Fire diurnal variation and plume rise impacts on air quality

We analyzed the effects of the diurnal cycle of fire emissions and plume rise on U.S. air quality using MUSICAv0 (Multi-Scale Infrastructure for Chemistry and Aerosols Version 0) during the 2019 FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality) and 2018 WE-CAN (Western wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen) field campaigns. To include diurnal cycle of fire emissions in the model, we employed two approaches: a diurnal cycle of fire emissions climatology and diurnal cycle of fire emissions derived from a satellite fire radiative power product. We also implemented two sets of plume rise climatologies, and two plume rise parameterizations. We evaluated the model performance with airborne measurements, U.S. EPA Air Quality System (AQS) surface measurements, and satellite products. Overall, including plume rise improved model agreement with observations such as aircraft observations of CO and NOx for FIREX-AQ and WE-CAN. Applying diurnal cycle of fire emissions also improved model performance, such as for surface PM2.5 in fire-impacted regions. The impact of plume rise showed to be larger than the impact of diurnal cycle of fire emissions and plume rise can greatly enhance modeled long-range transport of fire-emitted pollutants. The simulations with plume rise parameterizations generally performed better than the simulations with plume rise climatologies during FIREX-AQ, but not for WE-CAN. The 2019 Williams Flats Fire case study demonstrated that diurnal cycle of fire emissions and plume rise changes fire impacts because the fire emissions are subject to different meteorology and chemistry when emitted at different times of a day and altitudes. Moreover, diurnal cycle of fire emissions and plume rise also impact local-to-regional meteorology and chemical reaction rates.