RETRIEVAL OF AEROSOL PROPERTIES FROM BOUNDARY-LAYER EXTINCTION MEASUREMENTS WITH A DOAS SYSTEM

Boundary layer trace gas and particulate extinction measurements in th e wavelength region from 320 nm to 680 nm have been performed by means of a differential optical absorption spectroscopy (DOAS) system at Ca pe Arkona (Island Rugen/Germany). The wavelength-dependent extinction coefficient sigma(e)(lambda) is determined from the attenuation of rad iation along two paths of different lengths. Nearly simultaneous recor ding of the concentrations of O-3 and NO2 within the same air mass all ows a correction of their contribution to sigma(e)(lambda). The extinc tion coefficients are compared with volume scattering coefficients mea sured by an open integrating nephelometer. Differences between the mea surements can be attributed to atmospheric inhomogeneities. A simplifi ed model involving monomodal log-normal distributions is applied to ap proximate the total particle surface area concentration and an upper l imit of the accumulation mode radius. This allows a rough estimate of the particle number concentration. During the summer of 1995 the mean (median) surface area concentration was about 350 (250) mu m(2)/cm(3), and the particle number concentration ranged from about 100 cm(-3) to some 1000 cm(-3).