Investigation of methane emission sources from Indianapolis using an aircraft-based platform

Quantification of the magnitude and uncertainties of greenhouse gas emissions is important for establishing scientifically sound policies for mitigating fossil fuel emissions in urban environments. Recent studies have shown that urban city centers are significant sources of anthropogenic methane. However, urban CH₄ fluxes do not correlate with emissions from combustion sources. While the emission inventory for carbon dioxide is relatively well understood, the sources of methane are less defined because of the diverse range of sources and relatively limited observational studies of this potent greenhouse gas. Using cavity ring-down spectroscopy, flask samples, and a mass balance approach, we present initial results of our measurements of methane emissions over the city of Indianapolis using an aircraft-based platform. This investigation, which is part of the Indianapolis Flux Project (INFLUX), will help gain insight into the nature of the uncharacterized sources of methane from this urban center.