As part of the Texas Air Quality Study (TexAQS) II (2005 – 2006), ozonesondes were launched from the campus of Rice University and the University of Houston providing profiles of ozone, temperature, humidity, pressure, wind speed, and wind direction. Most launches occurred in early afternoon to provide measurements during the peak of the surface ozone diurnal pollution cycle. When ozone pollution was forecast to exceed Environmental Protection Agency air quality levels, however, additional sondes were launched just after dawn to capture the residual layer containing ozone from the previous day. This study examines the impact of the residual layer ozone on afternoon ozone concentrations using data from the twelve occasions during TexAQS II on which ozonesondes were launched multiple times.