A detailed examination of the structure and evolution of the wintertime boundary layer was conducted from 3 January -14 February 2004 near Lancaster, PA in support of the research objectives of the Mid-Atlantic/Northeast -Visibility Union (MANE-VU). Two tethered balloons were used to deploy meteorological sensors, condensation particle counters, laser-diode scatterometers, and filter samplers to altitudes of 750 m AGL, while a suite of ground-based instruments measured trace gas and particle concentrations and meteorological parameters. January 2004 was characterized by a very active synoptic pattern that frequently brought Arctic air into the mid-Atlantic region and resulted in this being the 10th coldest January on record. Tethered balloon measurements were primarily limited to times when progressive anticyclones moved over the site, bringing clear skies, strong nocturnal radiational cooling, and relatively light boundary layer wind speeds. The measurements obtained using the single-site tethered balloons are being integrated into a regional context by incorporating surface and aloft observations from the NWS network, as well as regional profiler data and WRF and Eta model output. Laser-diode scatterometers (DustTraks), condensation particle counters (TSI CPCs), and Teflon filter samplers (PEMs) were deployed on tethered balloons, and the data then integrated with meteorological data from onboard sensors to characterize the variability of aerosol concentrations and relate it to ground-based measurements using similar instruments. It can be demonstrated that above average PM2.5 dry mass concentrations from the filter samplers analyzed at the Harvard School of Public Health are highly correlated with high DustTrak concentrations observed in the soundings when the atmospheric boundary layer was well mixed. In comparing the ground PEM data with the ground DustTrak data, total and size partitioned particle counts, black-carbon data, and scattering coefficients, it can be concluded that there is a direct relationship between the period averages of these data and meteorological events. The time periods of above average concentrations for each of these data correspond to episodes when the region was dominated by an upper level ridge in the east coupled with warm air advection into Pennsylvania. These data can be used in analyzing and interpreting the variability of aerosols and air pollutants in a wintertime boundary layer. This poster will provide a summary of significant particle events and their relationship to meteorological events. Over 20 undergraduate meteorology students from Millersville University participated in this project.