Snow Cover is a raster data layer indicating the presence of snow on the ground, used in Technosylva products to account for the fire-suppressing and fuel-modifying effects of snowpack. The data source varies by geography: customers within the contiguous United States (CONUS) receive snow cover derived from Snow Data Assimilation System (SNODAS), while customers outside CONUS receive a Technosylva-calculated product derived from Visible Infrared Imaging Radiometer Suite (VIIRS) surface reflectance data.
Snow Data Assimilation System (SNODAS)
Snow Data Assimilation System (SNODAS) is a modeling and data assimilation system developed by NOAA's National Operational Hydrologic Remote Sensing Center (NOHRSC) to estimate snow pack properties across the contiguous United States. It provides daily estimates of snow depth and snow water equivalent (SWE) at 1 km x 1 km spatial resolution.
Technosylva uses the SNODAS product (NSIDC G02158) with a snow depth filter applied to reduce the tendency of the raw product to overestimate snow cover extent. Pixels below the depth threshold are not classified as snow-covered.
Source: NSIDC G02158 — Snow Data Assimilation System (SNODAS) Data Products, Version 1
Temporal resolution: 1 day
Spatial resolution: 1 km x 1 km
Coverage: CONUS
Visible Infrared Imaging Radiometer Suite Snow Cover (VIIRS)
VIIRS Snow Cover is a Technosylva-calculated snow cover product for areas outside the contiguous United States, derived from the NASA/NOAA Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS) daily surface reflectance data (VNP09GAv002). The product combines the Normalized Difference Snow Index (NDSI), a data collection confidence flags band, and a water body mask to classify snow-covered pixels.
Source: VNP09GAv002 — VIIRS/NPP Surface Reflectance Daily L2G Global 1 km and 500 m SIN Grid, Version 2
Temporal resolution: 1 day
Spatial resolution: 500 m x 500 m
Coverage: Outside CONUS