THE TERRAIN-INDUCED ROTOR EXPERIMENT A Field Campaign Overview Including Observational Highlights Using the twenty-first-century tools to collect an unprecedented set of observations from the Earth surface to the lower stratosphere, T-REX is poised to resolve a long-standing mystery of atmospheric rotors. A tmospheric rotors are tradition- ally defined as intense low-level horizontal vortices that form along an axis parallel to and downstream of a mountain ridge crest in association with large-amplitude mountain waves. High levels of turbulence characterize rotors, which are known to pose a great hazard to aviation. Recent numerical, theoretical, and observational studies of rotors  Rear view detail of NSF/NCAR HIAPER jet on an air strip in Bishop, CA with the snow-covered White Mountains in the background. (Photo courtesy of Boro Grubišić.) BY V ANDA GRUBIŠIć, JAMES D. DOYLE, JOACHIM KUETTNER, STEPHEN MOBBS, RONALD B. SMITH, C. DAVID WHITEMAN, RICHARD DIRKS, STANLEY CZYZYK, STEPHEN A. COHN, SIMON VOSPER, MARTIN WEISSMANN, SAMUEL HAIMOV, STEPHAN F. J. DE WEKKER, LAURA L. P AN, AND FOTINI KATOPODES CHOW