Mountain-Wave Evolution and Orographic Precipitation II

University Of Washington, Seattle WA

Investigators

Abstract

Mountainous terrain has a significant impact on local and regional weather conditions. The flow over mountains is known to enhance precipitation on the upslope sides, and the impact of the air rising to different levels of the atmosphere has a downstream impact on larger-scale weather patterns. However, many questions about the details remain. This award provides funding for a researcher and two graduate students to study topics related to atmospheric interactions with mountain topography. In addition to the training of the next generation of scientists, this award will have a broad societal impact through the potential to improve weather forecasts. The two main thrusts of the work are on improving understanding of: 1) the dynamics and predictability of multi-scale orographic precipitation and 2) mountain waves and their feedback on the synoptic-scale flow. The orographic precipitation work would be conducted using idealized modeling. The research team will investigate the relative contributions of dynamics and microphysics toward increasing precipitation by diagnosing those processes in scenarios with and without mountains and cyclones using the Weather Research and Forecasting (WRF) numerical model. Additional work will be conducted using cases with different background static stabilities, moisture fluxes, and ridge positions. The orographic precipitation component will also include work on mesoscale predictability as the researchers hypothesize that small perturbations to the large-scale flow will generate large perturbations to the precipitation patterns associated with mesoscale terrain features. The mountain wave work would use modeling, theory, and observations from prior field campaigns to address how gravity-wave-drag influences nontrivial large-scale flows and under what conditions nonlinear processes strongly regulate the amplitude of mountain waves. 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.