Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7846306 | Journal of Quantitative Spectroscopy and Radiative Transfer | 2018 | 7 Pages |
Abstract
Constraining the complex refractive indices, optical properties and size of brown carbon (BrC) aerosols is a vital endeavor for improving climate models and satellite retrieval algorithms. Smoldering wildfires are the largest source of primary BrC, and fuel parameters such as moisture content, source depth, geographic origin, and fuel packing density could influence the properties of the emitted aerosol. We measured in situ spectral (375-1047â¯nm) optical properties of BrC aerosols emitted from smoldering combustion of Boreal and Indonesian peatlands across a range of these fuel parameters. Inverse Lorenz-Mie algorithms used these optical measurements along with simultaneously measured particle size distributions to retrieve the aerosol complex refractive indices (mâ¯=â¯nâ¯+â¯iκ). Our results show that the real part n is constrained between 1.5 and 1.7 with no obvious functionality in wavelength (λ), moisture content, source depth, or geographic origin. With increasing λ from 375 to 532â¯nm, κ decreased from 0.014 to 0.003, with corresponding increase in single scattering albedo (SSA) from 0.93 to 0.99. The spectral variability of κ follows the Kramers-Kronig dispersion relation for a damped harmonic oscillator. For λâ¯â¥â¯532â¯nm, both κ and SSA showed no spectral dependency. We discuss differences between this study and previous work. The imaginary part κ was sensitive to changes in FPD, and we hypothesize mechanisms that might help explain this observation.
Related Topics
Physical Sciences and Engineering
Chemistry
Spectroscopy
Authors
Benjamin J. Sumlin, Yuli W. Heinson, Nishit Shetty, Apoorva Pandey, Robert S. Pattison, Stephen Baker, Wei Min Hao, Rajan K. Chakrabarty,