Tracking Land-Falling Atmospheric Rivers

Applications of the global positioning system (GPS) and other global navigation satellite systems (collectively referred to as GNSS) have become a pervasive presence for spatial awareness in the modern world. For geodetic applications, GNSS provides a global reference frame defined by the precise mm-level positions of a network of continuously monitoring stations, and the tracked orbits of the GNSS satellites (>100 currently available). A typical GNSS station fields a geodetic quality GNSS receiver and antenna, a power source (e.g., solar), and a communications method (e.g., cell modems, microwave) to transfer data to a central location for analysis (Fig. 1). Regional GNSS networks have been established for a range of applications. In California, there are about 1000 GNSS stations1 that precisely map crustal movements across the transition from North American to the Pacific tectonic plates (Fig. 2), occurring over a zone several hundreds of kilometers wide. Occasional large earthquakes can displace the position of a station by more than a meter. The coordinates of these stations and their changes in time (displacements) define a statewide geodetic datum maintained by the California Spatial Reference Center (CSRC)2 and tied to the National Spatial Reference System (NSRS) defined and maintained by NOAA's National Geodetic Survey (NGS)3.