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Proceedings Paper

Variations of microphysical parameters of atmospheric aerosol on spectropolarimetrical investigations
Author(s): Andrey A. Isakov
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Paper Abstract

Some preliminary results of investigations of optical and microphysical characteristics of surface layer aerosol by means of spectropolarimeter are presented. The daily measurements were carried out in February - April 2000 at Zvenigorod Scientific Station of the Institute of Atmospheric Physics. Spectropolarimeter measured the spectral dependencies of the polarization components of direct scattering coefficient D at three angles (phi) equals 45 degrees, 90 degrees, 135 degrees in spectral region (lambda) equals 0.4 - 0.75 mcm. During measurements period about 900 records were obtained. On the base of this optical information, the inverse problem was solved -- particle size distributions and complex refractive indices n + ik were obtained. The statistical behavior of some optical and microphysical characteristics and their connections with basical input modeling parameter -- scattering coefficient (sigma) was considered. It was established that the spectral dependencies of D are described good by Angstrom's formula D approximately (lambda) -(alpha ), and the high correlation between (sigma) and Angstrom's exponent (alpha) exists (the correlation coefficient R approximately equals 0.7). The refractive index of 'dry' aerosol is also correlated with (sigma) , i.e. the mean chemical composition of aerosol particles changes with (sigma) change. The instrument was supplied by an air flow heater which allowed to measure the optical characteristics of 'dry' aerosol and to estimate the aerosol condensation activity. The last can be estimated from the reaction of aerosol optical characteristics on variations of the relative humidity Rh of air and is described often by so-called Hanel's formula D approximately (1-Rh)-(chi ). The (chi) parameter was estimated for about 500 realizations of directed scattering coefficients D. It was found that its distribution is close to normal one with mean value (chi) equals 0.55 and variance S equals 0.3. The close connection between (chi) and scattering coefficient (sigma) of dry aerosol is absent (correlation coefficient R equals 0.35), but with (sigma) decrease, the variance of (chi) increases strongly. The dependencies of the sensitivity of different particle sizes e (eta) (r) on Rh changes were also considered.

Paper Details

Date Published: 29 December 2000
PDF: 8 pages
Proc. SPIE 4341, Seventh International Symposium on Atmospheric and Ocean Optics, (29 December 2000); doi: 10.1117/12.411997
Show Author Affiliations
Andrey A. Isakov, Institute of Atmospheric Physics (Russia)

Published in SPIE Proceedings Vol. 4341:
Seventh International Symposium on Atmospheric and Ocean Optics
Gennadii G. Matvienko; Mikhail V. Panchenko, Editor(s)

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