Real permittivity of snow at 1 MHz and 0°C: Fid-Bau Portal

Real permittivity of snow at 1 MHz and 0°C

Perla, R.

AbstractThe real permittivity of 200 snow samples with wide range of density and wetness was measured in a capacitive cell at 1 MHz and at 0°C. Measurements fit three empirical functions. A good fit for the full density and wetness range is: $ϵ=Σν j ϵ j −0.43ν A ν I −50ν I ν w −100ν A ν w$ where ϵ is the relative real permittivity; j=A, I and W (air, ice and water); vj is the volume proportion of each phase; and ϵj is the dielectric constant of each phase. For low vW, the measurements fit closely a polynomial proposed earlier for ∼ 10 MHz measurements, namely: $ϵ=1+1.92ρ+0.44ρ$ ²+18.7ν w +45ν² w where ϱ is snow density (g/cm³). Measurements also fit a third function ϵ^q=∑vjϵ^qj which was used in an earlier microwav study. In agreement with microwave measurements, the empirical constant q was found to be 0.4 for wet snow in the range 0.02<vw≤0.4. The value of q was found to be higher at both the dry and very wet extremes: q=0.7 for dry snow (vw≈0); and q=0.6 for slush (0.4<vw≤1). These q values are consistent with a qualitative model of snow microstructure as a sintered ice skeleton with water inclusions that are disconnected at low vw and connect at high vw.