Lower frequency microwave radar observations can help to measure the proper
ties of snow cover on land by providing information about the soil-snow bou
ndary condition. In this theoretical study, we examine the sensitivities of
microwave radar measurements to soil and snow characteristics, and we comp
are a simple model with previously published data. Depending on the surface
roughness, copolarized ratios or single polarization time ratios of radar
backscattering may be affected only by the incidence angle and the dielectr
ic contrast at the soil-snow boundary. These measurements can reduce the nu
mber of unknowns in any corresponding higher-frequency observations that ar
e also affected by the lower boundary condition. The copolarized ratio is s
ensitive, first of all, to the snow density, which offers the possibility o
f measuring this parameter directly if a separate measurement of the soil t
emperature from a passive microwave system is also available. The thermal i
nsulation provided by snow cover can have a powerful effect on the soil-sno
w boundary by altering the soil temperature and therefore changing the diel
ectric contrast. Because the microwave response of snow cover is so sensiti
ve to the conditions of the underlying frozen soil, it is important for fut
ure ground truth campaigns that measure snow conditions to also collect dat
a on the temperature, water content, and texture of the soil.