A–WALI: An Airborne Raman Lidar for Aerosol, Cloud, Temperature, and Water Vapor Observations during MAESTRO

Abstract. In preparation for the MAESTRO (Mesoscale Organisation of Tropical Convection) airborne campaign conducted off Cabo Verde in August–September 2024, the Airborne Weather and Aerosol Lidar (A-WALI) was developed to characterize the horizontal distributions of clouds, aerosols, water vapor, and atmospheric temperature through a side window of the SAFIRE ATR-42 research aircraft. This compact Raman lidar operates at 355 nm and combines a 15 cm telescope with a diode-pumped laser delivering 60 mJ pulses at a repetition rate of 200 Hz. Its measurement performance was assessed through end-to-end simulations, ground-based observations, and airborne measurements. A-WALI successfully resolves cloud and aerosol structures. Under nighttime conditions, water vapor mixing ratios can be retrieved over distances of approximately 2–3 km with a statistical uncertainty below 0.5 g kg⁻¹, while temperature retrievals achieve an uncertainty below 0.5 °C over distances of approximately 1 km. At shorter measurement ranges (≤ 2 km), fluctuations in water vapor and temperature can be resolved under both daytime and nighttime conditions. Comparisons with in situ measurements support the calibration and validation of the retrievals, demonstrating the potential of A-WALI to investigate the horizontal variability of atmospheric thermodynamic properties, clouds, and aerosols from an airborne platform.