Characterizing Aerosol Emissions from Wildfires in the Western US

Wildfires are a major contributor to accumulation mode aerosol, especially carbonaceous and light absorbing aerosol, in the western United States during the summer months. These emissions not only greatly increase local aerosol mass concentrations but can also be transported over long distances, leading to regionally elevated aerosol loadings. Because of their high concentrations and radiative properties, these emissions have a large impact on both global radiation budgets and local visibility reduction, and also significantly impact cloud and precipitation formation by increasing the number of available cloud nuclei. To better understand the aerosol emissions, both primary and secondary, from these fires the NSF/NCAR C-130 aircraft was instrumented to sample wildfire plumes in the northwestern US during the peak of fire season as part of the Western Wildfire Experiment for Cloud Chemistry, Aerosol, Absorption and Nitrogen (WE-CAN). A large suite of gas and aerosol measurements characterized the emissions near sources and as a function of aging downwind of the fires. Here we present aerosol size distributions measured by a Nano Scanning Mobility Particle Sizer (NSMPS) as well as organic carbon concentrations measured by an Aerosol Mass Spectrometer (AMS), refractory black carbon (rBC) mass and number concentrations measured with a Single Particle Soot Photometer (SP2) and concentrations of Cloud Condensation Nuclei (CCN) at different supersaturations measured with a CCN counter. These measurements will characterize aerosol emissions, properties and variability relevant to understanding wildfire impacts on radiative balance, visibility reduction and cloud formation.