Post on 13-Jan-2016
Measuring & ModelingSnow
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 25km EASE Grid 2000-2007 Passive Microwave Armstrong & Brodzik
GlobSno 25km EASE Grid 2000-2009 Station data + Microwave Takala et al, 2011
ERAI 0.75 x 0.75 Deg 2000-2009 Reanalysis, with depth analysis Dee et al.
JRA 1.125 x 1.125 Deg 2000-2009 Reanalysis, with depth analysis Onagi et al.
CFSRR 0.33 x 0.33 Deg 2000-2009 Reanalysis, with depth analysis Saha et al
NARR 32km (NCEP 221) 2000-2009 Reanalysis, with depth analysis Messinger et al
ASR 30km WRF grid 2000-2009 Reanalysis, with depth analysis Bromwich et al.
MERRA 0.5 x 0.666 Deg 2000-2009 Reanalysis, forecast Reinecker et al.
CIRES 2.5 x 2.5 Degrees 2000-2009 Reanalysis, forecast Compo et al.
CMC ~24km IMS grid 2000-2009 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 BasinsLena
MacKenzie
Ob
Yenesy
2000 – 2009 : Observations
2000 – 2009 : Observations + CMIP5 Models
2030 – 2039 : CMIP5 Models
2060 – 2069 : CMIP5 Models
2090 – 2099 : CMIP5 Models
Measurement Methods
Photos: A. Slater
SNOTEL and Precipitation Gauges Snow Board
Measurement Methods
Photos: A. Slater
Sonic Snow Depth Sensor
Measurement MethodsAlter
Wyoming
DFIR
Nipher
Photos: NCAR
Measurement Methods
Photos: A. Slater
Pyranometer and Stevenson Screen
Other Data Sources
CAIC TowerBerthoud Pass
Photos: A. Slater
Snow courses & weather networks
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, 1974Colorado
Snow Crystal Formation
Nakaya, 1945 (Lab Experiments)
Based on Magono & Lee, 1966 (Observations)
SectorPlates
Very Thick Plates
Hollow
SolidPrisms
SolidPrisms
Cups
-10 -20 -30 -40TEMPERATURE (oC)
0
Prisms
0
10
20
30
40
50
60
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
Accumulation Ablation
Time
Sn
ow M
ass/
Dep
th
Snowfall
****
*
Albedo = 0.70
Air to groundtemperature gradient
Radiation
Climate Model (1980’s)
Metamorphism = f (mass)Accumulation Ablation
Time
Sn
ow M
ass/
Dep
th
Snowfall SublimationEvaporation
Runoff
****
*
WindAlbedo ~ Age
Ground heat flux
Radiation Turbulent fluxes
Land Surface Model (1990’s)
Metamorphism = f (age)Accumulation Ablation
Time
Sn
ow M
ass/
Dep
th
Snowfall SublimationEvaporation
Runoffsettling compaction
compaction
****
*
WindAlbedo ~ Tsnow
Turbulent fluxesRadiation
Ground heat flux
More Sophisticated Snow Model (2000’s)
Metamorphism = f (mass, temperature, age)Accumulation Ablation
Time
Sn
ow M
ass/
Dep
thTurbulent fluxesRadiation Heat due to rain
Ground heat flux
Snowfall SublimationEvaporation
Rain
ice layer
Runoffsettling
settling
compactioncompaction
wet metamorphism
****
*
Wind
‘‘‘
‘‘
Albedo ~ Age ~ Sun angle ~ Cloud
Instrument Pass Bands & Spectral Reflectences
Image Courtesy: Bruce Raup, NSIDC
Any Questions Before I Leave?