The Sensitivity of Salt Lake Valley Persistent Cold Air Pools to Surface State

The Persistent Cold Air Pool Study (PCAPS) was conducted in the Salt Lake Valley between 1 December 2010 - 7 February 2011 with the goal of improving scientific understanding of the detailed meteorological factors influencing wintertime poor air quality episodes in urban mountain basins. In this study, observations and numerical modeling of persistent cold air pools (CAPs) are used to better understand the interactions between surface state, thermally-driven flows, cloud cover, and stability within CAPs. The observed characteristics and evolution of cool season Great Salt Lake breezes (in contrast to the more widely studied summertime case) and their impact on pollutant transport and stability within CAPs are documented. Numerical sensitivity simulations are used to quantify the impact of variations in land use, snow cover, and Great Salt Lake temperature on thermally-driven flows, boundary-layer stability, and fog during persistent CAPs. Finally, we discuss shortcomings in the ability of current numerical models to simulate CAPs, compare the accuracy of large-eddy versus mesoscale numerical simulations, and validate simulated CAP wind, moisture, and temperature profiles against extensive observational data.