Physical, chemical and radiative properties of aerosols in Sydney, Australia

Atmospheric aerosols are one of the most spatially variable components of the earth’s atmosphere, and so require monitoring at a wide range of sites across the globe. We have been monitoring aerosol properties in Sydney for five years, studying both spectral optical thickness, and aerosol chemistry. So far we have analysed two years of these data, and have extracted typical (seasonal average) size distributions and refractive indices. Seasonal variability was found to be weak. We have constructed a model of Sydney aerosols, consistent with our observations, consisting of a mixture of continental aerosol and soot. Using this model we have computed the direct forcing, and the lower tropospheric flux divergence produced by Sydney aerosols. Due to the high soot content, we find that the forcing is actually reduced, while the flux divergence is significantly enhanced, when compared to ‘clean’ aerosol.