A methane measurement on its own says how much is in the air, not where it came from. Three things make it say more: the wind that delivered it, the weather that trapped it, and the other gases that arrived with it. None of this requires a transport model — it is all in the observations.
Two roses from the same hours. On the left, how often the wind blows from each direction. On the right, how much methane arrives from it. If the two shapes match, you are looking at the wind; where they differ, you are looking at a source.
Several times each winter the valley fills with cold air that the wind cannot clear, and everything emitted into it stays there. These are the episodes Utah knows for its haze; methane does the same thing, invisibly. Each line is a site's own build-up, composited across every event since the record began.
Valley heat deficit is the continuous version of the same thing: the energy it would take to mix the valley out. Above about 4 MJ m−2 the valley is formally in a cold-air pool. The site 3,000 m up at Hidden Peak sits above the pool rather than in it, which is the control that makes the rest of the panel mean something.
One point per cold-air pool. If build-up were simply a matter of time, these would climb a line.
The University of Utah tower measures methane beside carbon dioxide and carbon monoxide, and the three gases leave a source in ratios that give the process away. Burning something makes CO2 and CO with almost no methane. A leaking gas main makes methane with neither. A landfill or a wastewater plant makes methane with no CO at all. So the slope of one enhancement against another is a signature.
Every hour with both gases, binned. A slope fitted through a cloud with no structure is not a signature, so this is the check on the panel above.