1. Space-Time Series of MODIS Snow Cover Products
Jeff Dozier, James E Frew, Thomas H Painter

2. Topics Spectral reflectance of snow and its variability
Implications for energy balance of snowpack
Remote sensing of snow-covered area and albedo
Fractional (subpixel) snow cover and grain size from MODIS, every day
Time series corrections for clouds, viewing geometry, and other noise
Available for use by others for hydrologic models

3. Seasonal solar radiation, Mammoth Mountain

4. Snow is a collection of scattering grains

5. Snow spectral reflectance and absorption coefficient of ice

6. Spectra with MODIS “land” bands

7. MODIS image of Sierra Nevada
EOS Terra MODIS
07 March 2004
MOD09 Surface Reflectance

8. Snow covered-area and grain size – Sierra Nevada (the MODSCAG model)

9. Spectral mixture analysis, generalized
Spectral mixture equation, per pixel
Spectral residuals, per pixel
RMS error, per pixel
MODSCAG spectrally mixes with range of snow endmembers and chooses the result with the least RMS error for that pixel

10. Based on work with AVIRIS: Snow-covered area in the Tokopah Basin (Kaweah River drainage)
21 May 1997
05 May 1997
18 June 1997
20 km

11. Grain size in the Tokopah Basin (Kaweah River drainage)
21 May 1997
05 May 1997
18 June 1997
20 km

12. Analysis of MODIS data for a single day

13. But some days are cloudy

14. Noisy variability caused by look angle, small clouds, vegetation, topography
detail
Vegetation causes differences in view angle

15. Variability of snow cover and grain size at a pixel

16. Need to interpolate and smooth to fill the space-time cube
Raw snow cover
Interpolated snow cover

17. Time series, Tuolumne basin, Oct 2004 – July 2005

18. Comparison of fractional snow cover with “binary” (pixel snow-covered when f ≥ 0.5)

19. Products available from the Snow Server http://www.snow.ucsb.edu
Fractional snow-covered area, grain size (and contaminants) from daily MODIS images
Quality flags for cloud cover, highly oblique viewing
Fractional coverage of other endmembers
Best estimate of snow-covered area and broadband albedo on that date
Extrapolating from previous values to that date and smoothing
End-of-season reanalysis of daily snow-covered area and broadband albedo
Interpolation, smoothing, comparison with in situ snow pillow data

20. Delivery options (need your opinion)