2.1 ANOTHER LOOK AT THE SIERRA WAVE PROJECT: 50 YEARS LATER Vanda Grubiˇsi´c∗ and John Lewis Desert Research Institute, Reno, Nevada 1. INTRODUCTION aerodynamically-minded Germans found a way to contribute to this field—via the development ofthe In early 20th century, the sport ofmanned bal- glider or sailplane. In the pre-WWI period, glid- loon racing merged with meteorology to explore ers were biplanes whose two wings were held to- the circulation around mid-latitude weather systems gether by struts. But in the early 1920s, Wolfgang (Meisinger 1924; Lewis 1995). The information Klemperer designed and built a cantilever mono- gained was meager, but the consequences grave— plane glider that removed the outside rigging and the death oftwo aeronauts, LeRoy Meisinger and used “...the Junkers principle ofa wing with inter- James Neeley. Their balloon was struck by light- nal bracing” (von Karm´an 1967, p. 98). Theodore ening in a nighttime thunderstorm over central Illi- von Karm´an gives a vivid and lively account of nois in 1924 (Lewis and Moore 1995). After this the technical accomplishments ofthese aerodynam- event, the U.S. Weather Bureau halted studies that icists, many ofthem university students, during the involved manned balloons. The justification for the 1920s and 1930s (von Karm´an 1967). use ofthe freeballoon was its natural tendency Since gliders are non-powered craft, a consider- to move as an air parcel and thereby afford a La- able skill and familiarity with local air currents is grangian view ofthe phenomenon. Just afterthe required to fly them. In his reminiscences, Heinz turn ofmid-20th century, another meteorological ex- Lettau also makes mention ofthe influence that periment, equally dangerous, was accomplished in experiences with these motorless craft, in his case the lee ofthe Sierra Nevada. This Air Force-funded hang gliders, had on his interest in meteorology experiment made extensive use ofthe sailplane, an- (Lettau 1990). Most ofthe flying with the glid- other flying platform whose movement is dictated ers in Germany took place in the Riesengebirge by the air currents. The experiment was called mountains in Sudetes (then eastern Germany, to- the Sierra Wave Project, and it took place in two day southwestern Poland), the Wasserkuppe in the phases, the first in 1951-52 to investigate the well- Rh¨on Mountains (central Germany), and at Rossit- known “Bishop Wave” or “Sierra Wave”, and in ten dunes in the Kurische Nehrung (the 100 km 1955 to study the jet stream as it traversed the tongue ofland in the eastern part ofthe Baltic Sierra Nevada. In this paper, we retrospectively Sea), where sailplanes were launched from the high examine this major mountain meteorology experi- sand dunes (∼70 m above sea level) and flown over ment. Our investigation has multi-faceted purpose: the Baltic. With these aerodynamically designed to uncover the scientific motivation for the experi- gliders, competitions were the vogue in the 1920s ment, to examine the coupling ofsport and science where time/distance records were the primary goals. in this experiment, and the impact ofthe experi- Interest in gliding was sparked in other European ment on the meteorological and soaring communi- countries, notably Sweden, as well as in the United ties. States. Elmira, NY, became the hotbed ofactiv- ity in the US, where the terrain around this city in 2. SAILPLANES upper-New York state was nearly identical to that around Wasserkuppe. As will be seen, some ofthe As part ofthe Treaty ofVersailles, Germany pilots who served in the Sierra Wave Project gained was strictly prohibited from flying motorized craft, their experience at the gliding schools that devel- and was not allowed to engage in the design and oped in the vicinity ofthese sailplane centers. construction ofaircraft. Nevertheless, in this post- WWI period ofintense activity with airplanes, the 3. FLOW OVER MOUNTAINS: EARLY OB- SERVATIONS ∗Corresponding author’s address: Dr. Vanda Grubiˇsi´c, Desert Research Institute, Division of Atmospheric Sci- ences, 2215 Raggio Pkwy, Reno, NV 89512–1095; e-mail: During this period ofinterest in sailplane devel- [email protected] opment, a series ofcontributions related to airflow over mountains appeared in the scientific literature. abutted the Atlas Mountains. He delivered detail Some ofthe observations were made with the aid of maps ofhorizontal pressure perturbations and air- the sailplane, but the earliest studies ofnote were flow modifications induced by this mountain range. simply made with time-lapse photography. Masano From observations associated with these systems, Abe, a physicist trained at the University ofTokyo, he had the basis for his analytical studies. The used a dry photographic plate process to take pic- solutions he obtained—via linearization ofthe ba- tures ofclouds that formedover Mount Fuji (Abe sic equations, assuming sinusoidal variation oforog- 1929). He paid particular attention to the rotary raphy and constant mean wind and stability— motion ofthe clouds (rotation about the vertical exhibited the importance ofinterplay between the axis) as the air traversed the 3.7-km high moun- wavelengths ofthe mountain profile, speed ofthe tain. Sukuei Fujiwara ofthe Central Meteorological current over the mountain, and the stability ofthe Office had theoretically studied this generation of atmosphere. While Queney himselfdid not obser- vorticity in the lee ofFuji and Abe obtained observa- vationally document mountain waves, he predicted tions in support ofthe theory (Fujiwara 1927). Dur- their existence theoretically as one possible solution ing the 1930s, several notable observational studies ofhis analyzed set ofequations. ofairflow over mountains were completed. These Kuttner’s work (Kuettner 1938, 1939) was also were: (1) flow over the Atlas Mountains, mountain comprehensive, with great attention to observa- range parallel to the north African coast (Queney tions ofmountain waves, some ofwhich had been 1936a,b), (2) flow over the Riesengebirge in Sudetes carried out by sailplanes, and conceptual model- (Kuettner 1938, 1939), and (3) flow over the North- ing. The key signature in Kuettner’s work is the ern Pennines, near the border ofEngland/Scotland “Stehende Wolken im Gebirgeslee” (the stationary (Manley 1945)1. We briefly discuss these contri- clouds in the lee ofthe mountain—sometimes called butions with some background information on the the Moazagotl). These clouds were revered by soar- investigators. ing enthusiasts who knew that the appearance of Queney’s study was the most comprehensive with the Moazagotl portended supreme lift for their craft. attention to surface and upper-air observations The associated vertical currents helped the gliders (from pilot balloon) as well as analytical theory. attain heights the order of7 km. They had discov- These papers, Queney (1936a,b), formed his doc- ered that the lift was not associated with thermals toral thesis at the University ofParis. As remem- nor the mechanical lift of air over mountain barriers, bered by his colleague, Pierre de Felice: rather with the stationary cloud downstream ofthe range. In Kuettner’s doctoral thesis (the combined After the competition of Agregation de contribution from the two papers referenced above), Physique (he was first), he went to Taman- he begins by making reference to Wolf Hirth’s alti- rasset (Algeria) at the Geophysical Obser- tude record over Gr¨unau in the lee ofthe Riesen- vatory (seismology, magnetism and meteo- gebirge. His aim is to understand the stationary rology). There he met Jean Dubief...PQ wave that Hirth used to set an altitude record in [Paul Queney] and Dubiefmade several March of1933. Kuettner had been particularly in- measurements in Tamanrasset, specially fluenced by the work ofEnglish classical dynamicists ofwinds aloftwith pilot balloons and 2 Lord Kelvin (William Thomson) and Lord Rayleigh. theodolites. PQ went to the Institute de They had both studied the generation ofstanding Physique du Globe d’Alger, where he regu- waves downstream ofobstacles in rivers and other larly drew meteorological maps and he ob- bodies ofwater. Quoting Kuettner: served the change ofdirection ofthe sur- face wind, south of Mount Atlas when the You know, those English physicists really wind was blowing from the North or North- did outstanding work. I remember read- west.(de Felice 2002, personal communica- ing Lord Kelvin’s work [On the stationary tion) waves in flowing water (Kelvin 1886)]. He motivated the study by recalling the horse- Queney examined a number ofcases ofwhat rep- drawn canal boats where speeds exceeding resented strong synoptic weather systems (includ- the gravity wave speed led to less resistance ing those forcing Mistral) that traversed France on the boat. So clever. (Kuettner 2002, and Spain and passed over the Mediterranean and oral history) 1Manley’s observations were conducted during 1937–1939 but the publication of his results was delayed because of the The flow ofwater past obstacles had appeal to national security reasons during WWII. Kuettner, yet he realized that the Moazagotl was 2 more complicated and would require more in-depth 4. SIERRA WAVE PROJECT investigation. He enlisted the services ofmany sailplane pilots (he was a pilot himself) and they As mentioned in the Introduction, the Sierra made observations ofthe stationary wave in the Wave Project was a major undertaking designed to lee ofthe Riesengebirge in 1937. In accord with study mountain waves and rotors generated in air- Queney’s work, Kuettner emphasized the impor- flow over the southern part ofthe Sierra Nevada, tance ofstability in the air above the mountain. He or High Sierra, in eastern California. This project, also noted the appearance ofa rotary motion at low funded primarily by the U.S. Air Force but also by levels, later referred to as the “rotor”. the Office ofNaval Research 2, involved several orga- Gordon Manley begins his paper (Manley 1945) nizations including the Geophysics Research Direc- by quoting from the Meteorological Glossary (Glos- torate ofthe Air Force Cambridge Research Cen- sary 1930): ter, the University ofCaliforniaLos Angeles, and the Southern California Soaring Association.