Brown carbon and black carbon in megacity smogs
G.I. Gorchakov1, A.V. Karpov1, A.V. Vasiliev2, I.A. Gorchakova1
1A.M. Obukhov Institute of Atmospheric Physics Russian Academy of Sciences, Pyzhevsky per., 3, 119017, Moscow, Russia
2Saint Petersburg State University, 1, Ulyanovskaya str., Petrodvorets, St. Petersburg, 198504, Russia
Keywords: смоги мегаполисов, коричневый углерод, черный углерод, коэффициент преломления, аэрозольная оптическая толщина, альбедо однократного рассеяния, megacity smogs, brown carbon, black carbon, refraction coefficient, aerosol optical depth, single scattering albedo
Abstract
Aerosol radiative characteristic variability stipulated by brown carbon and black carbon content variations in megacity smogs for Beijing, San-Paulu, Santiago, and Mexico have been analyzed by AERONET data. It is shown that the brown carbon contribution into the imaginary part of the refraction coefficient for a wavelength of 440 nm in smogs can exceed the black carbon contribution more than threefold. In megacity smogs the spectral dependencies of the aerosol optical depth absorption can be approximated by power function with satisfactory precision excluding some Beijing smogs at wavelength of 400 nm when relative concentration of the brown carbon is big. It is shown, that the coarse mode contribution into total aerosol optical depth extinction in smogs can constitute from 6 to 20% for wavelength of 440 and 1020 nm respectively and contribution into aerosol optical depth absorption - from 22% for wavelength of 440 nm to 38% for a wavelength of 1020 nm. The megacity smog aerosol distinguishes from the smoke aerosol formed during large-scale fires in the boreal forests of Russia by increased contribution of the coarse mode in total volume of the aerosol and high values of the imaginary part of the refraction coefficient and therefore by more greater values of aerosol absorbing ability.
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