Potential of Operational High Spatial Resolution Near-Infrared Remote Sensing Instruments for Snow Surface Type Mapping

Snow changes its morphology permanently from the moment a snow flake touches the ground. Under the influence of meteorological factors such as temperature, humidity, and wind, snow grains form complex structures of ice bonds enclosing variable portions of air. The characteristics of such structures are important for the formation of snow avalanches. Certain snow types such as surface hoar, ice crusts, or windblown snow play a major role in the formation of weak layers and slabs, which are precondition for dangerous slab avalanches. The reflection properties of snow depend on the optical equivalent grain size of the ice particles that constitute the snow cover. High spatial resolution remote sensing instruments with near-infrared (0.7-1.4 μm) bands are able to detect such differences in the optical reflection of snow. We use normalized difference index band ratios from a spaceborne and an airborne remote sensing instrument to distinguish and map different snow-surface types in the neighborhood of Davos, Switzerland, enabling a valuable visualization of the spatial variability of the snow surface.