Size distribution of near-surface aerosols and its relation to the columnar aerosol optical depths

Simultaneous data on Aerosol Optical Depth (AOD) and size segregated, near-surface, aerosol mass concentration was obtained from a Multi wavelength Solar Radiometer (MWR) and Quartz Crystal Microbalance Impactor (QCM), respectively. These were used to examine the association between near-surface aerosol properties and columnar AOD. The spectral AODs were approximated to the Ångström relation τp=βλ-α, and the wavelength exponent α and turbidity coefficient β have been obtained. In general, α was found to be well associated with the relative abundance of accumulation mode aerosols (estimated from the simultaneous QCM data) while β followed the variations of the coarse mode aerosol mass concentration; the association being closer during periods of continental airmass.