AIRflows - a novel airborne Doppler lidar for high resolution wind measurements

Wind is a core state variable of the atmosphere. Extending the capabilities of ground-based measurement systems, airborne Doppler lidar (ADL) onboard research aircraft allows for targeted and spatially resolved wind measurements, which are crucial for localized severe weather events or in inaccessible regions such as over water and complex terrain.

A novel ADL system – AIRflows (‘AIRborne fixed-beam lidar for wind measurements‘)  – has been developed by the Karlsruhe Institute of Technology (KIT) in collaboration with scientific and industrial partners during the last two years.
Up to now, ADL systems use a single Doppler lidar attached to a scanner to provide radial velocity measurements under multiple viewing angles. Multiple viewing angles are needed to reconstruct the 3D wind from the unidirectional radial velocity measurements. Due to cost and size reductions of Doppler lidar units over the recent years, it has now become possible to construct an ADL system that uses multiple lidars with fixed-direction beams, instead of a single lidar with a scanning beam. The simultaneous availability of multiple viewing angles brings advantages: Simulation results have demonstrated that a multi-lidar system can achieve approximately one order of magnitude improved spatial wind measurement resolution as well as higher accuracy, compared to existing scanning systems.

This contribution presents the novel AIRflows system developed by KIT. AIRflows implements the novel fixed-beam, multi-lidar concept onboard the TU Braunschweig Cessna F406 research aircraft. The system uses five modified Doppler lidar modules manufactured by Abacus Laser, one pointing nadir and the other four pointing forward, aft, left and right at an elevation of 30° from nadir.
The first flights deploying AIRflows have been successfully completed during summer 2024. Initial analysis demonstrates wind profiles at 100 m spatial resolution, allowing to resolve fine-scale 3D winds inside the PBL for the first time. As part of the tests, flights to the Alps were conducted in preparation for the upcoming international TEAMx campaign. AIRflows measurements across Alpine valleys and crests provide previously unattainable insight into vertical wind and valley circulations in complex terrain. Similarly, AIRflows measurements across a wind farm in the North Sea provide novel vertically resolved insight into wind farm wake behavior.

Overall, AIRflows revolutionizes the field of airborne wind measurements by providing an order of magnitude improved spatial resolution as well as higher measurement accuracy, compared to previously existing ADL.