Early Detection of Tsunamis in the Atmosphere

OASIS observes the nightglow – commonly known as airglow – in the mid-atmosphere. Airglow is a chemical phenomenon which is initiated by the energy of the sun at daytime with the main chemical reactions happening at nighttime leading to this light emission in the atmosphere. Especially, the hydroxyl molecule leads to an intense glow in the short wave infrared range originating from about 86km altitude. Atmospheric dynamics can be investigated by measuring this glow and changes in airglow made visible in the form of signals from planetary waves, gravity waves and infrasound occurrences.

Conditions for monitoring airglow are ideal in the middle of the Atacama Desert at 2635 meters altitude. The nearest settlement is far away and the air is extremely dry and clean. The observation point is only a few kilometers from the coast of Chile, and here on South America’s west coast very strong infrasound signals can potentially arise. This is because two tectonic plates collide under the sea surface here, with the Nasca Plate shoving itself under the South American Plate, giving rise to strong earthquakes. For the coastal inhabitants, seaquakes that trigger tsunamis can have serious consequences. Tsunamis arise when the ocean surface is raised vertically. The resulting displacement of water masses spreads out from the point of origin and in shallow coastal areas can build up to meter-high tsunami waves. Such an uplift extending over a large area also generates an impulse in the atmosphere that soon encounters the airglow area where it can be measured by OASIS. This makes it possible to deduce after a quake whether a tsunami can be expected and there is time for a life-saving advance warning. In addition, the instruments in Chile contribute to obtaining a better understanding of gravity waves that are generated at mountain ranges. The measurements in the Andes complement over ten years of continuous monitoring in the Alpine region. Information about these wave phenomena can help to better understand and quantify climate signals.

For the European Southern Observatory, OASIS is interesting for another reason as well. The Paranal Observatory also houses ESO’s Very Large Telescope. The use of this expensive and elaborate infrastructure has to be planned far in advance. Airglow clouds this instrument’s view of the universe. The data routinely collected by OASIS could be used to predict at short notice the brightness of the airglow and help ESO to better take into account its influence on astronomical observations and optimize the use of the telescope.

The formal dedication of OASIS, marking the initiation of the instruments' operations, took place at the end of last week right at the foot of the Very Large Telescope (VLT). A DLR measurement container especially designed for the harsh environmental conditions and holding two camera systems, a spectrometer, and the necessary computing and communication infrastructure is located there.