Observation of In-Cirrus Contrail Properties Using Airborne Lidar-Radar Remote Sensing

Persistent contrails have a significant influence on Earth's energy balance, yet their effects within existing cirrus clouds remain underexplored. This study investigates embedded contrails using observations from the HALO aircraft during the ML-CIRRUS, CIRRUS-HL, and NAWDEX campaigns, alongside lidar-radar retrieval data from the VarCloud framework. We developed an automated detection method leveraging WALES lidar parameters, focusing on particle backscatter coefficients (β(λ) > 4 Mm^⁻¹ sr^⁻¹) and linear depolarization ratios (δ(λ) < 30% or 43%, based on background pollution) to identify contrail regions accurately. Our results reveal that embedded contrails have a smaller ice effective radius and increased ice water content in affected cirrus clouds by aviation, indicating that they can significantly modify the microphysical properties of cirrus clouds. This understanding is essential for evaluating the climate impact of aviation and for enhancing detection techniques in spaceborne observations, such as those from the EarthCare satellite.