Aerosol hygroscopic growth study from synergy between Mie-Raman-Fluorescence Lidar and Microwave Radiometer

This study focuses on the characterization of aerosol hygroscopicity using remote sensing techniques. A Mie-Raman-Fluorescence lidar, developed at the Laboratoire d’Optique Atmosphérique in Lille, France, in combination with a Microwave radiometer, allow to monitor continuously both aerosols and water vapor. Hygroscopic growth cases can be identified when an aerosol layer presents an increase in both aerosol backscattering coefficient and relative humidity. Looking at the class of the aerosol among the layer, determined from clustering methods, and the fluorescence backscattering coefficient, which is expected to be unaffected by the presence of water, it is possible to verify that the aerosol layer is homogeneous. Therefore, the change in the backscattering coefficient is then only due to water uptake. The Hänel theory describes the evolution of the backscattering coefficient with relative humidity and introduces a hygroscopic coefficient, γ which depends on the aerosol type and the relative humidity threshold of the dry condition. One case study has been identified on 10 March 2021 for a smoke aerosol layer. For this case, γ was determined at  for . This value is consistent with other values found in the literature for smoke particles. Other cases have been analyzed and this set of example illustrates the potentiality of the methodology presented here.