Multiwavelength, aerosol lidars at Maïdo supersite, Reunion Island, France: instruments description, data processing chain and quality assessment

Abstract

Abstract. Understanding optical and radiative properties of aerosols and clouds is critical to reduce uncertainties in climate models. For over 10 years, the Observatory of Atmospheric Physics of La Réunion (OPAR) has been operating three active lidar instruments (named Li1200, LiO3S and LiO3T) providing time-series of vertical profiles from 3 to 45 km of the aerosol extinction and backscatter coefficients at 355 and 532 nm, as well as the linear depolarization ratio at 532 nm. This work provides a full technical description of the three systems, details about the methods chosen for the signal preprocessing and processing, and an uncertainty analysis. About 1737 night-time averaged profiles were manually screened to provide cloud-free and artifact-free profiles. Data processing consisted in Klett inversion to retrieve aerosol optical products from preprocessed files. The measurement frequency was lower during the wet season and the holiday periods. There is a good correlation between the Li1200 and LiO3S in terms of stratospheric AOD at 355 nm (0.001–0.107; R = 0.92 ± 0.01), and with the LiO3T in terms of Angström exponent 355/532 (0.079–1.288; R = 0.90 ± 0.13). The lowest values of the averaged uncertainty of the aerosol backscatter coefficient for the three time-series are 64.4 ± 31.6 % for the LiO3S, 50.3 ± 29.0 % for the Li1200, and 69.1 ± 42.7 % for the LiO3T. These relative uncertainties are high for the three instruments because of the very low values of extinction and backscatter coefficients for background aerosols above Maïdo observatory. Uncertainty increases due to SNR decrease above 25 km for the LIO3S and Li1200, and 20 km for the LiO3T. The LR is responsible for an uncertainty increase below 18 km (10 km) for the LiO3S and Li1200 (LiO3T). The LiO3S is the most stable instrument at 355 nm due to less technical modifications and less misalignments. The Li1200 is a valuable addition to fill in the gaps in the LiO3S time-series at 355 nm or for specific case-studies about the middle and low troposphere. Data described in this work are available at https://doi.org/10.26171/rwcm-q370 (Gantois et al., 2024).