Pandora is a spectrometer Surface-level O3 is a major air pollutant that has serious threats to human health and ecosystems. Chemical transport models (CTMs) show notable biases in surface O3 across CONUS, particularly in the eastern US compared to the west. This study investigates the relationship between model biases in surface O3 and HCHO columns, HCHO vertical profiles across five regions of CONUS during the summers of 2021-2023. We use HCHO and surface O3 simulation from GEOS-CF (0.25°×0.25°), evaluated by HCHO retrievals from PGN (Pandonia Global Network) multi-axis products, and surface O3 measurement from EPA Air Quality System (AQS) network. Our findings reveal consistent model biases in surface O3 (O3,sfc) and HCHO tropospheric columns (HCHOtrop) across the five regions of CONUS, underscoring a strong connection between model biases in HCHOtrop and O3,sfc. The HCHOtrop bias appears to stem from inaccuracies in the modeled HCHO vertical profile, which significantly overestimates HCHO concentrations within PBL in the eastern US, while showing less bias in the western US due to offsetting negative biases below 500 m. During heatwaves, we find intensified model biases in O3,sfc and HCHOtrop particularly in the eastern US, largely due to a severe overestimation of HCHO around 1-2 km. This is because heatwave amplify HCHO vertical gradient between 500 m and 1.5 km in PGN, while model maintains a HCHO profile shape similar to lower temperature scenarios. Consequently, we expect that model biases in O3,sfc and HCHOTrop will increase in urban areas under future extreme heat conditions.
Tropospheric photochemistry from remote sensing & modeling