Séminaire

Vendredi 12 Mai 2023 à 11h00.

Characterization of atmospheric aerosol physical properties based on Raman, fluorescence and elastic backscatter lidar measurements.

''Interaction of laser with atmospheric particles is accompanied by numerous physical processes, such as Mie scattering, change of polarization state, Raman scattering and laser induced fluorescence. Thus, analysis of corresponding backscatters allows to obtain information about particle properties remotely. This presentation will be focused at the following topics: • Study of African dust with multiwavelength polarization Mie-Raman lidar. Increase of the imaginary part of dust refractive index in UV leads to spectral dependence of the backscattering coefficient and the lidar ratio. Comparison of observed values with simulations based on the model of randomly oriented spheroids allows to estimate increase of the imaginary part. • Particle classification based on fluorescence measurements. Joint use of fluorescence and depolarization lidar measurements allows to identify main aerosol types, such as dust, smoke, pollen and urban particles. • Aerosol fluorescence inside ice clouds. Aerosol concentration near the cloud base and inside the ice cloud can be estimated from fluorescence measurements using the conversion factors. Obtained values are used for the study of ice formation in the presence of dust, pollen and smoke particles. • Fluorescence technique in application to the study of the particle hygroscopic growth. The water uptake increases the elastic backscattering but normally does not alter the chemical components, so total amount of fluorescent molecules within a particle does not change. The synergy of multiwavelength and fluorescence lidar measurements allows to estimate volume fractions of dry matter and water in the particle.''