Sub-Grid Scale Variability of Snow Grain Size and Snow Wetness in the ABoVE Region

Abstract:

In this project we track the evolution of snow grain size and snow wetness in the top layers of the snowpack in the ABOVE domain at very high spatial resolution (e.g. 30m) toward understanding the temporal evolution of the subgrid-scale variability and its scaling behavior. We use Sentinel 1 C-band SAR dual polarization VV and VH channels and Normalized Difference Snow Index (NDSI) from LandSat to detect and identify wet snow pixels in the study region. The 6SV-1 atmospheric correction model to determine surface reflectance values from the Landsat data, and three different snow grain size retrieval models were applied to the surface reflectance values in visible and near infrared channels to estimate grain sizes at 30 m resolution. The high resolution snow grain maps were upscaled to ~ 450 m for comparison against the MODIS snow grain size product (MODSCAG). Snowfall events were identified from reanalysis and a history of snowpack evolution vis-à-vis regional weather was developed to guide the interpretation of time-varying spatial scaling behavior in snow grain size and areal fraction of wet snow. The scaling analysis in the winter-spring transition and into the ablation season is further examined in the context of landform features, vegetation cover and soil type.