Dust aerosol optical properties over North China

Abstract. Aerosol optical properties were obtained from ground-based sunphotometer data at nine observatories over North China during two periods of 1996–1998 and 2002–2003. The seasonal changes of aerosol optical depth (AOD) at five wavelengths were observed, with the highest value of AOD in spring, while the lowest in winter. Four patterns of AOD diurnal variation were obtained, of which the high value occurred in the morning, noon, evening and no remarkable change, respectively. Together with meteorological records, the characteristics of AOD during dust weather were analyzed, and the results show that it was more detailed and accurate to use AOD to depict the strength change of dust weather than to use surface visibility. Based on measurements by aerodynamic instrument for particle size distribution, a positive correlation between dust particle number concentration and Ångström turbidity coefficient β, and a negative correlation between aerosol geometric mean diameter (GMD) and wavelength exponent αwere revealed.