Snow measurements are needed both to study climate and to predict drought, flooding, and water availability. In urban areas, weather spotter networks and citizen scientists measure snow depth. However, information about snow depth is more difficult to obtain in remote areas that are sparsely populated. Measuring snow is also difficult because it is highly variable in space and time.
The U.S. national snow network (SNOTEL) has a large number of sensors in the western United States, but these sensors have fairly small sensing regions (a few square meters). Satellites – which in principle would be able to provide the large picture – do not currently provide accurate estimates of snow depth.
GPS Interferometric Reflectometry (GPS-IR) is a new method to measure snow depth. It has a footprint of ~1000 square meters. It was developed at the University of Colorado with our research partners at UCAR and NOAA. Our PBO H2O project now routinely measures snow depth for 210 sites in North America. Any geodetic quality GPS site can be used to measure snow depth if the site is surrounded by natural, planar surfaces. We routinely use GPS sites operated by the Minnesota Department of Transportation and NRCan. Our newest GPS snow site is operated by the FAA in Nunavut, Canada.