1) The document analyzes two cases of elevated free tropospheric ozone in Houston during September 2013 using ozonesonde data - a stratosphere-troposphere exchange event from September 21-25 (Case 1) and a thunderstorm on September 5th with potential lightning-produced ozone (Case 2). 2) Case 1 showed strong stratospheric intrusions into the free troposphere, evidenced by high potential vorticity and very low humidity. Case 2 found that while biomass burning smoke was present, the enhanced ozone was most likely from coronal discharge lightning producing over a billion molecules of ozone. 3) Lightning data was used to calculate a lightning-induced ozone