Airborne forward pointing UV Rayleigh lidar for remote clear air turbulence (CAT) detection: system design and performance

TL;DR

This paper presents a high-performance airborne UV Rayleigh lidar system designed to detect clear air turbulence (CAT) by measuring air density fluctuations, demonstrating its effectiveness in cruise flight conditions at various distances.

Contribution

The paper introduces a novel airborne UV Rayleigh lidar system for detecting CAT based on air density fluctuations, suitable for commercial aviation safety.

Findings

Successfully detects light-to-moderate CAT at 5 km

Detects moderate CAT at 10 km

System stability is adequate for commercial use

Abstract

A high-performance airborne UV Rayleigh lidar system was developed within the European project DELICAT. With its forward-pointing architecture it aims at demonstrating a novel detection scheme for clear air turbulence (CAT) for an aeronautics safety application. Due to its occurrence in clear and clean air at high altitudes (aviation cruise flight level), this type of turbulence evades microwave radar techniques and in most cases coherent Doppler lidar techniques. The present lidar detection technique relies on air density fluctuations measurement and is thus independent of backscatter from hydrometeors and aerosol particles. The subtle air density fluctuations caused by the turbulent air flow demand exceptionally high stability of the setup and in particular of the detection system. This paper describes an airborne test system for the purpose of demonstrating this technology and turbulence detection method: a high-power UV Rayleigh lidar system is installed on a research aircraft in a forward-looking configuration for use in cruise flight altitudes. Flight test measurements demonstrate this unique lidar system being able to resolve air density fluctuations occurring in light-to-moderate CAT at 5 km or moderate CAT at 10 km distance. A scaling of the determined stability and noise characteristics shows that such performance is adequate for an application in commercial air transport.