Terrain-induced Rotor Experiment: Mountain waves, rotors, and clear-air turbulence

Fifty years after the Sierra Wave Project, and nearly thirty years after the Colorado Lee Wave program, the atmospheric science community is revisiting large-amplitude mountain waves, rotors, and associated clear-air turbulence with a coordinated field program and research effort. The goal of this effort is to improve the understanding and predictability of the coupled mountain-wave/rotor/boundary-layer system and the associated clear-air turbulence in complex terrain while taking advantage of the newest advances in remote sensing and mesoscale numerical modeling. Atmospheric rotors, intense low-level horizontal vortices that form along an axis parallel to and downstream of a mountain ridge crest, are know to pose a great hazard to aviation.

A two-phase effort is comprised of the Sierra Rotors Project (SRP; 2004), an exploratory initial phase, and the Terrain-induced Rotor Experiment (T-REX; 2006), a larger observational and research effort. Both SRP and T-REX field activities have been focused on Owens Valley and the months of March and April. Owens Valley lies to the east of the southern Sierra Nevada, which is the tallest, steepest, quasi two-dimensional topographic barrier in the contiguous United States. Mountain waves and attendant rotors are known to reach particularly striking amplitude and strength there.

In this talk we will: 1) give an overview of the ground-based and airborne, in situ and remote-sensing measurements that will be conducted both upwind and within Owens Valley during T-REX field campaign in spring 2006, and 2) present some of the results of observational data analyses and high-resolution numerical simulations of rotors and breaking gravity waves documented during the Sierra Rotors Project.