Scientists Look to Skies to Improve Tsunami
A team of scientists from Sapienza University in Rome, Italy, and NASA’s Jet Propulsion Laboratory in Pasadena, California, has developed a new approach to assist in the ongoing development of timely tsunami detection systems, based upon measurements of how tsunamis disturb a part of Earth’s atmosphere.
The new approach, called Variometric Approach for Real-time Ionosphere Observation, or VARION, uses observations from GPS and other global navigation satellite systems (GNSS) to detect, in real time, disturbances in Earth’s ionosphere associated with a tsunami. The ionosphere is the layer of Earth’s atmosphere located from about 50 to 621 miles (80 to 1,000 kilometers) above Earth’s surface. It is ionized by solar and cosmic radiation and is best known for the aurora borealis (northern lights) and aurora australis (southern lights).
When a tsunami forms and moves across the ocean, the crests and troughs of its waves compress and extend the air above them, creating motions in the atmosphere known as internal gravity waves. The undulations of internal gravity waves are amplified as they travel upward into an atmosphere that becomes thinner with altitude. When the waves reach an altitude of between 186 to 217 miles (300 to 350 kilometers), they cause detectable changes to the density of electrons in the ionosphere. These changes can be measured when GNSS signals, such as those of GPS, travel through these tsunami-induced disturbances.