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Timothy E. Link - University of Idaho John Pomeroy - University of Saskatchewan

A Sensitivity Study of Radiant Energy During Snowmelt in Small Canopy Gaps: The quest for the radiative minima and more. Timothy E. Link - University of Idaho John Pomeroy - University of Saskatchewan Robert Lawler - U.S. Forest Service Chad Ellis - Silvatech Consulting Ltd.

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Timothy E. Link - University of Idaho John Pomeroy - University of Saskatchewan

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  1. A Sensitivity Study of Radiant Energy During Snowmelt inSmall Canopy Gaps: The quest for the radiative minima and more... • Timothy E. Link - University of Idaho • John Pomeroy - University of Saskatchewan • Robert Lawler - U.S. Forest Service • Chad Ellis - Silvatech Consulting Ltd. • Danny Marks – USDA ARS • Richard Essery - University of Edinburgh

  2. Outline • Motivation & background • Radiation in forest gaps • Measurements • Modeling • Scaling up... • Future directions and challenges

  3. Motivation • Snow is a major water source • 50% - 90% in western U. S. watersheds • Declining in many areas • Improve melt prediction in complex terrain • Can forest managementconserve snow? • Gap thinning • Homogeneous thinning

  4. Snow in Forests Shortwave Dominated Longwave Dominated

  5. Canopy Effects Summary • ↓ SWE • ↓ Shortwave Radiation • ↑ Longwave Radiation • ↓ Wind Speed In forests, relative to open areas... ...and hence: Loss of forest canopy should: 1. Increase snow !! 2. Accelerate melt !!! Not always so!!!

  6. High Noon in November Canopy Gaps...a.k.a “cold holes”(Berry & Rothwell, 1992) • are “open”, and so... • - Accumulate more snow • but... • - Are dark and cold Wolf Creek Experimental Basin, Yukon Territory

  7. Some history... Church. 1933. Geog. Rev.

  8. More history... Golding & Swanson. 1978. Can. J. For. Res.

  9. More history... Golding & Swanson. 1986. Wat. Resour. Res.

  10. More history... Berry & Rothwell. 1992. Can. J. For. Res.

  11. and so the question is... • How does radiation vary as function of position, gap size, season, and latitude ? • Optimal density and pattern to minimize radiation to snow?

  12. Methods • Radiation measurements • Physically-based models • Sensitivity experiments

  13. Radiation Measurements measuring sunshine in a campground in winter...

  14. Simple Model PerformanceShortwave Radiation Text Lawler & Link, Hyd. Proc., 2011

  15. Model Performance:Longwave Radiation Lawler & Link, Hyd. Proc., 2011

  16. Simulated Radiation Regimes Gap Position, Size, and seaSON

  17. Gap Radiation Regimes ~47° N latitude February 1 Lawler & Link, Hyd. Proc., 2011

  18. Proportion Gap Radiation RegimesFebruary 1, ~47° N latitude Lawler & Link, Hyd. Proc., 2011

  19. Proportion Gap Radiation RegimesMay 1, ~47° N latitude Lawler & Link, Hyd. Proc., 2011

  20. Snow Depth Trends ~47° N latitude

  21. Simulated Radiation Regimes: Another View… Gap Size, seaSON, And Latitude

  22. Gap Radiative RegimesInstantaneous, Gap Center

  23. Data AnalysisDaily Incoming Radiation

  24. Data AnalysisDaily Incoming Radiation

  25. Data AnalysisDaily Incoming Radiation shortwave-dominated longwave-dominated

  26. Data AnalysisDaily Incoming Radiation

  27. Link et al., in prep.

  28. Link et al., in prep.

  29. Gaps on SlopesNorth and South Ellis et al., WRR, in press

  30. Gaps on SlopesEast and West Ellis et al., WRR, in press

  31. Conclusions(so far!) Radiative minima occur in gaps • Optimal size: 1-2 H at ~45° latitude • Snow can be retained on the landscape • Melt can be desynchronized on slopes • Canopy gap microclimates are distinct Implications: • Water resource prediction & enhancement • Climate change adaptation • Monitoring site assessment • Fire hazard risk reduction • Avalanche initiation • Vegetation regeneration

  32. Cedar River Watershed Washington, USA Marmot Creek Research Basin Alberta, Canada The Marmot Creek Legacy Cedar River Watershed Washington, USA

  33. Future Directions:Discrete Tree Model Images courtesy of Dr. Richard Essery

  34. Future Directions - How does radiation vary as function of canopy density, pattern, slope, and ... - Optimal density and pattern to minimize radiation to snow?

  35. Seasonal effects ? Productive melt conditions Comprehensive snow energetics ? Climatological variability ? Spatial Temporal (Intra and inter-annual) Depositional effects ? Sublimation vs. meltwater drip Deportment of infiltrated water? ~4H gap ~1H gap The Quest for More…

  36. ThankYou ! Questions ?

  37. Approach: Modeling Seyednasrollah et al., In review. JGR - Atmospheres.

  38. Example Results:Discrete Tree Model Essery et al., 2007. J. Hydromet.

  39. In Summary... • Forests can have higher radiation than open • High latitudes, mid-winter, north slopes • Gaps can have lowest radiation amounts • During melt !! • Distinct at high latitudes • North slopes are likehigh latitudes

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