Mountain-Wave Evolution and Orographic Precipitation

University Of Washington, Seattle WA

Investigators

Abstract

Mountains form natural barriers to wind flow. As winds in general, and storms in particular, approach mountain ranges, mountain waves develop above and downstream of the barrier. At the same time, low-level flow may become blocked and diverted around the periphery of the mountains. These flows are often too small in scale to be accurately captured by global weather and climate models, but produce drag on the large-scale flow that must be parameterized. This research includes the training and professional development of two graduate students, including one under-represented minority. Results will be shared through journal articles and conference presentations, including webinars organized by the Mountain Meteorology Committee of the American Meteorological Society (AMS). The results of this research will also benefit water resource managers, hydrologists and those studying the current state of our climate and potential future shifts in mid-latitude storms. This study attempts to place parameterization on a firmer theoretical foundation. The large-scale responses to orographic drag will be studied through the analysis of high-resolution numerical simulations. Heavy precipitation over mountains is largely driven by the passage of large-scale weather systems. Prototypical theoretical studies of the interactions of these weather systems with idealized mountain ranges have not previously been undertaken due to the complexity of modeling large- and small-scale flows. This research builds on prior studies of multi-scale interactions in dry air flow by the inclusion of moist flow as a result of the combination of mid-latitude cyclones and more localized ascent forced by topography into vigorous updrafts and enhanced precipitation.