Vol. 16, issue 10, article # 4

Isakov A. A. Optical and microphysical characteristics of forest fire smokes in Moscow region in July-September, 2002. // Atmospheric and oceanic optics. 2003. V. 16. No. 10. P. 811-816. PDF
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The results of studying smoke aerosols from forest and peatbog fires in Moscow region in summer and fall of 2002 are presented. Spectropolarimetric and nephelometric measurements were carried out at the Zvenigorod scientific station. The spectropolarimeter recorded the polarized components of the near-ground aerosol scattering phase function at three scattering angles 45°, 90°, and 135° in the wavelength range 0.4-0.76 mkm with the spectral resolution 10 nm. The use of a low-temperature air heater and record of its temperature allow estimating the aerosol condensation activity. The spectropolarimeter provided obtaining data sufficient for solution of the inverse problem of reconstructing the particle size distribution and estimating the complex refractive index of a particulate matter. The automated nephelometer conducted round-the-clock measurements of the directed scattering coefficient D11(45° , 0.54 mkm) of wet aerosol and its dry matter. More than ten smoke emissions were observed in July - September of 2002, during which the mass concentration of the submicron aerosol was 10 to 50 times higher than the mean background level. Particle size distributions were reconstructed for these episodes and complex refractive indices of a particulate matter were estimated. The characteristic particle size and distribution width of the fire smokes turned to be similar to the pyrolysis smoke studied earlier under laboratory conditions; the real part of the refractive index for natural smokes was noticeably lower (n ~ 1.4 - 1.5). Imaginary part of the refractive index in all cases was lower than the resolution threshold, i.e., < 0.005. Contrary to the laboratory smokes, the condensation activity (the Hanel parameter) of natural smokes was high and varied in the range 0.15-0.3, that is rather characteristic of summer aerosol. The particle size distribution in some powerful emissions on September 6-10 and September 17 was bimodal, the characteristic size of the coarse mode was r = 0.3-0.4 mkm. The condensation growth factor curve for some smokes was also bimodal with maxima at r ~ 0.2 and 0.6-0.8 mkm.