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J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter

Enhancement of the single layer snow model in TERRA: Global numerical experiments. J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter. Computing the snow density Snow depth, snow heat conductivity Scalar roughness length over snow Global numerical experiments. Outline.

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J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter

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  1. Enhancement of the single layer snow model in TERRA: Global numerical experiments J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter

  2. Computing the snow density Snow depth, snow heat conductivity Scalar roughness length over snow Global numerical experiments Outline

  3. Single layer snow model

  4. Routine Snow depth, heat conductivity, snow density:

  5. Snow density: Experiment

  6. Case study: Snow storm „Daisy“ January 2010 PEPS 2010010812 Pictures from Tagesschau.de

  7. Experiment: Daisy 2010010800 96h GME

  8. Experiment: Daisy 2010010800 96h GME

  9. Experiment: Daisy 2010010800 96h GME

  10. Fresh snow

  11. Snow depth

  12. Snow density

  13. ROUTI - EXP

  14. ROUTI - EXP

  15. Scalar roughness length over snow Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment http://www.crrel.usace.army.mil/sid/SeaIceDynamics/SHEBA.htm http://www.esrl.noaa.gov/psd/psd3/arctic/sheba/ Baltimore site with ridge in background. The main camp for the SHEBA project was based around the CCG Ice Breaker DeGroseilliers

  16. GME Exp Scalar roughness length over snow • Experiment: additional variable for z0t: gz0s: • Minimum: zT= 1.E-4 m Andreas et al., 2004 Ice station Weddel

  17. Scalar roughness length over snow: SURFEX Example: SWE=40mm, SWEmin=10mm beta_s=0.408s^2/m z0=10cm f_s=0.09 z0t=9.1cm

  18. Experiment 7667 • Computing the adapted snow density with implications for snow depth, snow heat conductivity • Scalar roughness length over snow • Winter 2009/2010; first month: December 2009

  19. Verification T850 BIAS

  20. Verification G500 ANOC

  21. Verification

  22. Global Verification EXP 7667 SNOW 02.12.2009-31.12.2009 00 UTC i192f T_2M TDD_2M P_SURF SK: 2.37 SK: -0.57 SK: -0.39 Europe SK: -4.21 SK: -1.88 SK: -0.27 East Sibiria SK: -4.03 North-West Sibiria SK: 0.45 SK: -3.82 SK: -4.74 South-West Sibiria SK: -2.74 SK: -0.14 SK: 1.32 SK: 0.22 SK: 0.69 North America

  23. Conclusions • Routine snow density formulation leads to underestimation of snow depth, overestimation of snow heat conductivity • Revised formulation could alleviate to a certain degree this problem • Introduction of scalar roughness length over snow accounts for decrease in roughness length with increasing grid point snow amount • Verification of EXP7667 for December 2009 shows positive impact of model changes for regions with warm 2m-temperature bias

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