On the relationship between energy fluxes, dielectric properties, and microwave scattering over snow covered first‐year sea ice during the spring transition period

Abstract

In this research we investigate the seasonal nature of the co-variability in surface energy balance variables, volume dielectrics, and microwave scattering (ERS 1) of a snow-covered first-year sea ice surface during a spring transitional period. Variables required to derive the components of the energy balance and dielectric properties were measured during the Seasonal Sea Ice Monitoring and Modeling site in the Canadian Arctic Archipelago in 1992. We observed that both the energy terms and dielectric properties followed a pattern similar to the total relative scattering cross section (oø) over the seasonal transition from winter to spring. We explain this relationship through the impact of surface fluxes on dielectric and geophysical properties of the snow-covered first-year sea ice. We speculate that ice surface scattering dominated the total scattering cross section oø prior to Julian day 120 and that the snow volume contributed an increasing amount of scattering to •ø over the remainder of the season. From a multivariate statistical analysis we find that the surface temperature Ts and the net shortwave energy flux K* explained a statistically significant amount of the variation observed in the seasonal evolution of •o. An inverse relationship existed between both T s and K* relative to •,o and the influence of T s was approximately twice that of K* in explaining the observed variation in •ø. 22,401 22,402 BARBER ET AL.: ENERGY FLUXES AND MICROWAVE SCATTERING Methods Observed Variables Data used in this investigation were collected in 1992 during the Seasonal Sea Ice Monitoring and Modeling Site (SIMMS'92) experiment. SIMMS is a multiyear field experiment conducted annually in the areas adjacent to Cornwallis Island in the Canadian Arctic Archipelago [LeDrew and Barber, 1994]. Data used here were obtained from ET AL.' ENERGY FLUXES AND MICROWAVE SCATTERING Vant, M.R., R.O. Ramseier, and V. Makios, The complex-dielectric constant of sea ice at frequencies in the range 0.1 to 40 GHz, J. Appl. Phys., 49(3), 1264-1280, 1978. Wiscombe, W.J., and S.G. Warren, A model for the spectral albedo of snow, I, Pure snow, J. Atmos. Sci.

Comparison of a coupled snow thermodynamic and radiative transfer model with in situ active microwave signatures of snow-covered smooth first-year sea ice

“…SNTHERM89.rev4 does not account for brine wicking in the snow and associated salinity values. This is an important consideration, as brine-wetted snow affects C-band backscatter through both increased loss and volume scattering (Barber et al, 1994;Geldsetzer et al, 2007). As such,…”

“…This is compared to the relatively drier and cooler snow conditions in MSIB simulations driven by observed snow parameters for samples 1-3. The temperature difference is important as dielectric permittivity and loss, as a function of brine volume in the basal snow and near-surface sea ice, are the primary factors affecting C-band microwave backscatter signatures (Barber et al, 1994;Nghiem et al, 1995;Geldsetzer et al, 2009). The case A and B SNTHERM initial conditions predicted snow depths of 20 cm (A) and 27 cm (B), which compare reasonably well to the three in situ observations of 24, 26, and 32 cm (samples 1-3, respectively).…”

“…9) were applied to SNTHERM derived snow profiles for input to the MSIB: -SNTHERM 1: cases A1 and B1 were assigned typical salinity values for first-year sea ice and overlying snow (Barber et al, 1995).…”

“…Snow cover on sea ice is typically represented in physical and backscatter models as a two-or three-layer system of fine grained fresh snow or dense wind slab, overlying more coarsely grained depth hoar of lower density, and brine-covered basal snow (e.g., Crocker, 1992;Barber et al, 1995;Geldsetzer et al, 2007). However, increases in the alternation of early spring rain, snow, and melt events (Trenberth et al, 2007) can result in a more complex layering of snow.…”

Role of diurnal processes in the seasonal evolution of sea ice and its snow cover

“…In addition, the diurnal surface energy balance can affect snow grain growth, snow brine volume, and snow wetness, which in turn affect passive and active microwave signatures [see, e.g., Barber et al, 1994Barber et al, , 1995. The change in snow properties also strongly affects the surface albedo that feeds back into the surface energy balance.…”