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Atmospheric and Oceanic Optics

2017 year, number 10

Variability of condensation properties of the mixed smoke from biomass burning at different stages of its evolution

V.S. Kozlov, R.F. Rakhimov, 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: смешанный дым, относительная влажность воздуха, поляризационный спектронефелометр, обратная задача, оптические и микрофизические характеристики частиц, сажа, mixed smoke, relative humidity of air, polarization spectronephelometer, inverse problem, optical-microphysical characteristics of particles, soot

Abstract

The variability of the optical-microphysical properties of the mixed wood smoke is studied in the Large Aerosol Chamber of IAO SB RAS (volume 1800 m3) during smoke aging for six days with periodic changes in the relative humidity of air within the range 45-95%. The dynamics of the size distributions and complex refractive indices for the ultrafine, fine, and coarse particles, their effective radii, lidar scattering parameter, and the single scattering albedo in the visible are analyzed on the basis of the results of detailed nephelometric measurements of the angular scattering coefficients and solution of the inverse problem. It is found that both quantitative and qualitative features of the variations in the optical-microphysical parameters vary significantly with the air humidity at different stages of the smoke aging. The key factors of the mixed smoke variability are the physical-chemical heterogeneity of three fractions of smoke particles and physical processes, such as migration of ultrafine BC particles (< 100 nm) in the size spectrum due to coagulation and the condensation growth of smoke particles. Interconnected effects (interference) of the mentioned processes on the particle’s structure determine the main features of the dynamics of the composition and absorbing properties of the smoke particles.