In the winter of 2010-2011 the Persistent Cold-Air Pool Study (PCAPS) was conducted to investigate the effects of meteorology on the initiation, maintenance and dissipation of multi-day episodes of strong stability that affect the buildup of air pollutants in the Salt Lake Basin. In this paper we evaluate the effects of various meteorological factors on the evolution of stable layers and the related buildup of particulate matter with diameter less than 2.5 micrometers (PM2.5).

PM2.5 concentrations generally decreased with elevation above the Salt Lake Basin floor, as determined from a line of filter samplers running up a basin sidewall northeast of the main Salt Lake City urban area. Concentrations within the cold air pool increased as multi-day stable layers built up within the basin. For a period in January and February 2011 a linear relationship (r^2 = 0.78) was found between 24-h-average PM2.5 concentrations and bulk atmospheric stability within the basin. This relationship will be investigated further using different measures of atmospheric stability that are determined by integration to different heights above the valley floor. The investigation will focus on which method and what height integration is most closely related to measured valley floor PM2.5 concentrations, and will evaluate the results in terms of conceptual models. Other factors besides atmospheric stability affect PM2.5 concentrations in the valley. These additional factors will be discussed in the light of the atmospheric stability results and based on field experience in the wintertime experiments.