Measurements of snow- and glacier-covered areas with single-polarization SAR

Abstract

Climatological and hydrological investigations in mountainous regions frequently require delineation of the areas covered by snow and glacial ice. Active microwave sensors can discriminate snow and glacier from other targets, are effective under all weather conditions, and have a spatial resolution compatible with the topographic variation in alpine regions. Using data acquired with the NASA AIRSAR, which operates at three frequencies and four combinations of polarization, we examine the usage of synthetic aperture radar (SAR) to map snow- and glacier-covered areas. In order to assess the available SARs that operate from satellites, we analyze single-frequency, single-polarization data, and we compare our results with images from the Landsat Thematic Mapper obtained under clear conditions only a few days after the SAR flight. Single polarization, C-band (5.3 GHz) SAR data can discriminate between areas covered by wet snow from those that are ice-free, but do not easily separate glacier ice from snow and rock. L-band SAR (1.25 GHz) data cannot discriminate between snow and glacier ice. The accuracy (74%) of SAR is high enough to justify its use as the data source in areas that are too cloud-covered to obtain reliable data from the thematic mapper.