Presentations text content in 1 Remote sensing of snow in visible and near-infrared wavel
Slide1
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Remote sensing of snow in visible and near-infrared wavelengths
Jeff Dozier – UCSB
NASA Snow Remote Sensing Workshop
Boulder, August 2013
Slide2Different concepts in different parts of spectrum
Visible, near-infrared, and infraredIndependent scatteringWeak polarizationScalar radiative transferPenetration near surface only~0.3 m in blue, few mm in NIR and IRSmall dielectric contrast between ice and water
Microwave and millimeter waveExtinction per unit volumePolarized signalVector radiative transferLarge penetration in dry snow, many mEffects of microstructure and stratigraphySmall penetration in wet snowLarge dielectric contrast between ice and water
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Slide3Optical properties of ice & water — visible and near-infrared wavelengths
wavelength,
m
(Warren,
Applied Optics,
1982)
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Slide4N=n+ik, Index of refraction (complex)
i
r
I
0
I
dx
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Slide5Basic scattering properties of a single grain
Mie theory, based on
N
and
x=2
r/
— single-scattering albedo
g —
asymmetry parameter
Q
ext
—
extinction efficiency
Slide6Snow is a collection of scattering grains
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Slide7Snow spectral reflectance and absorption coefficient of ice
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Slide8Spectra with 7 MODIS “land” bands (500m resolution, global daily coverage)
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Slide9Landsat Thematic Mapper (TM, on Landsats 4,5,7)
30 m spatial resolution185 km FOV16 day repeat passLandsat 8 launched in February 2013
Slide1010
Benefit of shortwave-infrared
Landsat snow-cloud discrimination
Bands 3 2 1
(visible)
Bands 5 4 2 (
V,nIR,swIR
)
Slide11MODIS: similar bands, wider swath (2300 km), bigger pixels (500 m), daily coverage
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Slide12Snow cover from MODIS
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Slide13Comparison of MODIS (500m) and Landsat (30m) fSCA
32 scenes with coincident MODIS and Landsat images
Average
RMSE = 7.8%Range from 2% to 12%
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Slide14Cloudy, 20%-80% depending on where/when
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1 Remote sensing of snow in visible and near-infrared wavel
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