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The Color Colour of Snow and its Interpretation from Imaging Spectrometry. Spectral reflectance of clean snow. Snow is a collection of scattering grains. Snow spectral reflectance and absorption coefficient of ice. Snow/cloud discrimination with Landsat. Bands 3 2 1 (red, green, blue). - PowerPoint PPT Presentation
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Spectral reflectance of clean snowSpectral reflectance of clean snow
Snow is a Snow is a collection collection of of scattering scattering grainsgrains
Snow spectral reflectance and Snow spectral reflectance and absorption coefficient of iceabsorption coefficient of ice
6
Snow/cloud discrimination with Snow/cloud discrimination with LandsatLandsat
Bands 3 2 1 (red, green, blue) Bands 5 4 2
Spectral solar irradianceSpectral solar irradiance
Net solar radiationNet solar radiation
Analyses of snow properties from Analyses of snow properties from imaging spectrometryimaging spectrometry
• Spectral albedo and conversion to broadband albedo– [Nolin & Dozier, Remote Sens. Environ.,
2000]• Fractional (subpixel) snow-covered area,
along with albedo– [Painter et al., Remote Sens. Environ., 2003]
• Liquid water in surface layer– [Green et al., Water Resour. Res., 2006]
• Absorbing impurities– [Painter et al., Appl. Environ. Microbiol.,
2001; Geophys. Res. Lett., 2007]
Conventional approach to estimating Conventional approach to estimating albedoalbedo
Satellite radiance (~5% error)
Surface reflectance (>5%)
Narrowband albedo (5-10%)
Broadband albedo (5-10%)
Estimate grain size from the1.03Estimate grain size from the1.03m absorption m absorption featurefeature
Measured vs remotely sensed grain Measured vs remotely sensed grain sizesize
500 550 600
Spectral mixture analysisSpectral mixture analysis
Spectral mixture equation, per pixel
Spectral residuals, per pixel
RMS error, per pixel
Snow-covered area in the Tokopah Snow-covered area in the Tokopah Basin (Kaweah River drainage), Sierra Basin (Kaweah River drainage), Sierra NevadaNevadaAVIRIS
05 May 1997
21 May 1997
18 June 1997
20 km
Grain size in the Tokopah Basin Grain size in the Tokopah Basin (Kaweah River drainage), Sierra (Kaweah River drainage), Sierra NevadaNevada
05 May 1997
21 May 1997
18 June 1997
20 km
Absorption by three phases of waterAbsorption by three phases of water
Wet snowWet snow
(Green et al, WRR, forthcoming)
Surface wetness with AVIRIS, Mt. Surface wetness with AVIRIS, Mt. Rainier,Rainier,14 June 199614 June 1996
AVIRIS image, 409, 1324, 2269 nm
precipitable water, 1-8
mm
liquid water, 0-5 mm
path absorption
vapor, liquid, ice
(BGR)
Progression of snow wetness Progression of snow wetness throughout morningthroughout morning
AVIRIS20 May 1996
Surfacewetness11:32 am
Surfacewetness09:54 am
70 km
N
Dust Dust and and algaealgae
Spectral reflectance of dirty snow and Spectral reflectance of dirty snow and snow with red algae (snow with red algae (Chlamydomonas Chlamydomonas nivalisnivalis))
RadiativRadiative e forcing forcing conceptconcept
24
Radiative forcing by dust in snowRadiative forcing by dust in snow
Applications: snowmelt modeling,Applications: snowmelt modeling,Marble Fork of the Kaweah RiverMarble Fork of the Kaweah River
Snow Covered Area
net radiation > 0 degree days > 0
where:
mq = Energy to water depth conversion, 0.026 cm W-1 m2 day-1
ar = Convection parameter, based on wind speed, temperature, humidity, and roughness
convection parameter, based on wind speed, humidity, and roughnessra
Melt Flux net q d rR m T a SCA
Magnitude of snowmelt: Modeled – Observed snow Magnitude of snowmelt: Modeled – Observed snow water equivalentwater equivalent
assumedalbedo
assumed w/ update
AVIRISalbedo
SWE difference, cmTokopah basin, Sierra Nevada
27
AcknowledgmentsAcknowledgments Steve Warren &
Warren Wiscombe– Model for the spectral
albedo of snow (1980)
NASA– Funding on remote
sensing of snow since 1977
• UC Santa Barbara– Great place to think
about snow and ice
Former and current students on this topic– Bert Davis, Rob
Green, Danny Marks, Anne Nolin, Tom Painter, Karl Rittger, Walter Rosenthal, Jiancheng Shi