During the period 30 June to 4 July 2002, several instruments of the NEOPS-DEP project were used to characterize the evolution of an air pollution episode from a site in Philadelphia. The Raman lidar and Radar/RASS profiler from Penn State University and the tethersonde instruments of Millersville University obtained high resolution measurements of the meteorological and atmospheric parameters. The episode persisted for several days and ozone levels exceeded 100 ppb for extended periods on three days. The measurements emphasized the development of a 3-dimensional representation of the air mass using the lidar, radar and sonde measurements to provide vertical profiles of the ozone, particulate matter, water vapor, temperature, optical extinction and wind velocity. The results are used to described the high temporal and spatial characteristics of the episode. One of the features observed was the rapid rise in surface ozone concentrations that occurred at mid-morning on 2 July due to the rapid mixing to the surface from an ozone storage/transport layer aloft.