The system also can quickly assess potential damage to buildings, bridges, and other structures due to ground displacement after an earthquake.
For meteorological monitoring, GPS receivers are outfitted with temperature and pressure sensors to provide a continuous map of atmosphere water vapor.
"A GPS station fundamentally is measuring the amount of time it takes signals to travel from the GPS satellites to the receiving station on the ground. That travel time also is affected by the amount of moisture in the air, so every time we calculate the position of a GPS station, we're also measuring the water vapor," said Angelyn Moore, a research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"Using GPS for weather is not new. What's new is that there are now sufficient numbers of stations in the southern California region operating near real-time for us to evaluate the benefit," she said.
The first test run of the system occurred in July when meteorologists tracked a summer monsoon as it moved across southern California. Equipped with real-time information about the storm's progress based on GPS signals, forecasters accurately predicted a flash flood and issued a warning.