Extended Abstract (1.2M)15.2
Simulations of rotors using steep lee-slope topography
Rolf F. Hertenstein, Colorado Research Associates, Boulder, CO; and J. Kuettner
High-resolution, two-dimensional simulations were performed using the Regional Atmospheric Modeling System (RAMS) with topography representing the lee slope of the Sierra Nevada mountains. The model was initialized with soundings derived from observations during the 1950's Sierra Wave Project (SWP). Agreement between simulations and observations taken during the SWP are encouraging. Flows resembling a hydraulic jump show very turbulent rotors inside the jump, extending in a turbulent wake more than 50 km downstream. The nature of this rotor flow is characterized by excessive shear between tight vertical currents of more than +/- 20 m/s. The rotor resembles the flow pattern encountered during the SWP when one of its research sailplanes was destroyed in flight. This type of flow is substantially different from the more common turbulent, yet quasi-organized, rotor circulation associated with resonant lee-waves.
Sensitivity studies of various initial wind and stability profiles were performed. Flow characteristics were found to be surprisingly sensitive to small changes in the initial profiles, e.g., to details in the vertical wind profile. Further sensitivites, e.g., to the presence of deep upstream cloud cover ("cap cloud") are currently being investigated. Some thoughts on the nature of hydraulic jumps vs. breaking waves will be discussed.
Session 15, Rotors
Thursday, 20 June 2002, 1:30 PM-2:45 PM
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