During a nine-week field campaign in July 2001, an extensive suite of surface and aloft instrument platforms were deployed near Philadelphia, PA as part of the North American Research Strategy for Tropospheric Ozone-Northeast Oxidant and Particle Study (NARSTO-NE-OPS). The goals of this investigation are to better understand the relationships and conditions leading to high ozone concentrations and increased levels of fine particles; determine contributions from local and distant sources; examine the role that meteorological properties play in transport and mixing pollutant concentrations; and provide an observational database for model initialization and validation.

The authors, a team of undergraduate meteorology majors from Millersville University (MU), provided 24/7 on-site support in order to obtain aloft measurements of T, p, Rh, Wind velocity, Ozone and 2.5 micron particle concentrations, as well as surface concentrations of fine particles and criteria gases. The MU student team conducted 536 vertical profiles using a 7 cubic meter tethered balloon system, concurrent 10-hour integrated measurements and time series of PM and toxics using a 100 cubic meter tethered blimp, and surface measurements of CO, SO2, O3, and NO/NO2/NOX. Over a four-week period, several case studies were documented.

This paper describes the synoptic, regional and local scale circulations that accompanied three pollution episodes during a cooler and drier July 2001. These episodes occurred on July 10, 17, and 21-25 and represent a variety of interesting conditions that include a recirculation event, the influence of a back-door cold front, and a meandering quasi-stationary front, respectively. Emphasis is given to the measurements obtained by the MU team and the integration of those measurements into the synoptic depiction in order to construct a correlation between the large-scale condition and the concentrations observed at the site.