Orographic precipitation refers to rain and snow that develops due to air that is forced upward over mountainous terrain. Orographic precipitation depends on numerous factors, and how those factors change in future climate states will impact the climatology of the amount and location of precipitation in relation to the terrain. One common result from climate modeling is that precipitation on the downslope side of mountains will increase, which would have a large impact on water resources and potential flooding. This study will analyze an existing high-resolution numerical simulation and perform new simulations to determine the physical mechanisms behind these changes. The work has direct impact on farmers, water-resource managers, and other stakeholders in the Western US, and the researchers will engage with this group through the participation in the Climate Impacts Research Consortium. Multiple graduate students will also be trained.
The research team will conduct a numerical modeling study to better understand the potential changes in orographic precipitation in future climate states. Prior modeling has provided evidence that precipitation will increase in the ?rain shadow? areas on the lee side of mountainous terrain. The research team will analyze existing output from a 35-year high-resolution ?pseudo-global warming? simulation and conduct new simulations to address the following research questions: 1) What types of storms contribute most to the pattern of precipitation change in the Cascades and Sierra Nevada? 2) What mechanisms ? dynamic, thermodynamic, and/or microphysical ? contribute to orographic precipitation change, and what is their relative importance? 3) How sensitive are the results to differences in model parameterizations, especially related to cloud microphysics? 4) Does the pattern and mechanisms of precipitation change in the Cascades and Sierra Nevada hold lessons for other midlatitude mountain ranges, such as the Andes or Southern Alps?
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
