Turbulent diffusion and turbulent thermal diffusion of aerosols in stratified atmospheric flows

M. Sofiev, V. Sofieva, T. Elperin, N. Kleeorin, I. Rogachevskii, S. S. Zilitinkevich

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Abstract

The paper analyzes the phenomenon of turbulent thermal diffusion in the Earth atmosphere, its relation to the turbulent diffusion, and its potential impact on aerosol distribution. This phenomenon was predicted theoretically more than 10 years ago and detected recently in the laboratory experiments. This effect causes a nondiffusive flux of aerosols in the direction of the heat flux and results in formation of long-living aerosol layers in the vicinity of temperature inversions. We applied the theory of turbulent thermal diffusion to the Global Ozone Monitoring by Occultation of Stars (GOMOS) aerosol observations near the tropopause in order to explain the shape of aerosol vertical profiles with elevated concentrations located almost symmetrically with respect to temperature profile. We demonstrate that this theory is in good agreement with the observed profiles of aerosol concentration and temperature in the vicinity of the tropopause. In combination with the derived expression for the dependence of the turbulent thermal diffusion ratio on the turbulent diffusion, these measurements yield an independent method for determining the coefficient of turbulent diffusion at the tropopause. We also derived a practically applicable formulation for dispersion of atmospheric trace species which takes into account the phenomenon of turbulent thermal diffusion. We evaluated the impact of turbulent thermal diffusion to the lower troposphere vertical profiles of aerosol concentration by means of numerical dispersion modeling and found a regular upward forcing of aerosols with coarse particles affected more strongly than fine aerosols.

Original languageEnglish
Article numberD18209
JournalJournal of Geophysical Research
Volume114
Issue number18
DOIs
StatePublished - 1 Jan 2009

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