The sensitivity of valley boundary layer structure and thermally driven mountain flows to land cover change

As urban populations in the United States grow, it is becoming more important to understand the impacts of anthropogenic land cover change on local weather and air quality. Changes to surface temperatures and pollutant concentrations have consequences for human and environmental health. In this study, the structure and evolution of the daytime boundary layer and surface winds in the Salt Lake Valley were examined for the case of Intensive Observing Period (IOP) 6 during the Vertical Transport and Mixing Experiment (VTMX), a period with clear skies and light upper-level winds. The Pennsylvania State University - National Center for Atmospheric Research fifth generation Mesoscale Model (MM5) was used to simulate the case, and sensitivity studies were conducted in order to evaluate the effects of land cover changes. Particular attention was paid to several features, including differential boundary layer growth across land cover boundaries, complex interactions between lake, slope, valley, and urban breezes, and a decrease in mid-valley boundary layer depth with the passage of the lake breeze front in the afternoon. The timing and intensity of these features were affected by the land cover specification, and the mechanisms responsible for these changes were diagnosed with the MM5 output.