On the relation between haze layer and air mass aerosol at an urban location — case studies

Abstract Aerosol extinction spectra of the lowest part of the urban boundary layer at Leipzig measured by means of sunphotometers in the wavelength range between 0.36 μm and 1.05 μm are presented. The temporal behaviour of these spectra is compared with that of relevant atmospheric turbidity parameters. Special attention is paid to the analysis of atmospheric aerosol optical thickness spectra. It is shown that, concerning aerosol properties, the ageing of an air mass caused by urban activities is identical with an increase of aerosol optical thickness, especially in the short-wavelength-range. This fact could be attributed to the convective rise of, primarily, small aerosol particles ( r μ m) being emitted by anthropogenic sources near the ground. This process also seems to be responsible for a vertical aerosol stratification within the haze layer. It was found that in the case of turbulent mixing the optical state of the around layer is mainly determined by accumulation and coarse mode particles, whereas the upper layers contain a large amount of fine particles.

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