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Remote sensing of snow in visible and near-infrared wavelengths

Remote sensing of snow in visible and near-infrared wavelengths. Jeff Dozier – UCSB NASA Snow Remote Sensing Workshop Boulder, August 2013. Visible, near-infrared, and infrared Independent scattering Weak polarization Scalar radiative transfer Penetration near surface only

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Remote sensing of snow in visible and near-infrared wavelengths

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  1. Remote sensing of snow in visible and near-infrared wavelengths Jeff Dozier – UCSBNASA Snow Remote Sensing WorkshopBoulder, August 2013

  2. Visible, near-infrared, and infrared Independent scattering Weak polarization Scalar radiative transfer Penetration near surface only ~0.3 m in blue, few mm in NIR and IR Small dielectric contrast between ice and water Microwave and millimeter wave Extinction per unit volume Polarized signal Vector radiative transfer Large penetration in dry snow, many m Effects of microstructure and stratigraphy Small penetration in wet snow Large dielectric contrast between ice and water Different concepts in different parts of spectrum

  3. Optical properties of ice & water — visible and near-infrared wavelengths (Warren, Applied Optics, 1982) wavelength, m

  4. N=n+ik, Index of refraction (complex) i r dx I0 I

  5. Snow is a collection of scattering grains

  6. Snow spectral reflectance and absorption coefficient of ice

  7. Spectra with 7 MODIS “land” bands (500m resolution, global daily coverage)

  8. Landsat Thematic Mapper (TM, on Landsats 4,5,7) • 30 m spatial resolution • 185 km FOV • 16 day repeat pass • Landsat 8 launched in February 2013

  9. Bands 3 2 1(visible) Bands 5 4 2 (V,nIR,swIR) Landsat snow-cloud discrimination Benefit of shortwave-infrared

  10. MODIS: similar bands, wider swath (2300 km), bigger pixels (500 m), daily coverage

  11. Snow cover from MODIS

  12. Comparison of MODIS (500m) and Landsat (30m) fSCA 32 scenes with coincident MODIS and Landsat images Average RMSE = 7.8% Range from 2% to 12%

  13. Cloudy, 20%-80% depending on where/when

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