Ku-, X- and C-band measured and modeled microwave backscatter from a highly saline snow cover on first-year sea ice

Ku-, X- and C-Band Microwave Backscatter Indices from Saline Snow Covers on Arctic First-Year Sea Ice

“…The Ku-(17.25 GHz) and X-band (9.65 GHz) UW-Scat scatterometer system operated concurrently with the C-band (5.52 GHz) scatterometer, with three overlapping replicate scans, completed within an hour. Detailed description of both scatterometer system specifications can be found under Table 1 in [14]; and details of calibration process, near-field correction and error determination documented in [21] (for Ku-and X-bands) and [22] (for C-band). In a 60° azimuth scan range, the scatterometer scan lines are averaged, as a function of system geometry and antenna beam-width, in order to obtain a minimum of 10 (Ku-and C-bands) and 15 (X-band) independent samples per scan line.…”

“…The UW-Scat system acquired microwave backscatter at θ inc between 21 • and 81 • at 2 • increments, while the C-band scatterometer system acquired data between 15 • and 75 • at 3 • increments. A rough illustration of scatterometer acquisition method can be found in Figure 3b in [14]. Only the co-polarized backscatter coefficients (σ 0 VV and σ 0 HH ) are used within our current study context, as the magnitude of cross-polarized σ 0 HV is very low, owing to the high noise level (−50 dBm 2 for Ku-and X-band and −36 dBm 2 for C-band), restricting the usability of scatterometer measurements for upscaling to recently operating space-borne dual-polarized SAR systems.…”

“…However, it has to be noted that stochastic variability in snow thermophysical properties from a single snow cover from different snow pits located within small spatial scales may exist [16]. This study also assumes the air/snow interface and within-snow interfaces to be radar smooth [14]. This is important to be noted as the both the scatterometer systems are not co-located and scan a relatively wide area at 60 • azimuth scan range; and therefore the snow covered area covering the scatterometer scan area is assumed to be isotropic in nature.…”

“…Active microwave remote sensing techniques employing space-borne scatterometry and Synthetic Aperture Radar (SAR) have proven to be effective tools to characterize the electrical and thermodynamic state of snow covered FYI, where snow cover plays a critical role in microwave interactions (propagation and scattering) within the snow/sea ice system [8][9][10][11][12][13][14]. With changes in snow thickness and its associated thermophysical properties such as snow temperature, snow salinity, snow density and snow grain size (grain radius or specific surface area) on FYI, microwaves exhibit characteristic variations within different snow cover types on FYI [15,16].…”

“…Plot-scale studies are crucial to understand detailed high-resolution behavior of various thermophysical processes from different snow cover types, which dictate the microwave backscattering behavior at multiple frequencies. Using surface-based and air-borne multi-frequency and multi-polarization measurements, a significant amount of research has investigated microwave backscatter sensitivity to plot-scale changes in snow thermophysical properties (e.g., [14,[17][18][19][20]). However, no previous studies have explored the potential of characterizing these plot-scale polarization-dependent multi-frequency microwave backscatter diversity from different snow cover types on Arctic FYI.…”