Missoula 2020 wildfire air quality observations and model simulations supporting: Characterizing emissions, chemistry, and health impacts of aged wildfire smoke in a western US city

This dataset provides hourly air quality observations and corresponding atmospheric chemistry model simulations for Missoula, Montana during the September 2020 wildfire season. The data were developed to support analyses of wildfire smoke emissions, chemical evolution, secondary pollutant formation (e.g., ozone and secondary organic aerosol), and exposure- and health-relevant metrics. The observational dataset includes hourly measurements of criteria pollutants (e.g., PM₂.₅, O₃, NOₓ, CO), a wide range of volatile organic compounds (VOCs), oxygenated VOCs (OVOCs), hazardous air pollutants (HAPs), aerosol optical properties, and meteorological parameters. Measurements are reported in local Mountain Daylight Time (MDT). The model dataset consists of hourly model-simulated concentrations extracted for Missoula under three emission scenarios: (1) a baseline wildfire-emissions simulation (GFAS), (2) a sensitivity simulation with wildfire emissions scaled by a factor of three (3×GFAS), and (3) a no-biomass-burning simulation (NoBB). Model outputs include gas-phase species, oxidant proxies, aerosol components, secondary organic aerosol tracers, and summary metrics (e.g., total VOC and HAP-like indicators), designed to be directly comparable with the observational dataset. These datasets support the manuscript “Characterizing emissions, chemistry, and health impacts of aged wildfire smoke in a western US city,” submitted to *Atmospheric Chemistry and Physics*. Separate README files are provided for the observational and model datasets, describing variables, units, data quality, and usage notes.