Exploring variability in CO2 and CO measurements due to episodic emissions in the Los Angeles Megacity

Measurements of greenhouse gases in cities are critical for understanding the drivers of carbon emissions. Urban areas, such as the Los Angeles (LA) Megacity represent significant sources of anthropogenic fossil fuel carbon dioxide (CO₂) emissions. Carbon monoxide (CO) has been commonly used as a tracer for fossil fuel CO₂ because it is co-emitted during the incomplete combustion of fossil fuels. Atmospheric CO₂ and CO emissions can also result from episodic emissions sources, such as wildfires. Therefore, it is important to identify whether atmospheric observations in urban areas have been influenced by local, episodic emissions sources such as wildfires given that these events would complicate attribution of CO₂ emissions if they are not included in atmospheric models. In this study, we will examine the spatial and temporal variability in CO₂ and CO atmospheric mixing ratios measured at surface monitoring stations located in and around the Los Angeles basin. We will investigate the extent to which variability in the urban enhancements or "excess" values of CO and CO₂ relative to background may be impacted by episodic emissions sources such as wildfires or flared emissions from refineries. For wildfire events, we will cross-reference the results with a fire database from CalFire, which reports all fire incidents in California. For flaring events, we will cross-reference the atmospheric CO₂ and CO observations with a database of flare activity reports from refineries located in the South Coast Air Basin. Comparing these known episodic emissions spikes with surface monitor data will help improve our understanding of the relative importance of these events for studying urban greenhouse gas emissions.