Airborne Hyperspectral LiDAR Detection of Clear Air Turbulence via Fabry–Perot Etalon Four-Edge Frequency Discrimination: Method and Simulation-Based Performance
Abstract
Remote sensing of clear-air turbulence (CAT) remains one of the most persistent safety challenges in aviation, a difficulty further exacerbated by the spatially and temporally heterogeneous nature of atmospheric aerosols. This simulation-based study presents a novel CAT detection methodology based on an UV airborne high-spectral-resolution LiDAR system. To robustly retrieve the weak molecular backscatter signals at high altitudes—where they are readily masked by aerosol backscatter—we develop a four-edge frequency discrimination module that integrates three Fabry–Perot etalons (FPEs) in a compact, tightly coupled configuration. The system is comprehensively evaluated under a broad range of CAT conditions through numerical simulations, with the FPEs having an effective reflectivity <inline-formula><tex-math notation="LaTeX">$r = 0.8620$</tex-math></inline-formula> and a circle frequency interval between the two main FPEs <inline-formula><tex-math notation="LaTeX">$\Delta \nu _{12} = 344\ \text{MHz}$</tex-math></inline-formula>. The simulation results demonstrate an atmospheric backscatter utilization efficiency of 79%, accompanied by strong suppression of aerosol backscatter. At a representative cruise altitude of 12 km, the system achieves detection of light-to-moderate CAT (EDR <inline-formula><tex-math notation="LaTeX">$= 0.3\ \mathrm{m^{2/3}\cdot s^{-1}}$</tex-math></inline-formula>) at ranges of up to 10 km. The system also exhibits favorable tolerance to FPE temperature deviations and laser frequency drifts, with detection range degradation remaining within 0.5 km for temperature variations of <inline-formula><tex-math notation="LaTeX">$0.1\; ^{\circ }$</tex-math></inline-formula>C and frequency drifts of 10 MHz, and with a correction algorithm effectively restoring performance under large frequency offsets. These results constitute a significant advance in real-time, long-range CAT detection capabilities.