Of special interest within the field of avalanche research and avalanche warning are
properties related to snow grain type and snow grain size at the surface. In continental and intermountain
avalanche climates weak layers or interfaces are the main cause of avalanches. Knowledge
about such weak layers helps to increase the precision of avalanche forecasting. Some of these potential
weak layers form on the snow surface and are preserved until burial.
Optical satellite sensors measure reflected sunlight at different wavelengths. The near-infrared region
is sensitive to the optical grain size of the snow. Due to the distinct size and shape characteristics of
potential weak layers such as, for example, surface hoar, their reflectance is quite different from new
snow in general. If the weather permits optical observations it should, therefore, be possible to detect
such layers by remote sensing.
We present the results of a pilot study where in situ measured surface snow grain characteristics are
compared to snow grain characteristics as derived from multispectral data from the MODIS satellite
sensor. The pilot study showed that parallel in situ snow measurements and snow analyses exploiting
data from MODIS are possible for the selected test sites in Norway. The study aims at establishing a
relationship between the satellite-observed snow grain size index (SGS) variable and the snow grain
size and shape as measured in the field. Based on satellite and in situ data measured over several
years, we intend to establish a snow grain evolution model. The model will be used as an input to the
avalanche forecasting model