The LIDAR sensor mounted on the aircraft

LIDAR-based tool forecasts clear-air turbulence

An instrument based on the Light Detection and Ranging technology to help pilots detect dangerous turbulence has been developed by the German Aerospace Centre.

The device that can be mounted on aircraft emits short-wave ultraviolet laser pulses along the direction of the flight. Being reflected by the air molecules, the signal’s back-scatter shows fluctuations in the density of the atmosphere. The pilots can thus see in real time whether there is any clear-air turbulence (CAT) in the region they are about to enter.

CAT appears independently of cloud cover and has so far been impossible to predict. Despite usually not putting the safety of the flight at risk, the turbulence might be a highly unpleasant and scary experience for the passengers, sometimes even resulting in injury. Several recent studies have shown that incidence and severity of turbulences is rising due to climate change.

The development of a turbulence-predicting tool has therefore become a priority of the atmospheric research community. A team from DLR’s Institute of Atmospheric Physics has managed to develop a prototype tool in the framework of the Demonstration of LIDAR based Clear Air Turbulence detection project (DELICAT).

The system is currently being tested on-board a specially modified Cessna Citation aircraft. The plane will be taking measurements travelling from Amsterdam to various European destinations until the end of August.

Following the end of the data-collection campaign, the researchers will tune the instrument for further commercial development. In the long term, such a device could be installed on every passenger jet to allow pilots to either avoid turbulent regions or at least warn the passengers beforehand.

The measurements will also help the researchers to advance their understanding of the atmospheric processes that lead to CAT.

During CAT, wind shear often occurs along the jet stream at the altitudes where aircraft travel. This turbulence involves large layers of air moving against each other horizontally at different speeds. Particularly strong wind shear can create waves that ultimately break similarly to those on water. When a wave breaks turbulence or vortices occur.

The DELICAT project, launched in 2009 and funded by the European Union involves cooperation of a wide variety of European companies and institutions. Coordinated by DLR and Thales, the project includes participants from 12 European countries.

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