Snow Cover

The timing of spring snow melt affects the length of the growing season, the timing and dynamics of spring river runoff, permafrost thawing, and wildlife populations. For many areas of the world, water availability throughout a year is dependent on how much water is stored in snow. Lack of snow water can be a leading indicator of drought and wildfire. Conversely, high snow water equivalence, combined with fast rate of melt, can be a leading indicator for flood in many parts of the world.

Snow Data Assimilation System (SNODAS) is a modelling and data assimilation system developed to provide estimates of snow cover and associated parameters to support hydrologic modelling and analysis (Barrett 2003). SNOWDAS integrates multiple data sources including satellite and ground based data into a snow model to produce snow depth and snow water equivalent data. This data allows us to understand both snow depth as well as the depth of water if snow were to melt completely.

Normalized Difference Snow Index (NDSI) provides information on snow cover. It typically ranges from -1 to 1, with values from 0.5 to 1 representing snow coverage. Information on snow coverage and depth is an important resource in water resource management, planning, and forecasting. Monitoring snow extent using satellite imagery is useful for understanding snow depletion and recession rates, evaluating snow extent relative to long term average conditions, and is a useful drought metric.