Ground-based frequency-modulated continuous wave radar measurements in wet and dry snowpacks, Colorado, USA: an analysis and summary of the 2002-03 NASA CLPX data

Ground-based frequency-modulated continuous wave (FMCW) radar measurements made throughout the 2002-03 NASA Cold Lands Processes (CLPX) mission in Colorado, USA, were designed to study the major electromagnetic transitions within the alpine snowpack over a wide range of conditions, and their effect on measurements made with different active radar measurement parameters. Measurements during 2002 determined that measurements at C-, X-, and Ku-band frequencies were necessary to retrieve the most snowpack information in a wide range of conditions. Measurements at four different incidence angles indicated that the snowpack layering was still visible at 15° but that the rough surface scattering of the snow-ground interface dominated the signal above 30° incidence. Measurements during 2003 were focused on characterizing the microwave response at C-, X-, and Ku-band frequencies at four different sites with different snowpack conditions, indicating that the optimal measurement parameters vary with snowpack conditions. Measurements at different bandwidths illustrate the effect of bandwidth on vertical resolution. This ground-truth data will help interpretation of air- and space-borne active and passive microwave radar measurements that were made coincident with this study. In addition, this work may help guide future researchers when choosing FMCW radar measurement parameters, depending on the type of snowpack information their study requires.