These graphs show data collected using the SOAR Cheyenne II aircraft during a flight downwind and upwind of the Houston, TX area. Calculated backtrajectories are represented by the five yellow lines that terminate along the blue leg of the flight track. The line colors used in the top graph showing measured CCN concentration at 0.5% reflect the position along the flight track shown on the map. CCN concentrations immediately downwind of Houston were observed to be as much as 10 times higher than that measured on the east, west, and south sides of the urban plume. The cause of the bimodality in concentration is not known, although similar observations were made during the TexAQS study in 2000. Aerosol size distributions measured using a differential mobility analyzer are shown in the seven numbered graphs. The position of the aircraft during each these measurements is identified by the corresponding numbers along the flight track. Both number and volume distributions are shown in each graph. Total aerosol concentration was substantially greater within the Houston plume than outside of it, while total aerosol volume concentration differed by only about a factor of two. These data suggest Houston emissions may have a pronounced impact on CCN concentrations even when measures of an aerosol that are especially sensitive to larger particles such as total mass concentration are largely unaffected.