Extracting and Modeling Aerosol Optical Properties Using TEM Imaging and RDG Theory

Abstract:

Aerosol are a suspension of solid or liquid particles in the air, such as dust or haze. They impact the atmosphere radiation balance by absorbing and re-emitting or scattering electromagnetic radiation. Aerosols also have been linked to climate change, severe storms, and altering cloud morphology and precipitation. There is still uncertainty to the extent of cooling or warming caused by aerosol due to uncertainty in measuring aerosol optical properties. The refractive index of aerosol is a key optical parameter which is also influenced by aerosol morphology. Biomass burning aerosol (BB) are produced by burning a sample of wood in a tube furnace and introduced into a smog chamber. Fresh and aged aerosol samples are collected on filters from the chamber and imaged using TEM. ImageJ and MATLAB were used in tandem to measure the aerosol particle’s maximum length, average monomer radius, and fractal dimension. The extinction and scattering cross-sections of the were measured in the laboratory using a cavity ring down spectroscopy and nephelometry. The Raleigh-Debye-Gans Approximation (RDGA is used to fit the experimental cross section to model predictions to extract refractive indices of the aerosol.

We acknowledge the support from the national Science Foundation grant number NSF #1936961