Aerosol variability over oceans using micro-pulse lidar and photometer: insights from TRANSAMA ship-based campaign

Abstract. The TRANSAMA campaign (Transit to AMARYLLIS-AMAGAS oceanographic cruise), conducted aboard the research vessel Marion Dufresne II assessed instrument performance and investigated aerosol properties during its transit from La Reunion Island to Barbados (April–May 2023). A set of remote sensing instruments, including two CE318-T Sun-sky-lunar photometers and a CE370 single-wavelength elastic lidar, was deployed under the MAP-IO (Marion Dufresne Atmospheric Program–Indian Ocean) framework. Performance assessments of the deployed instrumentation support the development of coupled lidar–photometer systems for shipborne atmospheric observations, while acknowledging current detection limits. Synergistic observations provided vertically resolved aerosol properties, such as extinction coefficients, alongside atmospheric structure, highlighting the marine boundary layer (MBL) top at 800 ± 300 m. While the photometer observations revealed clean atmospheric conditions over the South Atlantic (AOD440=0.08±0.04), thin aerosol layers above the MBL were identified as long-range transported residual biomass-burning-urban aerosols from Southern Africa with effective LR of 33±12 sr. Cloud layers covering a large range of altitudes (up to 16 km) were observed in 53 % of the lidar profiles, with a higher frequency at lower altitudes, where aerosol layers were more frequently detected. These findings emphasize the impact of continental aerosols on remote oceanic regions and demonstrate the capabilities of synergistic lidar–photometer measurements for advancing our understanding of aerosol variability, cloud formation, and climate processes over the oceans.