Sentinel-1 SAR Wet snow maps for Southern Norway, 2016-2020

Sentinel-1 Synthetic Aperture Radar data have been processed to produce daily maps of wet snow for Southern Norway for the period 2016-2020. This study makes use of the Interferometric-wide (IW) swath mode which has a swath width of 250 km and nominal pixel spacing of 10 m. We use the S1 IW ground-range detected (GRD) product with co- (“VV”) and cross- (“VH”) polarizations, and pixels are aggregated to a spacing of 100 m to reduce noise. The SAR backscatter images have been processed to produce daily wet snow maps using the Nagler and Rott (2016) approach which utilises backscatter from both VV and VH polarizations and a weighting to the contributions is applied to represent an incident angle correction. SAR image pixels are classified by applying a threshold to the difference between the SAR backscatter and its reference value. These reference values are produced for each sensor and geometry by calculating the average radar backscatter per pixel, based on data acquired in the period November 1st - April 30th during which snow condition is assumed to be dry.