Multiwavelength Raman lidar system for profiling the CCN number concentrations

Cloud condensation nuclei (CCN) play an important role in the research of cloud microphysical and aerosol–cloud interactions. This study employs a multiwavelength Raman lidar for measuring CCN concentration. First, the multiwavelength Raman lidar was used to measure the atmospheric relative humidity profile, and the combination of relative humidity and the aerosol backscattering coefficient was used to retrieve the hygroscopic growth factor. By fitting the hygroscopic growth factor using the κ kappa parameter model, the hygroscopic parameter κ kappa that characterizes the hygroscopicity of aerosols was obtained. Then, the critical activation radius of aerosols was derived using the κ –Köhler theory and hygroscopicity parameter κ kappa . Finally, the CCN number concentration was obtained by combining with the aerosol particle size distribution. Experiments were conducted to verify the feasibility of the multiwavelength Raman lidar. Results showed that the effective detection range of the lidar is approximately 0–4 km. The error of the temperature measured by the lidar at the height of 0.3–3.8 km is approximately ±1K. When the relative humidity change is 0.77–0.87, the range of the hygroscopic growth factor change is 1.06–1.10, the hygroscopic parameter γ is 0.065, and the hygroscopic parameter κ kappa is 0.009. The CCN numbers concentration decreases with height but increases closer to the cloud. The multiwavelength Raman lidar is an important tool for detection of cloud microphysical and aerosol–cloud interactions and could have scientific importance and research value, both for improved understanding of the formation of clouds and precipitation and for enhanced accuracy of weather modification.