SIERRA WAVE PROJECT REVISITED 50 Years Later

SIERRA WAVE PROJECT REVISITED 50 Years Later BY VANDA GRUBISIC AND JOHN M. LEWIS Though an important predecessor of modern field experiments, the findings of this 1950s investigation have remained largely out of scientific limelight n the early twentieth century, the sport of manned plished in the lee of the Sierra Nevada. This experi- balloon racing merged with the science of meteo- ment, funded by the Air Force, made extensive use rology to explore the circulation around mid- of the sailplane, another flying platform whose move- latitude weather systems (Meisinger 1924; Lewis ment is in large part dictated by the air currents. The 1995). The information gained was meager, but the experiment was called the Sierra Wave Project, and consequences grave—the death of two aeronauts, its two phases took place in 1951-52 and 1955. The LeRoy Meisinger and James Neeley. Their balloon focus of the experiment was the now well-known was struck by lightning in a nighttime thunderstorm "Sierra Wave" and hazards posed to civilian and mili- over central Illinois in 1924 (Lewis and Moore 1995). tary aviation by such strong mountain-generated dis- After this event, the U.S. Weather Bureau halted turbances. The great achievements in the exploration studies that involved manned balloons. The justifi- of the Sierra Wave in the 1951-52 phase, in which cation for the use of the free balloon was its natural only sailplanes were used, was continued in 1955 with tendency to move as an air parcel and thereby afford the addition of engine-powered aircraft to extend in- a Lagrangian view of the phenomenon. Just after the vestigations to larger distances up- and downstream middle of the twentieth century, another meteoro- and to the interaction of mountain waves with the jet logical experiment, equally dangerous, was accom- stream as it traversed the Sierra Nevada. Appropri- ately, this phase was called the Mountain Wave-Jet Stream Project. In this paper we retrospectively ex- AFFILIATIONS: GRUBiSicf—Desert Research Institute, Reno, amine both components of this major mountain Nevada; LEWIS—National Severe Storms Laboratory, Norman, meteorology experiment that was in many aspects a Oklahoma, and Desert Research Institute, Reno, Nevada CORRESPONDING AUTHOR: Dr. Vanda Grubisic, Division of forerunner of modern mesoscale field experiments. Atmospheric Sciences, Desert Research Institute, Reno, NV 89512 Our investigation has a multifaceted purpose: to place E-mail: [email protected] the scientific motivation for the experiment in its his- DOI: 10.1 175/BAMS-85-8-1 127 torical context, to examine the coupling of the sport In final form 11 February 2004 of soaring and the science of meteorology in this ex- ©2004 American Meteorological Society periment, and to study the impact of the experiment on the meteorological and aviation communities. AMERICAN METEOROLOGICAL SOCIETY AUGUST 2004 BAfft | 1127 Unauthenticated | Downloaded 10/11/21 06:24 AM UTC SAILPLANES. As part of the Treaty of Versailles, FLOW OVER MOUNTAINS: EARLY OBSER- Germany was strictly prohibited from flying motor- VATIONS. During this period of interest in sail- ized craft, and was not allowed to engage in the de- plane development, a series of contributions related sign and construction of aircraft. Nevertheless, in the to airflow over mountains appeared in the scientific post-World War I (WWI) period of intense activity literature. Some of the observations were made with with aviation, the aerodynamically minded Germans the aid of the sailplane, but the earliest studies of note found a way to contribute to this field via the devel- were simply made with time-lapse photography. opment of gliders and sailplanes.1 In the pre-WWI Masano Abe (1929), a physicist trained at the Univer- period gliders were biplanes whose two wings were sity of Tokyo, used a dry photographic plate process held together by struts. But in the early 1920s, to take pictures of clouds that formed over Mount Fuji Wolfgang Klemperer designed and built a cantilever called the "Turusi." He paid particular attention to the monoplane glider that removed the outside rigging rotary motion of the clouds (rotation about the verti- and used .. the Junkers principle of a wing with in- cal axis) as the air passed the 3.7-km-high mountain. ternal bracing" (von Karman and Edson 1967, p. 98). Sukuei Fujiwara (1927) of the Central Meteorologi- Theodore von Karman and L. Edson (1967) give a cal Office had theoretically studied this generation of vivid and lively account of the technical accomplish- vorticity in the lee of Mount Fuji and Abe obtained ments of these aerodynamicists, many of them uni- observations in support of the theory. versity students, during the 1920s and 1930s. During the 1930s, several notable observational Because gliders are nonpowered craft, considerable studies of airflow over mountains were completed. skill and familiarity with local air currents is required These studies focused on 1) flow over the Atlas Moun- to fly them. In his reminiscences, Heinz Lettau makes tains, a range parallel to the north African coast mention of his experiences with motorless craft, in his (Queney 1936a,b), 2) flow over the Riesengebirge in case hang gliders, and the influence they had on his Sudeten (Kuttner 1938, 1939), and 3) flow over the interest in meteorology (Lettau 1990). In Germany, Northern Pennines, near the border of England- most of the flying with sailplanes took place in the Scotland (Manley 1945).2 We briefly discuss these Riesengebirge mountains in Sudeten (then eastern contributions with some background information on Germany, today southwestern Poland bordering the the investigators. Czech Republic) and the Wasserkuppe in the Rhon Paul Queney's study delivered detailed analyses of Mountains (central Germany). Gliders and, to a lesser surface and upper-air observations (from pilot bal- extent, sailplanes were also flown over the Rossitten loons) in concert with analytical theory. Two papers dunes in the Kurische Nehrung (the 100-km tongue (Queney 1936a,b) formed his doctoral thesis at the of land in the eastern part of the Baltic Sea), where University of Paris. As remembered by his colleague, the planes were launched from the high sand dunes P. de Felice (2002, personal communication),3 (-70 m above sea level) and flown over the Baltic. With these aerodynamically designed sailplanes, com- After the competition of Agregation de Physique (he petitions were the vogue in the 1920s where time/ was first), he went to Tamanrasset (Algeria) at the distance records were the primary goals. Interest in Geophysical Observatory (seismology, magnetism gliding was sparked in other European countries, no- and meteorology). There he met Jean Dubief... PQ tably Sweden, as well as in the United States. Elmira, [Paul Queney] and Dubief made several measure- New York, became the hotbed of activity in the United ments in Tamanrasset, specially of winds aloft with States where the terrain around this city in upper New pilot balloons and two theodolites. PQ went to the York State was nearly identical to that around Institute de Physique du Globe d'Alger, where he Wasserkuppe. As will be seen, some of the pilots who regularly drew meteorological maps and he observed served in the Sierra Wave Project gained their expe- the change of direction of the surface wind, south rience at the schools that developed in the vicinity of of Mount Atlas when the wind was blowing from the these sailplane centers. North or Northwest. 1 A sailplane is a glider of special design that allows it to rise in an upward air current. The terms are often used synonymously. 2 Manley's observations were conducted during 1937-39 but the publication of his results was delayed because of the national se- curity reasons during WWII. 3 Bracketed information within quotes was provided by the authors. 1128 I BAF15- AUGUST 2004 Unauthenticated | Downloaded 10/11/21 06:24 AM UTC Queney examined a number of cases in connection ity wave speed led to less resistance on the boat and with strong synoptic weather systems (including those to more income for the owner. So clever. forcing the Mistral) that traversed France and Spain and passed over the Mediterranean and abutted the The flow of water past obstacles had appealed to Atlas Mountains. He constructed detailed maps of Kuettner, yet he realized that the Moazagotl was more horizontal pressure perturbations and airflow modi- complicated and would require more in-depth inves- fications induced by this mountain range. From ob- tigation. Together with Hirth, he enlisted the services servations associated with these systems, he had the of many sailplane pilots (he was a pilot himself) and basis for his analytical studies. The solutions he ob- they made observations of the stationary wave in the tained—via linearization of the basic equations, as- lee of the Riesengebirge in 1937 with a fleet of 25 in- suming sinusoidal variation of orography and con- strumented gliders participating in a local gliding stant mean wind and stability—exhibited the contest. Using 22 flight reports, covering over 65 flight importance of interplay between the wavelengths of the hours spent in the wave system on 21 May 1937, they mountain profile, speed of the current over the moun- were able to determine the detailed three-dimensional tain, and the stability of the atmosphere. While Queney structure of the complete lee-wave system (Kiittner himself did not observationally document mountain 1938). In accord with Queney's work, Kuettner em- waves, he predicted their existence theoretically as phasized the importance of stability in the air above one possible solution of his analyzed set of equations. the mountain for the formation of these waves. He Kuettner's (1938, 1939) work paid great attention also noted the appearance of a rotary motion at low to observations of mountain waves carried out by sail- levels, which he referred to as the "rotor." planes, and to conceptual modeling.

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