Properties of atmospheric aerosol in the plumes of forest fires according to the spectronephelometric measurements
R.F. Rakhimov, V.S. Kozlov, M.V. Panchenko, A.G. Tumakov, V.P. Shmargunov
V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, 1, Academician Zuev square, Tomsk, 634021, Russia
Keywords: smokes of forest fires, natural measurements, angular polarization spectronephelometry, optical and microphysical properties, soot
Abstract
A cycle of measurements of the angular aerosol scattering coefficients under conditions of extremely dense smoke haze from Siberian forest fires has been carried out in Tomsk in July–August of 2012 with the aid of a polarization spectronephelometer. The size spectrum of the smoke haze had the ultra-fine (particle radius < 150 nm) and medium (with a mode of the volume distribution near 350 nm) fractions. The effective radius of particles was about 220 nm. The smoke haze was characterized by a weak absorption: the imaginary part of the refractive index of the ultra-fine and medium particles had values of ~ 0.038 and ~ 0.012, respectively. The mean value of the single scattering albedo at a wavelength of 525 nm was about 0.91. At the “decay” of smoke haze (in peripheral zones of smoke plumes), the optical contribution from the ultra-fine fraction increases, which shows itself in the increase of the imaginary part of the refractive index of ultra-fine particles up to ~ 0.5 and a decrease of albedo from 0.91 to 0.84.
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