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Polar WRF over Antarctica

Polar WRF over Antarctica. Julien Nicolas. Performance of Polar WRF in the Antarctic. What has been done Series of 12-month simulations at 60 km resolution Different experimental setups: Model versions (v3.0.1, v3.1.1, v3.2.1) Different physics schemes: radiation (CAM, RRTM, RRTMG)

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Polar WRF over Antarctica

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  1. Polar WRF over Antarctica Julien Nicolas ACCIMA Project Meeting - 16 Dec 2011

  2. Performance of Polar WRF in the Antarctic What has been done • Series of 12-month simulations at 60 km resolution • Different experimental setups: • Model versions (v3.0.1, v3.1.1, v3.2.1) • Different physics schemes: • radiation (CAM, RRTM, RRTMG) • PBL (MYJ and MYNN) • Interannual variability (1993 versus 2007) • Model validation against: • Radiation (BSRN) • Radiosoundings (IGRA) • AWS and synoptic stations (NCDC) ACCIMA Project Meeting - 16 Dec 2011

  3. Performance of Polar WRF in the Antarctic What has been learned • Model skill comparable to that tested in the Arctic • Caveats: data coverage/quality, stations mostly on the coast • Performance doesn’t necessarily improve with model version • Surface & subsurface energy balance: • Excessive incoming SW radiation • Deficit in downwelling LW radiation • Cold bias in summer • Excessive SW radiation → Excessive sublimation • Warm bias in winter • Excessive sensible heat flux into the snowpack • Wind speed generally too high • Precipitation? difficult to assess ACCIMA Project Meeting - 16 Dec 2011

  4. Polar WRF: Other areas of development • Clouds • Deficit of clouds over the Southern Ocean • Issues with cloud radiative properties (shown for the Arctic) Total cloud fraction (Feb. 2010) Model vs observed LW at Arctic stations (July 07) AMPS/WRF CloudSat-CALIPSO Wilson et al. (2011) Cloud water/ice has no impact on LW ! ACCIMA Project Meeting - 16 Dec 2011

  5. Polar WRF: Other areas of development • Blowing snow processes • Blowing snow sublimation • Important loss term in the SMB • Important for thermodynamics and dynamics of PBL • Snow transport/redistribution Lenaerts et al. (2011) ACCIMA Project Meeting - 16 Dec 2011

  6. Polar WRF: Other areas of development • Clear-sky precipitation (“diamond dust”) • ~50% of long-term snow accumulation on the East Antarctic plateau • But few observations ACCIMA Project Meeting - 16 Dec 2011

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