Abstract
Abstract. A new method, called ElEx (elastic extinction), is proposed for the estimation of extinction coefficient lidar profiles using only the information provided by the elastic and polarization channels of a lidar system. The method is applicable to lidar measurements both during daytime and nighttime under well-defined aerosol mixtures. ElEx uses the particle backscatter profiles at 532 nm and the vertically resolved particle linear depolarization ratio measurements at the same wavelength. The particle linear depolarization ratio and the lidar ratio values of pure aerosol types are also taken from literature. The total extinction profile is then estimated and compared well with Raman retrievals. In this study, ElEx was applied in an aerosol mixture of marine and dust particles at Finokalia station during the CHARADMExp campaign. Any difference between ElEx and Raman extinction profiles indicates that the nondust component could be probably attributed to polluted marine or polluted continental aerosols. Comparison with sun photometer aerosol optical depth observations is performed as well during daytime. Differences in the total aerosol optical depth are varying between 1.2 % and 72 %, and these differences are attributed to the limited ability of the lidar to correctly represent the aerosol optical properties in the near range due to the overlap problem.
Highlights
Aerosols play an important role in the atmospheric radiation budget (IPCC, 2013)
Since the ElEx methodology is strongly dependent on the selection of pure lidar ratio and particle depolarization values, we briefly present the aerosol types that are mostly observed in Europe along with their intensive optical properties
ElEx is not limited to nighttime Raman observations, and it is applicable to daytime lidar measurements as long as the observed aerosol types have different particle depolarization ratios to permit an accurate separation between them
Summary
Depending on the aerosol type, they can absorb or scatter the incoming and outgoing radiation, warming or cooling the atmosphere; depending on their size and composition, they can act as cloud condensation nuclei, modifying cloud physical and radiative properties (Kauffman et al, 2002). Pure types of aerosols can be categorized roughly as mineral dust, sea salt, volcanic, carbonaceous, or sulfate aerosols originating from various natural and anthropogenic sources. Several lidar studies have revealed that a broad variety of aerosol mixtures occurs in the European continent (e.g., Balis et al, 2004; Papayannis et al, 2005). The mixing occurs because of the relatively long pathways of air masses across different aerosol source regions before detection over the European continent. Mixing of either marine aerosol or absorbing aerosol, or both, with dust particles may result in different optical properties.
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