AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Refractive Index and Optical Properties of Brown Carbon Aerosols from Peat Fires
YULI W. HEINSON, Benjamin Sumlin, Nishit Shetty, Apoorva Pandey, Brent Williams, Rajan Chakrabarty, Washington University in St. Louis
Abstract Number: 183 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Peatlands are extremely large sinks of carbon on the planet and face an increasing threat of wildfires due to human action. Thus, the impact of peat fires on health and climate has become a problem of great concern in recent years. Peat fires smolder at low temperatures and spread underground, which make them long lived and difficult to extinguish. Smoldering peat fires predominately produce a class of spherical organic aerosols – brown carbon (BrC) – which have a strong absorption in the short visible wavelengths (350 – 550 nm). It has been hypothesized that these aerosols, emitted in large quantities from these fires, could have a significant impact on radiative forcing. Therefore, accurately quantifying the optical properties and refractive indices of these aerosols are necessary for inclusion in climate models and satellite retrieval algorithms. We studied the optical properties of BrC aerosols emitted from laboratory combustion of Alaskan and Indonesian peatlands with varying fuel moisture content. Four integrated photoacoustic-nephelometers (IPN) operated at wavelengths 375 nm, 405 nm, 532 nm, and 1047 nm were used to measure the absorption and scattering coefficients, and the single scattering albedo in real time. Simultaneous measurements made using a scanning mobility particle sizer (SMPS) provided the size distribution of the emitted particles. Using a custom-made inversion algorithm based on the Lorentz-Mie theory, which took as input the aforementioned measurements, we were able to retrieve the complex refractive indices of the aerosols. In this talk, we will discuss in detail our results from the suite of experiments carried out over the last year.