Effect of a snow cover on microwave backscatter from sea ice

The effect of a snow cover on sea ice upon radar backscatter at microwave frequencies (
X
- and
Ku
-baud) can be important. The effect of scattering from the snow cover on the
\sigma\deg
of first-year ice is shown to be severe (5 cm of dry snow can raise
\sigma\deg
by 8 dB at 9 GHz), while that on
\sigma\deg
of multiyear ice is shown to be smaller. The low thermal conductivity of snow compared to that of sea ice effectively raises the temperature of the upper surface of the ice, resulting in higher dielectric constants for the ice, thereby modifying the backscatter both from the ice surface and from the scattering volume. The temperature effect of a 10-cm snow cover on 3-m-thick multiyear ice is to lower the
\sigma\deg
by only about 0.3 dB for air temperature of
-20\deg
C. The effect on 1-m-thick first-year ice is even less. Hence, the volume-scattering effect of snow is more important than the temperature effect. The presence of a wet snow cover can block the volume-scattering contribution of the multiyear ice. The effect of wet snow cover on first-year ice should be smaller than that Of dry, snow, because
\sigma\deg
of wet snow is lower than that of dry snow.