Orography has a dramatic influence on lake-effect snowstorms, not only in regions with major mountain barriers such as the Great Salt Lake Basin of northern Utah, but also in the eastern United States and Canada where more modest relief is found around the Great Lakes. For example, over the Tug Hill Plateau of northern New York, which lies downstream of Lake Ontario, annual snowfall increases 25-50 mm for every 100 m rise in elevation and storm-total accumulations have reached 360 cm in extreme lake-effect events. Orography also modifies the morphology of lake-effect snowstorms by altering the relationship between the large-scale flow and the development of precipitation structures such as broad-area precipitation shields and shoreline bands. Knowledge of lake-orographic precipitation processes is important not only for weather prediction, but also applications in hydrology, ecology, and geomorphology. The primary goal of the project is to improve understanding of lake-orographic precipitation processes and their influence on the weather and climate of lake-effect regions. Key questions to be investigated include: (1) to what extent does orography modify the morphology of lake-effect snowstorms, (2) which orographic processes and phenomena are responsible for these modifications, and (3) to what degree do lake-orographic precipitation processes contribute to the hydroclimate of lake effect regions? These questions will be addressed in a three year research program that examines two regions where there are strong orographic influences on lake-effect precipitation. The first is the Great Salt Lake basin of northern Utah where the Wasatch Mountains and other ranges rise up to 2000 m above lake level. The second is the Tug Hill Plateau of northern New York, which provides a broad upland region 400-500 m above Lake Ontario. The research will produce a synthesis of results from a radar-based climatology, a field campaign, and numerical modeling. Intellectual merit: The research will advance knowledge and understanding of the physical processes that control lake-effect and orographic precipitation and, in turn, the influence of these processes on the hydrometeorology of lake-effect regions. Efforts to establish a relationship between the large-scale flow and lake-effect morphology have proven challenging, with previous workers specifically identifying the need to better understand the role of orography in altering structural transition zones. Project results will address this need. Broader impacts: The project addresses the societal need to improve weather and climate prediction in lake-effect regions. Other broader impacts include: (1) the infusion of research findings into undergraduate and graduate courses, training courses, and web-based educational modules, (2) the mentoring of two graduate students and the broadening of the participation of women in NSF-sponsored programs, and (3) the enhancement of public scientific understanding through collaborations with an NSF GK-12 graduate fellowship program that involve graduate student researchers in K-12 classrooms to teach discovery based environmental science in Salt Lake City school districts. Further, this research program will likely engender broad scientific interest in other allied research communities such as hydrology, ecology, and geomorphology.
Orographic Influences on Lake-Effect Precipitation