Local and Regional Enhancements of CH ₄, CO, and CO ₂ Inferred from TCCON Column Measurements

In this study, we demonstrate the utility of available correlative measurements of carbon species to identify regional and local airmass characteristics and their associated source types. In particular, we combine different regression techniques and enhancement ratio algorithms with CO, CO ₂, and CH ₄ data of total column abundance from 11 sites of the Total Carbon Column Observing Network (TCCON) to infer relative contributions of regional and local sources to each of these sites. The enhancement ratios provide a viable alternative to univariate measures of relationships between the trace gases that are insufficient in capturing source type and transport signatures. Regional enhancements are estimated from the difference between bivariate regressions across a specific time window of observed total abundance of these species (BEHr) and inferred anomalies (AERr) associated with a site-specific background. Since BEHr and AERr represent the bulk and local species enhancement ratio, respectively, its difference simply represents the site-specific regional component of these ratios. We can then compare these enhancements for CO ₂ and CH ₄ with CO to differentiate combustion versus non-combustion associated airmasses. Our results show that while the regional and local influences in enhancements vary across sites, dominant characteristics are found to be consistent with previous studies over these sites and with bottom-up anthropogenic and fire emission inventories. The site in Pasadena shows a dominant local influence (>60 %) across all species enhancement ratios, which appear to come from a mixture of biospheric and combustion activities. In contrast, Anmyeondo shows more regionally influenced (>60 %) air masses associated with high temperature and/or biofuel combustion activities. Ascension appears to only show a large regional influence (>80 %) on CO/CO ₂ and CO/CH ₄ which is indicative of transported and combustion-related CO from nearby African region, consistent with sharp rise in column CO (3.51±0.43 % ppb/year) in this site. These methods have important application to source analysis using space-borne column retrievals of these species.