especially over the coasts need more observations to tell which one is right
Surface mass balance from a GCM:Laboratoire de Meteorologie Dynamique
general circulation model (LMDZ)
Krinner et al. 2007
mmwe1981-2000(S20)
SMB components: LMDZ 1981-2000
Melt
PrecipSublimation/deposition
Krinner et al. 2007
mmwe
Annual mean precipitation: MAR(lmdz forced) - LMDZ
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LMDZ: only snow fall(no erosion)
MAR: precip-erosion(blowing snowparameterization)
1980-1985
mmwe
Gallée and Gorodetskaya, Clim Dyn 2008
Surface air temperature over Dome C, East Antarctica
MAR validation : Dome C (ECMWF forcing)
Model validation : South Pole (ECMWF forcing)
Power spectrum (units2/time)
Town, Gorodetskaya, Walden, Warren, in prep
warm events
Sno
w a
ccum
ulat
ion,
mm
.w.e
Inte
grat
ed s
now
,m
m.w
.e
Snow accumulation at South Pole (MAR forced with ERA-40)
1994
PSCs Gorodetskaya, T
own, G
allée, in prep
54%
24%7%
11%4%
MAR forced with LMDZ vs LMDZ itself :
MAR - larger amplitude!
r=0.6
SMB changes: from 1982 to 2082
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Diff: 2082-1982
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Ratio: 2082/1982
MAR forced with LMDZ
mmwe
Relative annual mean precipitation change:
Krinner et al. 2007
LMDZ (IPSL): 2081-2100 / 1981-2000
MAR (lmdz forced): 2082 / 1982
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Annual mean surface temperature change: 2082-1982
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Precipitation change: 2082/1982 ratio
MAR forced with LMDZ
Annual mean sea ice concentration change
LMDZ [2081-2100] - [1981-2000]
%
Krinner et al. 2007