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