Development of Aerosol Typing Algorithm with Airborne Lidar Data

The monitoring of aerosols and air quality is important due to their influence on both the Earth system and also human health. Aerosols can change atmospheric circulation, affect the radiation budget, alter cloud processes, reduce visibility, and are also attributed to respiratory diseases. Lidar observations from instruments such as the Cloud Physics Lidar (CPL; McGill et al. 2002) provide important observations of the optical properties of aerosols along with their vertical distribution in the atmosphere. CPL is a multi-wavelength (355, 532, 1064nm) elastic lidar system built for deployment on the NASA ER-2 high altitude aircraft and the NASA Global Hawk UAV. At each wavelength CPL measures total attenuated backscatter as a function of altitude providing a comprehensive suite of products for optically thin cirrus and aerosol layers. Cloud and aerosol products provided by CPL data include particle depolarization ratio at 1064nm, lidar ratios, extinction coefficient, optical depth, and backscatter color ratio. The lidar ratio for transmissive cloud and aerosol layers can be directly derived using CPL measurements of optical depth and total integrated backscatter, yielding the internal extinction profile of an aerosol layer, and allowing for the direct solving of the lidar equation without the assumption of aerosol climatology. Lidar data from instruments such as CPL provide critical observations of the vertical profile of clouds, aerosols, and their associated optical properties. Specifically for aerosols, observations of the integrated total attenuated backscatter and depolarization ratios yield the location of the aerosol layer and the particle shape, respectively, which then advances our understanding of impact on regional air quality. Current CPL layer type algorithms separate atmospheric layers into three categories: clouds, elevated aerosols, and PBL aerosols. This provides no information on aerosol type (i.e. dust, smoke, industrial pollution, etc.) In this study, we present a new aerosol-typing algorithm for the CPL data. This algorithm improves observations of aerosol optical properties, hence, providing more accurate information on the type of aerosol in the layer. Performance of the new algorithm is being assessed using case studies from recent CPL deployments during the NASA HS3 and SEAC4RS missions.