Variability of aerosol optical properties over Hefei during September 1993 to September 1994

An 8-wavelength sun-photometer has been operated at Hefei (31. 31°N, 117.17̈E) to monitor optical properties of atmospheric aerosols. Altogether 133 solar spectral extinction data were obtained on clear days during the period from September 1993 through September 1994. In this paper, the feature of the sun-photometer is briefly described. A relative aureole method is introduced, which can be used to monitor temporal evolution of aerosol loading during the sun-photometer calibration period. Temporal variabilities of spectral aerosol optical depths and Angstrom turbidity parameters are presented. Relation of these variabilities with synoptic and local meteorological conditions are analyzed and discussed. From measured spectral aerosol optical depths under some representative atmospheric conditions, columnar aerosol size distributions have been retrieved by a linearly constrained inversion method. These typical columnar aerosol size distributions are also presented and discussed.