The Terrain Induced Rotor Experiment (T-REX) was conducted during March and April 2006, during which time 306 dropsondes were launched from the NCAR G-V aircraft during eleven research flights. T-REX marks the first project where dropsondes were deployed from NCAR's newest aircraft. T-REX is the second phase of a coordinated effort to explore the structure and evolution of atmospheric rotors, which typically occur parallel to, and downstream from, mountain ridge crests. The first phase was a project conducted in 2004 called the Sierra Rotors Project. Both phases included radiosonde launches from the California Central Valley and Owens Valley, however only the second phase included the use of dropsondes.