IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India,2002
parameters one can derive the snow albedo throughout the solar
spectrum as a function of its spectral reflectances in suitable
wavelength regions where the effect of the individual
parameters is the maximum
4. CONCLUSIONS
This study demonstrates the usefulness of field based
hyperspectral reflectance studies in the 350-1800 nm
wavelength range for understanding the snowpack
characteristics in the Himalayan terrain. Results indicate that
albedo in the visible region is not affected by the grain size or
age of snow but by the amount of clay contamination. While
the effect of contamination is not significant in the near infrared
and shortwave infrared regions, grain size is the dominating
factor in these regions. Thus, the estimates of spectral
reflectances in the visible and infrared regions give the amount
of clay contamination and grain size. Spectral reflectance
reading on avalanche debris indicates that its spectral behaviour
is similar to that of a clay-contaminated snow. The region
between 450 and 900 nm is most affected by an avalanche and
a difference of 40 % in reflectance was observed between
avalanche and non-avalanche snow. Therefore, spectral
reflectances estimated in the satellite sensor bands falling in
this wavelength region, before and after the triggering of an
avalanche, will be useful in the identification and mapping of
avalanche-affected regions. This will further become an
important input in the validation and improvement of avalanche
forecast models.
Snow albedo is mainly affected by its grain size and amount of
clay contamination. Therefore, a model for snow albedo can be
developed as a function of its spectral reflectances in the visible
and infrared regions where the contamination and grain size
have independent effects. For this purpose, detailed field
measurements of grain size and amount of contamination are
needed along with spectral reflectance and albedo data. And, it
is proposed to conduct such detailed investigations in the future
for developing a snow albedo model.
ACKNOWLEDGEMENTS
The authors would like to thank Maj. Gen. (Retd.) S. S.
Sharma, KC, VSM, Director, Snow and Avalanche Study
Establishment (SASE), and Dr. A. K. S. Gopalan, Director,
Space Applications Centre (SAC), for their keen interest in this
investigation. We thank Dr. Shailesh Nayak, Group Director,
Marine and Water Resources Group, SAC, for his comments
and suggestions during the investigation.
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