Assessment of aerosol's mass concentrations from measured linear particle depolarization ratio (vertically resolved) and simulations

[摘要] Multi-wavelength depolarization Raman lidar measurements from Magurele,Romania are used in this study along with simulated mass-extinctionefficiencies to calculate the mass concentration profiles of differentatmospheric components, due to their different depolarization contribution tothe 532 nm backscatter coefficient. Linear particle depolarization ratio(δ^part) was computed using the relative amplification factorand the system-dependent molecular depolarization. The low depolarizingcomponent was considered as urban/smoke, with a mean δ^partof 3%, while for the high depolarizing component (mineral dust) a meanδ^part of 35% was assumed.

For this study 11 months of lidar measurements were analysed. Two study casesare presented in details: one for a typical Saharan dust aerosol intrusion,10 June 2012 and one for 12 July 2012 when a lofted layer consisting ofbiomass burning smoke extended from 3 to 4.5 km height.

Optical Properties of Aerosols and Clouds software package (OPAC)classification and conversion factors were used to calculate massconcentrations. We found that calibrated depolarization measurements arecritical in distinguishing between smoke-reach aerosol during the winter anddust-reach aerosol during the summer, as well as between elevated aerosollayers having different origins. Good agreement was found between lidarretrievals and DREAM- Dust REgional Atmospheric Model forecasts in cases ofSaharan dust. Our method was also compared against LIRIC (TheLidar/Radiometer Inversion Code) and very small differences were observed.

[学科分类] 几何与拓扑