We’ve previously written about how GPS technology is used for early warning systems for earthquakes and tsunamis. GPS stations on the ground detect slight changes and movements on the earth’s crust. By monitoring the existing extensive network of GPS stations, researchers can know an earthquake is coming before the violent shaking begins. Tsunamis, which are caused by earthquakes, can also be predicted with GPS tracking systems on the ground. We are all too familiar with the devastation these natural disasters can cause, so the earlier the warning, the more lives can be saved.
Scientists have now discovered a way to use the technology to predict other hazardous events, like flash flooding. A team of researchers from NASA’s Jet Propulsion Laboratory, the Scripps Instituion of Oceanography and the National Oceanic and Atmospheric Administration are using GPS stations to develop early warning systems for hazardous storms. The technology that allows GPS to detect small movements also can measure water vapor in the air.
“A GPS receiver fundamentally is measuring the amount of time it takes signals to travel from the GPS satellites to the receiving antenna on the ground,” Angelyn W. Moore, JPL’s Geodynamics and Space Geodesy group scientist, explained. “That travel time is modified by the amount of water vapor in the atmosphere. The upshot is that whenever we measure a geodetic-quality GPS station’s position, we are also measuring the delay due to water vapor. That delay can be related to precipitable water vapor with the surface pressure and temperature measurement.”
By combining the data received from the GPS stations, thermometers and barometers, weather forecasters can predict flash flood risk with much greater accuracy. There are currently around 40 weather stations tracking water vapor, and delivering estimates every half hour. However, the team hopes to improve the system to provide vapor estimates at a much more frequent rate. “We are evaluating hardware to provide water vapor [data] at 5 minutes or less at a test site, and plan to install that at approximately 25 sites,” Moore added. Currently, weather forecasters have to look up the vapor measurements via a Web interface, but Moore hopes to improve that soon as well, saying, “We are pursuing integration into their standard forecaster displays.
The GPS technology is great for measuring larger movements on the ground caused by earthquakes, while accelerometers are better for capturing smaller changes in location. The accelerometers can even detect P-waves, which preface the more powerful S-waves of earthquakes that we feel during the violent shakes or rolling waves of the quake. The properties of the P-wave can help seismologist predict the strength of the S-waves, and also allow for earliest detection and warning systems for the earthquake.
There are currently 475 GPS stations in Southern California, alone. 175 of those stations operate in real-time. Only 17 of them are equipped with accelerometers. California has a much higher density of GPS stations than say Ohio, because of the frequency of earthquakes in the region. Many of these stations were developed with earthquake detection as the primary purpose. There are no current plans to expand the stations, but Moore suggests it would be very valuable to do so.
“Certainly the spacial extent can be extended,” she said. “Existing real-time GPS stations tend to be located in California more than in Arizona, so north is the most obvious opportunistic direction at present. That would enable use of the GPS water vapor [data] for other weather conditions such as atmospheric rivers (ARs).” Atmospheric rivers are pretty similar to what you’d think. It describes and atmospheric phenomenon in which a narrow, river-like collection of water vapor in the air is transported horizontally. “While ARs come in many shapes and sizes, those that contain the largest amounts of water vapor, the strongest winds, and stall over watersheds vulnerable to flooding, can create extreme rainfall and floods.”
The GPS-enabled weather stations can monitor large amounts of water vapor across Southern California. When an AR is detected above or approaching an area that is at high risk for flooding, an early warning system can be established. This way, people can better protect their loved ones and their property. Flash flooding can be very serious, causing damage to homes and cars. These sudden floods also threaten the lives of people and their pets. With better warning systems, people will be more prepared when natural disasters strike.
According to the NOAA, there are already several hundred GPS weather stations across the United States. Unfortunately, they are all too far apart to serve the purposes of water vapor tracking. However, they could be used in the future for this purpose, if the system works well enough in California.
GPS Technology Used for Early Warning Weather Forecasting
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