A Hyperspectral Method for Remotely Sensing the Grain Size of Snow

We have developed a robust, accurate inversion technique for estimating the grain size in a snowpackʹs surface layer from imaging spectrometer data. Using a radiative transfer model, the method relates an ice absorption feature, centered at λ=1.03 μm, to the optically equivalent snow grain size. Because the interpretation is based on the area—not depth—of the absorption feature scaled to absolute reflectance, the method is insensitive to instrument noise and does not require a topographic correction. We tested the method using Airborne Visible/Infrared Imaging Spectrometer data over the eastern Sierra Nevada, California, and we validated it with a combination of ground-based spectrometer data and grain size measurements.