6.2.1 Microwave wavelengths

Remote sensing of snow cover is done by low-orbiting satellites that have the spatial and temporal resolution required for accurate snow-related measurements.

Satellite observations have advantages over traditional ground measurements. For example, they cover large areas with near-uniform resolution and retrieve data from remote regions of the world where onsite measurements can be time consuming or nearly impossible to take.

Aqua AMSR-E 89GHz three-day average of snow and ice cover over North America on 26 April, 2006.

Microwave wavelengths are best for assessing snow properties from a remote sensing perspective—far more so than visible or infrared wavelengths. That’s because microwave energy can penetrate snowpack and is reflected and emitted both from the surface and deeper within the pack. This makes it sensitive to parameters such as snow depth, snow water equivalent, snowpack temperature, snow crystal type, wet-dry state, as well as soil conditions below the snowpack.

In addition, microwave instruments also penetrate cloud cover and operate during both day and nighttime. This makes them useful for detecting snowpack conditions on a 24-by-7 basis.

The rest of this section presents products made from satellite-derived snow observations.