Experimental flight path on 12 July 2011 as a function of height above the ground.
Prevailing winds were from the northwest with an average magnitude of 4 m s-1. Also shown in the figure are the sites of CH4 sources within and just outside Indianapolis (black outline): Southside Landfill (SSLF), Belmont wastewater treatment plant (WWTP), Southport WWTP, and a landfill designated as TBLF. For reference, we also include the location of the Indianapolis international airport (KIND) as well as the network of 12 INFLUX tower sites. The dark green outline represents the major highway arteries traversing Indianapolis (I-65, I-70, and IN-465).