Intellectual Merit: This research will advance understanding of the potential role of aerosol pollution in modifying wintertime orographic precipitation. A key issue to be addressed is how the influence of aerosol pollution upon clouds may be altered by various synoptic weather regimes, cloud types, and amounts of supercooled water within these clouds. Based on previous modeling results, it is anticipated that clouds with higher amounts of supercooled water (such as those typically found over the San Juan Mountains of Colorado) are more susceptible to impacts by aerosol pollution. The modulation of this potential response will be addressed both temporally via time-series measurements at the Storm Peak Laboratory (SPL) and spatially through more distributed measurements over the San Juan Mountains of Colorado and through model simulations.
Potential for Transformative Research: This investigation has the potential to revise traditional theories of aerosol-induced impacts on wintertime orographic precipitation. Prior work has suggested that increased pollution aerosol concentrations lead to a significant reduction in precipitation falling from orographic clouds. Further studies by the Principal Investigators conducted in the Park Range mountains of Colorado suggest that aerosol pollution may also redistribute orographic precipitation and subsequent runoff among adjacent river basins. In this view, some reduction of total precipitation may occur but aerosol-induced shifts in the location of precipitation predominate. The relative contributions of these two potential influences will be further explored in this new study. Consideration of longer time periods (i.e., a full winter season) should lead to more robust conclusions, as well as an improved regional climatology of pollution aerosol influences.
Broader Impacts: This work has significant demographic and economic implications. If pollution aerosols are indeed systematically reducing mountain snowfall, increased development across the western U.S. will in turn reduce available snowpack-derived water resources needed to sustain such population growth and require strategies to minimize such impacts. Education and outreach activities at SPL during the field component of this study will include a three-day graduate level mesoscale modeling class led by the Principal Investigator, a week-long graduate/undergraduate class in mountain meteorology led by a University of Wisconsin collaborator, and. a graduate field meteorology class offered through the Desert Research Institute focusing on SPL's unique observational capabilities. The location of the laboratory at the summit of the Steamboat Ski Resort also affords considerable public access to its full range of activities, and the Principal Investigators supported under this grant will conduct open houses for the public and create a more permanent outdoor display describing work being done under this project.
