"City – background” difference in diagrams of relation of the scattering coefficient and the Black Carbon fraction in the near-surface aerosol for different types of aerosol weather

Abstract

The characteristics of aerosol scattering and absorption by the particulate dry basis were measured at the Aerosol Station of IAO SB RAS and the Fonovaya Observatory in 2014-2018. The measured results were used to analyze the variability of diagrams of relation of the scattering coefficient σd and the Black Carbon fraction Рd for the near-surface submicron aerosol. Average values of the parameters for every season and different types of aerosol weather were estimated. In the diagram, the types of aerosol weather are characterized by different relations of the scattering and absorbing properties of aerosol: smog (σd>100Mm-1, Рd>0.05), smoke haze (σd>100 Mm-1, Рd 0.05). Common and distinctive features of the diagrams for the suburban and background conditions were revealed. It was shown that the haze and background types are the main contributors to the measurement statistics. For the haze, the maximal diurnal average values of the parameter of particle absorption at the Fonovaya Observatory, in comparison with the suburban area, decrease from Рd ∼0.23 (particle absorption index χ∼0.138) to Рd ∼0.13 (χ∼0.078). For the background and haze types of aerosol weather, the smallest values of the scattering coefficient (as low as ∼2Mm-1), which were five times smaller than those observed under suburban conditions, were achieved at the Fonovaya Observatory. No smog situations were observed at the Fonovaya Observatory in the spring, summer, and fall seasons. The statistical significance of difference in values of aerosol characteristics between the both measurement sites was assessed. The significant difference between the average values of parameters was observed for winter smog, background, and haze.