To analyze the effects of mixing with soot aggregates on retrieving dust properties for satellite observations in Asia

Long range transport leads mineral dusts to internally/externally mix with the ambient aerosols, such as soot particles, naturally. The physicochemical characteristics of dust particles thus are dramatically altered after mixing with soot aggregates. Therefore, the investigation on the optical properties of mineral dust along with their pathway causes a significant topic for understanding the impacts of Asian dust storm on regional air quality, environment and climate. Unfortunately, the previous researches regarding to the optical properties of dust/soot mixture for satellite remote sensing are scarce. Consequently, the objective of this study is to simulate the effects of mixing with soot aggregates on the optical properties of dust particles for satellite observations based on the well developed models. A tri-axial ellipsoidal model for dust particles by introducing the third morphological freedom to improve the symmetry of spheroids has been developed and showed in good agreement for the retrievals of dust optical properties from remote sensing measurements and ground based observations. For the model of soot aggregation, the scattering properties of fractal aggregates can be obtained with the Rayleigh-Debye-Gans (RDG), superposition T-matrix and Generalized Multiple Mie (GMM) methods. The results show that the aerosol optical depth (AOD) retrievals of dust particle will be underestimated while the single scattering albedo (SSA) will be overestimated when neglecting the combination of soot aggregates. The simulations also suggest that simultaneously retrieve AOD and SSA based on the apparent reflectance may induce large uncertainty for the dust/soot mixtures.