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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:04 |
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Conference: Bucharest University Faculty of Physics 2009 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Using direct sun-photometry data for rapid estimation of some key parameters of the atmospheric aerosol
Authors:
Luminita Filip and Sabina Stefan
Affiliation:
University of Bucharest, Faculty of Physics, Bucharest-Magurele 077125, P.O. Box MG-11, Romania; Phone/Fax: (+4021) - 457.45.21
E-mail
sabina_stefan@yahoo.com
Keywords:
atmospheric aerosol, aerosol optical depth,climate
Abstract:
The atmospheric aerosol plays an extremely important role in the energetic balance of the Earth-atmosphere system, thus dramatically influencing the climate evolution at both local and global levels. In this paper a rapid and simple method is proposed to obtain useful quantitative information on the relative contribution to the ground solar irradiation extinction of the two main aerosol modes (fine and coarse), by using only single scattering data provided by direct sunlight photometric measurements (or sun-photometry). The method is based on defining the separate contributions to the aerosol optical depth (AOD) of each separate aerosol mode and on expressing AOD as a linear combination of the aerosol contents of each mode. The coefficients of such a linear combination are quantities dependent only on the dimensional parameters of the particles in each mode and on the wavelength of the analyzed light. These coefficients can be conveniently obtained theoretically within the framework of Mie theory of light scattering on spherical particles. Experimental AOD spectral variation provided by a publicly accessible database like AERONET can be used to compute the spectral dependence of the Ångström parameter. Moreover, both AOD and Ångström parameter spectral diagrams can be compared and fitted with their theoretical counterparts to retrieve the optical ratio of the fine and coarse modes and the relative contamination of the atmospheric column with fine aerosol (usually of antropic origin). Some size parameters (i.e. modal radii and widths) needed to describe the size distribution in a log-normal, bi-modal analytical model can be also estimated. Validation of the method by comparing its results with those produced by inversion algorithms of almucantar data is also provided in the paper.
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