The Dynamics and Structure of Flow Through The Columbia River Gorge: The Results of Idealized and Case Study Simulations

The Columbia River Gorge represents an ideal natural laboratory for studying gap flow, with a relatively simple geometry, near level bottom terrain, and large numbers of observing sites along its length. This presentation will examine the essential dynamics of Columbia Gorge gap flow through detailed analysis of high-resolution (down to .4 km) MM5 simulations for both real cases and for idealized flow simulations. The later simulations use actual terrain but apply idealized flow and temperature structures approaching the gap. This paper will examine the relative importance of hydraulic and wave-related mechanisms in producing the pressure and wind fields associated with gap flow for a wide range of environmental flow situations with differing stability, flow strength and vertical wind shear. These results will be compared to several real events to confirm the fidelity of the idealized simulations and the physical conclusions derived from them.