Abstract
Changes in snowpack associated with climatic warming has drastic impacts on surface energy balance in the cryosphere. Yet, traditional monitoring techniques, such as punctual measurements in the field, do not cover the full snowpack spatial and temporal variability, which hampers efforts to upscale measurements to the global scale. This variability is one of the primary constraints in model development. In terms of spatial resolution, active microwaves (synthetic aperture radar—SAR) can address the issue and outperform methods based on passive microwaves. Thus, high spatial resolution monitoring of snow depth (SD) would allow for better parameterization of local processes that drive the spatial variability of snow. The overall objective of this study is to evaluate the potential of the TerraSAR-X (TSX) SAR sensor and the wave co-polar phase difference (CPD) method for characterizing snow cover at high spatial resolution. Consequently, we first (1) quantified the spatio-temporal variability of the geophysical properties of the snowpack in an Arctic catchment, we then (2) studied the links between snow properties and CPD, considering ground vegetation. Snow depth (SD) could be extracted using the CPD when certain conditions are met. A high incidence angle (> 30°) with a high Topographic Wetness Index (TWI) (> 7.0) showed correlation between SD and CPD (R-squared up to 0.72). Further, future work should address a threshold of sensitivity to TWI and incidence angle to map snow depth in such environments and assess the potential of using interpolation tools to fill in gaps in SD information on drier vegetation types.
Highlights
Snow cover is a key component of the cryosphere which plays an essential role for ecological processes and hydrological dynamics
The overall objective of this study is to evaluate the potential of the TerraSAR-X (TSX) SAR sensor and the wave co-polar phase 20 difference (CPD) method for characterizing snow cover at high spatial resolution
Highest depth hoar fraction (DHF) along the transect were found on the west side of the transect and on the slopes with an average of 0.76 while an average of 0.39 was observed on the east side of the catchment
Summary
Snow cover is a key component of the cryosphere which plays an essential role for ecological processes and hydrological dynamics. The objective of this paper is to evaluate the potential of polarimetric method co-polar phase difference (CPD) produced with the X-band satellite TerraSAR-X to retrieve SD from an arctic snowpack where vegetation is highly variable This general objective requires a complete characterization of the snowpack from field data to fully understand the sensitivity of CPD to various snow characteristics. Given the dry nature of the arctic snowpack, the main source of backscattering should occur at the snow-ground interface for frequencies in X-band (λ = 3.1 cm) such as used in this study or below as dry snow can be considered as a homogeneous, “non-scattering” and non-absorbing volume (Leinss et al, 2014) This said, inhomogeneous layers such as ice layers, melt/freeze crust and any strong vertical change in dielectric properties (i.e. density, wetness) can affect the signal
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