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Comparison of surface mass balance components simulated by LMDZ and MAR forced with LMDZ

Comparison of surface mass balance components simulated by LMDZ and MAR forced with LMDZ. Irina Gorodetskaya * , Hubert Gall é e, Gerhard Krinner Laboratoire de Glaciologie et G é ophysique de l’Environnement, Grenoble,France * Now at: Katholieke Universiteit Leuven, Belgium.

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Comparison of surface mass balance components simulated by LMDZ and MAR forced with LMDZ

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  1. Comparison of surface mass balance components simulated by LMDZ and MAR forced with LMDZ 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

  2. Vaughan et al. 1999 Giovinetto and Bentley 1985 SMB compilations 166 mmwe van den Berg et al. 2006: observations van den Berg et al. 2006: calibrated model 171 mmwe

  3. Changes in precipitation? Linear trends of annual snowfall accumulation (mm yr -1 decade -1) for 1955-2004 Monaghan et al 2008

  4. Predicted precipitation change: LMDZ (IPSL) Precipitation change: 2081-2100 / 1981-2000 SIC changes: (2081-2100) - (1981-2000) Krinner et al. 2007, 2008

  5. Large-scale model (ECMWF or GCM) Nesting: MAR forced with LMDZ output Mesoscale model (MAR)

  6. Snow HCond FL T4 HLat FS HSen coupling to sea ice, land ice, vegetation...  HMelt HFreez Blowingsnow     FS        Tsfc Liquid water Percolation 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/freezing Blowing snow model (Gallée et al, 2001) Modèle Atmosphérique Régional (MAR) • Horizontal resolution 40 km • 33 vertical levels (lowest ~9m, one level each 10 m below 50 m; top = 10hPa) • Initial and boundary conditions: LMDZ4

  7. Relative annual mean precipitation change: LMDZ (IPSL): 2081-2100 / 1981-2000 MAR (lmdz forced): 2082 / 1982 Krinner et al. 2007

  8. Surface mass balance, mm w.e. 1981-1989 MAR (lmdz forced) LMDZ 42 mmwe 175 mmwe

  9. 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

  10. Snow fall Sublimation surface SMB components: LMDZ1981-1989 220 mmwe 17 mmwe Total melt Effective melt 29 mmwe units: mmwe

  11. Sublimation surface Melt Snow fall minus erosion SMB components: MAR 1981-1989 14 mmwe 62 mmwe Sublimation drifting snow 7 mmwe 5 mmwe units: mmwe

  12. LMDZ: 220 mmwe Annual snow fall, mmweDifference: MAR-LMZ1981-1989 MAR-LMDZ: -128 mmwe MAR: 62 mmwe

  13. Blowing snow flux MAR : removal by wind erosion Snow fall minus erosion

  14. Surface sublimation/deposition ECMWF ERA-15, 1979-1993 Déry and Yau, 2002 MAR, 1981-1989: MEAN = 14 mmwe/yr MEAN = 14 mmwe/yr

  15. Sublimation of drifting snow MAR, 1981-1989, Liu et al 1983 parametrization: ECMWF ERA-15, 1979-1993 Déry and Yau, 2002 MEAN = 6 mmwe/yr MEAN = 15 mmwe/yr

  16. Ablation areas MAR SMB, mmwe/yr Ablation areas van den Broeke et al, 2006 AIS Blue = Blue ice areas > 10% (Winther et al. 2001) Red diam = meteorite sites

  17. 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

  18. Surface mass balance from a GCM:Laboratoire de Meteorologie Dynamique general circulation model (LMDZ) 1981-2000 (S20) mmwe Krinner et al. 2007

  19. SMB components: LMDZ 1981-2000 mmwe Sublimation/ deposition Precip Melt Krinner et al. 2007

  20. Annual mean precipitation: MAR(lmdz forced) - LMDZ 1980-1985 LMDZ: only snow fall (no erosion) MAR: precip-erosion(blowing snow parameterization) mmwe

  21. MAR validation : Dome C (ECMWF forcing) Surface air temperature over Dome C, East Antarctica Gallée and Gorodetskaya, Clim Dyn 2008

  22. Model validation : South Pole (ECMWF forcing) Power spectrum (units2/time) Town, Gorodetskaya, Walden, Warren, in prep

  23. Snow accumulation at South Pole (MAR forced with ERA-40) Integrated snow,mm.w.e Snow accumulation, mm.w.e warm events PSCs 54% 24% 7% 4% 11% Gorodetskaya, Town, Gallée, in prep 1994

  24. MAR forced with LMDZ vs LMDZ itself : MAR - larger amplitude! r=0.6

  25. Diff: 2082-1982 MAR forced with LMDZ SMB changes: from 1982 to 2082 Ratio: 2082/1982 mmwe

  26. Relative annual mean precipitation change: LMDZ (IPSL): 2081-2100 / 1981-2000 MAR (lmdz forced): 2082 / 1982 Krinner et al. 2007

  27. MAR forced with LMDZ Annual mean surface temperature change: 2082-1982 Precipitation change: 2082/1982 ratio

  28. Annual mean sea ice concentration changeLMDZ [2081-2100] - [1981-2000] % Krinner et al. 2007

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