Combining Multi-Wavelength AERONET SSA Retrievals with a MIE Model to Quantify the Size of Absorbing Aerosols and the In-Situ Lifetime of Sulfate.
Abstract
Black carbon (BC), organic carbon (OC) and dust (or Absorbing Aerosols - AA) can strongly interact with solar radiation, leading to impacts on the atmospheric radiation budget, climate, water cycle, and more. This interaction critically relies on the particle size distribution, chemical composition and mixing state in-situ. Attempts have been made to elucidate particle size, mixing state, emissions, and aging over highly polluted regions in Asia using different models and methods. Most meteorology models currently used assume a non-Core-Shell approximation which in turn tends to underestimate the overall absorption profile, requiring scaling to match optical properties such as SSA and AAOD and sizer information. Consequently, these models tend to underestimate ultra-longrange transport and non-local polluted conditions, frequently induced by vertical transport and aging associated with underestimated absorption. To achieve a better understanding of AA and their impact on the atmosphere, this work uses long-term ground observations in tandem with a Mie model using a core-shell assumption to provide more detailed information about their size, magnitude, and chemical and physical properties. We employ a MIE model of core-shell coated mixtures of AA (specifically a mixture of BC core with sulfate shell (MBS) and OC core with sulfate shell (MOS)) across both UV bands which tend to absorb in contact with all small particles, and visual bands, which absorb with BC at all particle sizes. Our solution space is the merger between each individual inversion across all corresponding wavelengths, with fitting done based on the temporally varying magnitude of the measured AOD and inverted SSA incorporating all individual measurements at each station from 1997 to 2016. The aerosol properties and pollution sources of different places around Asia have been elucidated base on three idealized profiles previously made of Urban [Urban], Long-Rang Transport [LRT] and Biomass Burning [BB] sites. The results of the comparison between the LRT profile and each site are used to evaluate the aging process of particles in the atmosphere and further calculate the e-folding time of sulfate. Uncertainties in optical properties is explored using a bootstrap method. Initial results show that retrieved aerosol properties of MBS is consistent with known properties over urban areas, biomass burning areas, and those regions frequently impacted by long-range transport events. A few interesting findings are explored, including mixing between different sources, detection of otherwise missing sources, details about small particle size changes, and aging differences between BB and Urban cases. It is hoped that ongoing calculations allowing our approximation to be extended spatially away from existing AERONET measurements will also be ready to present.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.A55O1600W