September 1st 2016 mass-balance flight. Panel A shows time traces for measured CH4 and altitude. Panel B shows a map of the mass balance flight, with data points colored and sized by methane concentration. A dotted arrow is drawn along the dominant wind direction (300°), with measured wind (white barbs) also shown along the flight path. Reference points labeled 1 through 16 are shown in both panels, and are used to define cross-sections (blue lines, Panel B). DOI: https://doi.org/10.1525/elementa.308.f5