The Hawaiian Islands, which present a variety of terrain heights and configurations embedded within a synoptically- and interannually-modulated trade wind regime, constitute a natural laboratory for high-resolution studies of orographic flow and precipitation processes at subtropical latitudes. A combination of careful reanalysis of nearly 10 years of archived high-resolution (1.5- and 3.0-km island-scale) numerical forecasts generated using the MM5/LSM (the paired Penn State/NCAR mesoscale/land-surface model) and WRF (Weather Research & Forecasting model) and select re-runs will be used to explore a variety of questions including but not limited to: (1) Why is Mount Wai'ale'ale (1598 m MSL) on Kauai one of the wettest spots on earth?; (2) What physical processes are responsible for a lee-side summer rainfall maximum on Kona?; (3) what dynamics control diurnal and seasonal variations in strong channel winds in the zone separating Hawaii and Maui?; (4) How does reverse flow in the wake of relatively lower barriers such as Oahu depend on trade-wind properties?; (5) How do El Nino-induced modulations affect the micro-climates of zones both above and below the trade-wind inversion across the Hawaiian archipelago?; and (6) What specific conditions favor development of trapped mountain lee waves in this region?
The intellectual merit of this research rests on extension of model-based representations and associated dynamical understanding of island-atmosphere interactions across the Hawaiian archipelago to finer scales than has heretofore been possible, and within a zone where El Nino/Southern Oscillation-induced impacts are both sizable yet incompletely characterized. Broader impacts will include graduate student training but extend to improved understanding of conditions impacting commerce and transportation, fragile marine and terrestrial ecosystems, and capacity for renewable energy generation.
