measuring & modeling snow andrew g. slater. snow!

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?