Abstract
Abstract. Multi-wavelength depolarization Raman lidar measurements from Magurele, Romania are used in this study along with simulated mass-extinction efficiencies to calculate the mass concentration profiles of different atmospheric components, due to their different depolarization contribution to the 532 nm backscatter coefficient. Linear particle depolarization ratio (δpart) was computed using the relative amplification factor and the system-dependent molecular depolarization. The low depolarizing component was considered as urban/smoke, with a mean δpart of 3%, while for the high depolarizing component (mineral dust) a mean δpart of 35% was assumed. For this study 11 months of lidar measurements were analysed. Two study cases are 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 of biomass 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 mass concentrations. We found that calibrated depolarization measurements are critical in distinguishing between smoke-reach aerosol during the winter and dust-reach aerosol during the summer, as well as between elevated aerosol layers having different origins. Good agreement was found between lidar retrievals and DREAM- Dust REgional Atmospheric Model forecasts in cases of Saharan dust. Our method was also compared against LIRIC (The Lidar/Radiometer Inversion Code) and very small differences were observed.
Highlights
In recent years, there has been a substantial increase in studying the influence of aerosols on the climate through both direct and indirect radiative effects (Lesins et al, 2002)
The method developed for the retrieval of the partial and total mass concentration profiles is useful to study special cases such as Saharan dust outbreaks and biomass burning events, and to study seasonal variability of local aerosol
Mass concentration profiles for mixed aerosols have been calculated from multi-wavelength depolarization Raman measurements, by considering low and high depolarizing components along with OPAC data
Summary
There has been a substantial increase in studying the influence of aerosols on the climate through both direct and indirect radiative effects (Lesins et al, 2002). Several techniques have been developed to separate the fine (biomass burning smoke, urban haze) and coarse (sea salt, desert dust) aerosol profiles (Tesche et al, 2009a, b, and references within), with the scope of retrieving the mass concentration. Some of these methods separate the coarse mode in coarse spherical and coarse non-spherical particles. Ansmann et al (2012) presented an extended review of recent measurements of mass extinction efficiencies (defined as the ratio of aerosol mass concentration to extinction coefficient) for Saharan and volcanic dust Such specific extinction coefficients are required to convert measured particle optical properties into mass concentration information.
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