An Interactive Blended Analysis of Snow Depth

A new snow depth analysis over the Northern Hemisphere using optimal interpolation has been developed at NOAA and integrated into a new version of the Interactive Multi-Sensor Snow and Ice Mapping (IMS) System. The IMS snow cover and the new snow depth analysis are important applications for National Centers for Environmental Prediction (NCEP)'s Numerical Weather Prediction (NWP) models. The snow depth analysis is computed on the IMS's 4-km grid covering the Northern Hemisphere at its snow cover-classified grid points. It blends snow depth from various sources including the AMSRE2 and the Microwave Integrated Retrieval System (MiRS), in-situ surface reports and analyst subjective determinations by their relative errors to generate an optimal 4-km snow depth analysis.

The methodology used marks scientific progress compared to existing approaches and is innovative in several key aspects. Estimates of snow depth and the associated confidence values derived interactively from the IMS analyst are integrated into the objective analysis. Additionally, snow depth climatology (in the form of snow depth-elevation equations) is also ingested into the objective analysis as pseudo-observations to improve analysis over data sparse high-elevation areas; and finally, microwave-derived snow depth is downscaled at 4-km over high-elevation terrain using the climatologically derived snow depth-elevation relationships.