Understanding Tropospheric Ozone from U.S. Wildfires: Observations and Modeling

Biomass burning is an important source of chemical precursors of tropospheric ozone, which can harm human health and economic welfare. However, ozone evolution in smoke plumes is poorly understood due to complex fire emissions, coupled dynamical/chemical processes, and limited ozone observations, especially the lack of vertical ozone profiles measurements. As one of the six stations of the Tropospheric Ozone Lidar Network (TOLNet), the ozone lidar at the University of Alabama in Huntsville (UAH) measures vertical ozone profiles between 0.1 and ~12km with 2 or 10 min temporal resolution and a variable vertical spatial resolution between 150 and 750m. Such measurements can fill the gap between satellite and surface observations on wildfire events and benefit the air-quality community. In our study, we combined the ozone Differential Absorption Lidar (DIAL) and ozonesondes with other aerosol measurements to capture the vertical structure of ozone and aerosol in the downwind area of wildfires. In addition, to improve our understanding of the smoke plume transport and photochemical processes, we performed a Weather Research and Forecasting with Chemistry (WRF-Chem) simulation to quantitatively attribute the ozone production to smoke produced from wildfires. Fire emissions, anthropogenic emissions, and biogenic emissions comprise the chemical inputs. The preliminary results suggest long-range transport of ozone from the 2013 Western US Wildfires and low ozone-formation in the 2016 Southeastern US Wildfires. The vertical ozone structures (e.g., ozone laminae) were well captured by the ozone lidar and ozonesondes, while the finer structures could pose challenges in accurately modeling these wildfire events.