ON THE RELATION BETWEEN HAZE LAYER AND AIR-MASS AEROSOL AT AN URBAN LOCATION - CASE-STUDIES

Aerosol extinction spectra of the lowest part of the urban boundary la yer at Leipzig measured by means of sunphotometers in the wavelength r ange between 0.36 mu m and 1.05 mu m are presented. The temporal behav iour of these spectra is compared with that of relevant atmospheric tu rbidity parameters. Special attention is paid to the analysis of atmos pheric aerosol optical thickness spectra. It is shown that, concerning aerosol properties, the ageing of an air mass caused by urban activit ies is identical with an increase of aerosol optical thickness, especi ally in the short wavelength-range. This fact could be attributed to t he convective rise of, primarily, small aerosol particles (r < 0.3 mu m) being emitted by anthropogenic sources near the ground: This proces s also seems to be responsible for a vertical aerosol stratification w ithin the haze layer. It was found that in the case of turbulent mixin g the optical state of the ground layer is mainly determined by accumu lation and coarse mode particles, whereas the upper layers contain a l arge amount of fine particles.