Development of a multiple solution mixing mechanism based aerosol component retrieval method for polarimetric satellite measurements

Abstract

Aerosols chemical components from different sources significantly affect climate change and air quality. In this study, we developed a satellite-based aerosol component retrieval method based on multiple solution mixing mechanism (MSMM) to extract global aerosol component from POLDER polarimetric satellite observations from 2008 to 2012. The MSMM calculates the complex refractive index using the Lorentz-Lorenz relation and constrains the solute fraction with κ-Köhler theory to retrieve the following components: black carbon (BC), ammonium nitrate-like inorganic salts (AN), dust (DU), sea salt (SS), water-soluble organic matter (WSOM), water-insoluble organic matter (WIOM), and aerosol water content (AW). By analyzing the spatial distribution and seasonal characteristics of the seven aerosol components over a five-year period, we captured the significant patterns of each aerosol component over global anthropogenic and natural hotspot emission regions. The five-year average and the seasonal patterns of each component during 2008 show significant changes, consistent with our expectations and previous studies. The pattern of global brown carbon (BrC), which is estimated by the possible tracer substances, is correlated with the fire radiative power. After analyzing the time series changes of each component in different regions for five years, we fine that the fine-mode fraction of aerosol component mass concentration in the central-eastern region of China declined about 6.05% from 2008 to 2010, which is closely related to the strong implementation of environmental protection policies. Also, we find the global aerosol component mass fraction in 2012 shows anomalies, especially a significant increase in the AW component, which is explained by the high frequency of extreme weather. The aerosol components retrieved by the MSMM are comparable with MERRA-2, with the correlations up to 0.94 for BC and 0.88 for DU in representative regions. More comprehensive species of aerosol components can be obtained using the MSMM method than MERRA-2, which can be applied to future satellite observations with higher spatial resolution.