Evolution of Ammonia (NH3) and Peroxyacyl Nitrates (PANs) in Wildfire Smoke Plumes from Space

Biomass burning is one of the largest natural sources of gas-phase ammonia (NH₃) to the atmosphere and this has implications for secondary aerosol formation. We use measurements of NH₃, peroxyacyl nitrates (PANs), and carbon monoxide (CO) from the Cross-track Infrared Sounder (CrIS) aboard the Suomi-National Polar orbiting Partnership (S-NPP) satellite to investigate the relative concentrations and evolution of these species in aged smoke plumes. Our analysis focuses on wildfires over the western United States during the 2018 fire season, a period that coincides with the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) aircraft campaign. We calculate normalized excess mixing ratios (NEMR) of NH₃ and PANs with respect to CO in smoke plumes from fires to document and understand the evolution of NH₃ and PANs as these plumes are transported downwind.