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Measuring & Modeling Snow
Andrew G. Slater
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SNOW!
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Air to Soil Temperature Gradient
Ivotuk is in the northern foothills of the Brooks Range, AK
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Integrated Extent-Duration of Snow
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June Snow Cover Retreat
Derksen and Brown, 2012
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Rapid Snow Retreat in 2013
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Snow Extent : Observations & Models
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Trends in Snow Extent (1966-2012)
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Nth Hemisphere Snow Mass/Depth Data
Product Native Resolution Period Product Type Reference AMSR-E 25km EASE Grid Passive Microwave Tedesco et al, 2004 SSMI Armstrong & Brodzik GlobSno Station data + Microwave Takala et al, 2011 ERAI 0.75 x 0.75 Deg Reanalysis, with depth analysis Dee et al. JRA 1.125 x Deg Onagi et al. CFSRR 0.33 x 0.33 Deg Saha et al NARR 32km (NCEP 221) Messinger et al ASR 30km WRF grid Bromwich et al. MERRA 0.5 x Deg Reanalysis, forecast Reinecker et al. CIRES 2.5 x 2.5 Degrees Compo et al. CMC ~24km IMS grid Station interpolation/analysis Ross Brown ETAC 1.0 x 1.0 degree Pre-1988 Station interpolation Foster & Davey GRACE Big (ask Sean) Gravity anomaly Sean Swenson
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March SWE : Spatial Correlation (2000-2009)
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March SWE : Spatial Correlation (2000-2009)
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Arctic Basins Lena Yenesy Ob MacKenzie
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2000 – 2009 : Observations
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2000 – 2009 : Observations + CMIP5 Models
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2030 – 2039 : CMIP5 Models
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2060 – 2069 : CMIP5 Models
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2090 – 2099 : CMIP5 Models
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Measurement Methods SNOTEL and Precipitation Gauges Snow Board
Photos: A. Slater
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Measurement Methods Sonic Snow Depth Sensor Photos: A. Slater
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Measurement Methods Alter DFIR Nipher Wyoming Photos: NCAR
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Measurement Methods Pyranometer and Stevenson Screen Photos: A. Slater
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Other Data Sources Snow courses & weather networks CAIC Tower
Berthoud Pass Snow courses & weather networks Photos: A. Slater
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Surface Hoar Photos: A. Slater
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Depth Hoar Photo:
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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
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Fresh Snow Density Grant & Rhea, 1974 Colorado
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Snow Crystal Formation
Based on Magono & Lee, 1966 (Observations) Nakaya, 1945 (Lab Experiments)
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North Slope Alaska, April 2009
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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
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2011
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2012
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2013
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Manabe, 1969 – 1970’s * Snow Mass/Depth Time Radiation Albedo = 0.70
Snowfall * Air to ground temperature gradient Snow Mass/Depth Accumulation Ablation Time
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Climate Model (1980’s) * Snow Mass/Depth Time Radiation
Turbulent fluxes Albedo ~ Age Wind Snowfall Sublimation Evaporation * Snow Mass/Depth Runoff Ground heat flux Metamorphism = f (mass) Accumulation Ablation Time
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Land Surface Model (1990’s)
Radiation Turbulent fluxes Albedo ~ Tsnow Wind Snowfall Sublimation Evaporation * Snow Mass/Depth settling compaction compaction Runoff Metamorphism = f (age) Accumulation Ablation Time Ground heat flux
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More Sophisticated Snow Model (2000’s)
Radiation Turbulent fluxes Heat due to rain Albedo ~ Age ~ Sun angle ~ Cloud Wind Snowfall Sublimation Evaporation Rain * ‘ Snow Mass/Depth ice layer settling wet metamorphism settling compaction compaction Runoff Metamorphism = f (mass, temperature, age) Accumulation Ablation Time Ground heat flux
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Instrument Pass Bands & Spectral Reflectences
Image Courtesy: Bruce Raup, NSIDC
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Any Questions Before I Leave?
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