Overview of Aerosol Optical Property Observations from Wildfires during WE-CAN

The net radiative impact of aerosol emissions from wildfires remains a significant uncertainty in regional and global climate models. One important source of uncertainty is aerosol radiative properties. The Western wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) was conducted on the NCAR C-130 aircraft in summer 2018, a very active fire season. The project included detailed observations of over 15 distinct wildfire plumes from a wide range of fuels combusted at different efficiencies in the Western U.S. Additionally, observations were made of highly-aged smoke from a mix of different fires. Aerosol optical properties were measured by multiple different instruments including a photoacoustic absorption spectrometer, a particle into liquid sampler connected to an absorption spectrometer, a single particle soot photometer and a CAPS extinction and scattering spectrometer. Based on detailed analysis of this extensive combined dataset, we have developed robust conclusions about the magnitude and longevity of: 1.) brown carbon absorption, 2.) absorption enhancement of black carbon caused by coatings and 3.) the wavelength resolved impact of absorbing organic carbon. Behavior of fires across the study domain is similar for many of these parameters and a consistent set of parameters have been developed that broadly represent emissions from Western U.S. fires. While these parameters broadly describe all the observed fires, details of the impact of aging and unique observations of given fires will also be addressed.