Measuring & Modeling Snow Andrew G. Slater
SNOW!
Air to Soil Temperature Gradient Ivotuk is in the northern foothills of the Brooks Range, AK
Integrated Extent-Duration of Snow http://cires.colorado.edu/~aslater/NH_SNOW/
June Snow Cover Retreat Derksen and Brown, 2012
Rapid Snow Retreat in 2013
Snow Extent : Observations & Models
Trends in Snow Extent (1966-2012)
Nth Hemisphere Snow Mass/Depth Data Product Native Resolution Period Product Type Reference AMSR-E 25km EASE Grid 2002-2009 Passive Microwave Tedesco et al, 2004 SSMI 2000-2007 Armstrong & Brodzik GlobSno 2000-2009 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 1.125 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 0.666 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) 2002-2008 Gravity anomaly Sean Swenson
March SWE : Spatial Correlation (2000-2009)
March SWE : Spatial Correlation (2000-2009)
Arctic Basins Lena Yenesy Ob MacKenzie
2000 – 2009 : Observations
2000 – 2009 : Observations + CMIP5 Models
2030 – 2039 : CMIP5 Models
2060 – 2069 : CMIP5 Models
2090 – 2099 : CMIP5 Models
Measurement Methods SNOTEL and Precipitation Gauges Snow Board Photos: A. Slater
Measurement Methods Sonic Snow Depth Sensor Photos: A. Slater
Measurement Methods Alter DFIR Nipher Wyoming Photos: NCAR
Measurement Methods Pyranometer and Stevenson Screen Photos: A. Slater
Other Data Sources Snow courses & weather networks CAIC Tower Berthoud Pass Snow courses & weather networks Photos: A. Slater
Surface Hoar Photos: A. Slater
Depth Hoar Photo: http://www.avalanche.org/
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
Fresh Snow Density Grant & Rhea, 1974 Colorado
Snow Crystal Formation Based on Magono & Lee, 1966 (Observations) Nakaya, 1945 (Lab Experiments)
North Slope Alaska, April 2009
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
2011
2012
2013
Manabe, 1969 – 1970’s * Snow Mass/Depth Time Radiation Albedo = 0.70 Snowfall * Air to ground temperature gradient Snow Mass/Depth Accumulation Ablation Time
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
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
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
Instrument Pass Bands & Spectral Reflectences Image Courtesy: Bruce Raup, NSIDC
Any Questions Before I Leave?