Recent decades saw increasing wildfire activities in the western US. The annual burned area has increased by more than a factor of three over California from 1985 to 2021. While the impacts of wildfires on particulate matter air quality are well known, the extent to which biomass burning emissions affect gas air pollutants, such as O3 and its precursors, is less clear. This project will explore how wildfire emissions, when mixed with anthropogenic emissions, affect the O3-NOx-volatile organic compounds (VOC) chemistry over downwind urban areas in California. The proposed study will use emerging new-generation satellite observations (TROPOspheric Monitoring Instrument (TROPOMI), Cross-track Infrared Sounder (CrIS), Moderate Resolution Imaging Spectroradiometer (MODIS)), in situ measurements from recent field campaigns (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption And Nitrogen (WE-CAN) and Fire Influence on Regional to Global Environments and Air Quality(FIREX-AQ)) and ground-based monitoring networks, a hierarchy of models from simple box model to meteorology-chemistry model, to track the evolution O3 precursors (NOx and VOCs) from fires, investigate the radiative and chemical effects of fire smoke on O3 chemistry, and analyze their variations with fire (i.e., fuel type, fire intensity, injection height, combustion efficiency).