Formaldehyde as a SOA Indicator: Regional and Temporal Variability

Formaldehyde, a short-lived species, is used as an indicator of secondary organic aerosol (SOA) formation due to its involvement in the chemical reactions that produce SOA. While formaldehyde is emitted during fires, observed concentrations in regions like the Amazon are often too high to be explained solely by combustion, suggesting additional sources. Previous research has shown that during the 2010 fire season in the Amazon, SOA was found to account for 52% of total organic aerosol (OA) emissions, highlighting the importance of SOA in the region's aerosol budget.

In this study, we extend this previous work by analyzing satellite observations of formaldehyde, aerosol optical depth (AOD), and single scattering albedo (SSA) across multiple years. We examine whether higher formaldehyde concentrations, indicative of more active SOA formation, continue to correlate with higher AOD and SSA, suggesting increased SOA mass and the presence of non-absorbing aerosols.

Also, we investigate whether these relationships hold in other regions, such as Southern Africa, where SOA contributions to OA emissions were found to be lower. Additionally, we explore the temporal variability of the formaldehyde-AOD-SSA correlation, assessing whether these associations are consistent across different fire seasons and years. This analysis aims to uncover potential temporal trends in SOA formation dynamics and better understand the regional and inter-annual variability of these relationships.