Measuring & Modeling Snow

1. Measuring & ModelingSnow Andrew G. Slater

2. SNOW!

3. Air to Soil Temperature Gradient Ivotuk is in the northern foothills of the Brooks Range, AK

4. Integrated Extent-Duration of Snow http://cires.colorado.edu/~aslater/NH_SNOW/

5. June Snow Cover Retreat Derksen and Brown, 2012

6. Rapid Snow Retreat in 2013

7. Snow Extent : Observations & Models

8. Trends in Snow Extent (1966-2012)

9. Nth Hemisphere Snow Mass/Depth Data

10. March SWE : Spatial Correlation (2000-2009)

11. March SWE : Spatial Correlation (2000-2009)

12. Arctic Basins Lena Yenesy Ob MacKenzie

13. 2000 – 2009 : Observations

14. 2000 – 2009 : Observations + CMIP5 Models

15. 2030 – 2039 : CMIP5 Models

16. 2060 – 2069 : CMIP5 Models

17. 2090 – 2099 : CMIP5 Models

18. Measurement Methods SNOTEL and Precipitation Gauges Snow Board Photos: A. Slater

19. Measurement Methods Sonic Snow Depth Sensor Photos: A. Slater

20. Measurement Methods Alter DFIR Nipher Wyoming Photos: NCAR

21. Measurement Methods Pyranometer and Stevenson Screen Photos: A. Slater

22. Other Data Sources CAIC Tower Berthoud Pass Snow courses & weather networks Photos: A. Slater

23. Surface Hoar Photos: A. Slater

24. Depth Hoar Photo: http://www.avalanche.org/

25. Depth Hoar Formation • Driven by vapor density gradient, but temperature is a good proxy • Large temp gradient, high temperatures & large pores = big crystals • ~10°C/m is the critical gradient

26. Fresh Snow Density Grant & Rhea, 1974 Colorado

27. Snow Crystal Formation Based on Magono & Lee, 1966 (Observations) Nakaya, 1945 (Lab Experiments)

28. North Slope Alaska, April 2009

29. Constructive Metamorphism Snow stratigraphy (right) at site KD-7 (Yamba Lake). The color representation of the NIR image of the left side of the snowpit indicates the relative grain size (yellow and red = largest; purple and blue = smallest). Sturm et al., 2008

30. 2011

31. 2012

32. 2013

35. * * * * * Manabe, 1969 – 1970’s Radiation Albedo = 0.70 Snowfall Air to ground temperature gradient Snow Mass/Depth Accumulation Ablation Time

36. Wind * * * * * Climate Model(1980’s) Radiation Turbulentfluxes Albedo ~ Age Snowfall Sublimation Evaporation Snow Mass/Depth Runoff Ground heat flux Metamorphism = f (mass) Accumulation Ablation Time

37. Wind * * * * * Land Surface Model (1990’s) Radiation Turbulentfluxes Albedo ~ Tsnow Snowfall Sublimation Evaporation Snow Mass/Depth settling compaction compaction Runoff Metamorphism = f (age) Accumulation Ablation Time Ground heat flux

38. Wind * ‘ ‘ * ‘ ‘ * * ‘ * More Sophisticated Snow Model (2000’s) Radiation Turbulentfluxes Heat due to rain Albedo ~ Age ~ Sun angle ~ Cloud Snowfall Sublimation Evaporation Rain Snow Mass/Depth ice layer wet metamorphism settling settling compaction compaction Runoff Metamorphism = f (mass, temperature, age) Accumulation Ablation Time Ground heat flux

39. Instrument Pass Bands & Spectral Reflectences Image Courtesy: Bruce Raup, NSIDC

40. Any Questions Before I Leave?