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1 Acta Geophysica Polonica

1 2001

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Spectral optical thickness and aerosol size distribution of air columns at Belsk in 1993-1998

Puchalski S., Sobolewski P.

Acta Geophysica Polonica

2001

Vol. 49, nr 2

261-270

The spectral aerosol optical thicknesses (SAOT) of vertical air columns were measured by a ground-based four-channel Linke's sunradiometer at Belsk Geophysical Observatory during five years: 1993-1998. Results of measurements in the form of mean monthly values are presented. The aerosol size distribution retrieved from SAOT by means of the Randomized Minimization Search Technique algorithm and bi-modal log-normal size-distribution model is also demonstrated. The results of measurements confirm the well-known regularity that the average dependence of atmospheric extinction on wavelengths in visible range is described by exponential Angstrom's formula with exponent 1.3 š 0.6. Moreover, it is pointed out that in a few cases, in atmosphere column over Belsk Geophysical Observatory there dominated big particles, of 0.6-1.2 mim radii. However, in most cases, small, 0.15-0.30 mim particles dominated which had its impact on the average distribution during five years. It is estimated that in this period the average monthly values of the volume concentration, the mean modal radius, and the effective radius of the aerosol particles have been decreasing, but the particle number density bas increased. The "cleaning of the atmosphere" was observed, i.e., aerosol underwent transformation towards smaller particles and a decrease of particle volume concentration, proportional to the weight concentration.