The Sierra Wave Project was a U.S.-Air-Force-funded field study of mountain waves involving a two-phase field experiment. The first phase of the field experiment took place in the winter of 1951--52, the second phase in the spring of 1955. The site of both phases of the field work was Owens Valley in the lee of the Sierra Nevada. The Project involved a number of cooperating agencies including the Southern California Soaring Society, Air Force Cambridge Research Center, and the Meteorology Department at the University of California at Los Angeles (UCLA).

The principal research tool during the Sierra Wave Project was an instrumented sailplane tracked in flight from ground by a network of photo-theodolites. Other data sources of the Sierra Wave Project include cloud photography, surface measurements from recording instruments and mobile platforms, pilot balloon and radiosonde soundings, and regular Weather Bureau synoptic data. In conjunction with sailplanes, in the second phase, use was also made of the instrumented powered aircraft (B-29 and B-47). In this talk we will: 1) discuss the most important contributions of the Sierra Wave Project to our knowledge of mountain waves and rotors, and 2) compare and contrast observational strategies and available instrumentation then and now.