I remember years ago hearing about radar using GPS to pinpoint just how close the rain was to you!
I know we all take that for granted now (see my app!), but most of us just think of GPS as a location device -- where am I? where am I going? We use GPS to navigate with our cars and on our smartphones. New apps always ask permission to “know our location.” On crime shows you’ve seen investigators using GPS triangulation to locate someone’s cell phone.
The bottom line is, GPS is all about the location of something and when that location changes due to movement. And that’s where using GPS for forecasting comes in: following things that move.
For instance, consider the earth moving during an earthquake: GPS can be used to track subtle underground movements, whether the seafloor or a land fault. Spotting those shifts quickly helps warn of the earthquake’s magnitude and which cities will be affected by the moving land!
From earthquakes to volcanoes, GPS can detect movements underground as magma shifts, indicating an eruption coming. In addition, by following how ash plumes move, scientists can better forecast just how high that plume might go (an important forecast for pilots trying to navigate around ash).
GPS also detects not just beams coming down from satellites, but beams bouncing up, off the earth: knowledge that can measure snowpack in remote regions. That measurement can forecast snowmelt runoff and flooding as well as ice sheet thickness (think climate change). Those same kinds of reflections can forecast tidal changes.
For us, GPS is being used more and more to forecast flooding. Water vapor can delay GPS signals traveling through the atmosphere, thus indicating more precipitable water and that knowledge helps forecasters predict how much rain or snow may develop. Scientists have successfully warned of monsoon flooding minutes before occurring.
I’ve summed up some of the exciting advances going on with GPS (who knew?) but I encourage you to have a look at a terrific article for more in-depth explanations at Knowable Magazine.