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.

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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.

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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. The key signa- Gordon Manley (1945) begins his paper: ture in his work was the "Stehende Wolken im Gebirgslee" (the stationary clouds in the lee of the The Helm wind is a violently cold easterly wind mountain, locally called the Moazagotl). These clouds blowing down the western slope of the Crossfell were revered by soaring enthusiasts who knew that Range [N. Pennines, maximum altitude ~ 1 km] .. . the appearance of the Moazagotl portended supreme when the helm is blowing, a heavy bank of cloud, lift for their craft. The associated vertical currents the Helm Cloud, rests along the Crossfell Range, helped the sailplanes attain heights on the order of and at a distance of three to four miles from the foot 7 km. They had discovered that the lift was neither of the Fell, a slender, nearly stationary roll of whirl- associated with thermals nor the mechanical lift of air ing cloud, the Helm Bar, appears in mid-air and over mountain barriers, but rather with the station- parallel to the Helm Cloud. The cold wind blows ary cloud downstream of the range. In Kuettner's strongly down the steep fell sides until it nearly doctoral thesis (the combined contribution from the comes under the Bar where it suddenly ceases . . . two papers referenced above), he began by making The space between the Helm Cloud and Bar is usu- reference to Wolf Hirth's seminal flight in mountain ally quite clear although the rest of the sky may be waves over Grunau in the lee of the Riesengebirge. His cloudy. aim was to understand the stationary wave that Hirth encountered in March of 1933 that took him to more Over a period of a few years (1937-39), Manley pains- than 1400 m above a hill of only 200 m in height. Hirth takingly collected data from the ground on the helm correctly interpreted this updraft as a part of a wave wind and attendant meteorological features in order motion caused, not by this small hill, but by the much to develop a detailed description of the helm wind higher Riesengebirge further upstream. Kuettner had phenomenon. He suspected (with the aid of a limited been particularly influenced by the work of English number of upper-air observations) that the helm classical dynamicists Lord Kelvin (William Thomson) cloud was associated with a strong inversion and and Lord Rayleigh. They had both studied the gen- stable layer immediately above it. He also noted that eration of standing waves downstream of obstacles in on some occasions, not only one, but as many as four rivers and other bodies of water. Quoting Kuettner or five standing waves were present downwind of the (2002, personal communication), mountains—equally spaced at distances of about 4 miles. The helm bar, a roll cloud, was also observed I remember reading Lord Kelvin's work [On the sta- as a regular feature positioned not too far from the tionary waves in flowing water (Kelvin 1886)]. He foot of the range. was motivated to do the study by recalling the horse- The vicissitudes of World War II (WWII) brought drawn canal boats where speeds exceeding the grav- intensive field investigations of mountain waves to

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC almost a standstill. During the 1940s, only a few The initial thrust for the Sierra Wave Project came smaller field investigations took place, most notable from the Southern California Soaring Association among them the field studies by Krug-Pielsticker (SCSA). By the late 1940s, the SCSA had grown (1942) in the eastern Alps, and Forchgott (1949) in significantly in membership to some 250 members, the mountains of, then, Czechoslovakia. The 1950s with a number of them with strong engineering announced a new era in the mountain wave field in- and scientific backgrounds, including, for example, vestigations that started with the Sierra Wave Project Wolfgang Klemperer and Paul MacCready. The first in the United States. SCSA proposal for study of the Sierra Wave, on which Klemperer took a leadership role, was sent to THE SIERRA WAVE PROJECT. The Sierra the Office of Naval Research (ONR). Both the U.S. Wave Project was the first post-WWII mountain me- Air Force and the Navy had suffered significant loss teorology field experiment designed to study moun- of life and planes in aviation accidents over the high tain lee-wave phenomena. The focal area of both field terrain of Asia and Europe during both WWII and phases was the Owens Valley in the lee of the south- the Korean War. In part, the proposal was aimed at ern Sierra Nevada, or High Sierra, in eastern Califor- gaining a more complete understanding of airflow nia. The Owens Valley, a narrow rift valley confined over high mountain ranges in an effort to curtail such between two high mountain ranges, is the location of accidents. Although the Navy had interest in the the steepest orographic gradients in the contiguous project, the lack of a theoretical component led to a United States. The two mountain ranges are the Sierra rejection of the proposal. Undeterred, and taking Nevada to the west and the White-Inyo Range to the advantage of the reviews, Klemperer and Victor east. The average elevation difference of 3000 m be- Saudek, an SCSA member and an engineer, ap- tween the valley floor and the Sierra crest, with a num- proached the University of California, Los Angeles ber of peaks above 4000 m, including the highest peak (UCLA), Meteorology Department and obtained in the contiguous United States (Mount Whitney, their commitment to contribute to a revised pro- 4418 m), occurs over a horizontal distance of less than posal. This revised proposal was sent to the U.S. Air 10 km (Fig. 1). Force through its Geophysical Research Directorate (GRD) and affiliated Air Force Cambridge Research Center (AFCRC). This second proposal was well re- ceived and a decision was made to fund the project. As it evolved from an initial proposal to an ambitious and well-organized exploration of mountain waves, rotors, and turbulence, the Sierra Wave Project involved several organiza- tions, including the SCSA, AFCRC, UCLA, the U.S. Navy and the U.S. Weather Bureau.

Project team. The project had both an observational and a theoretical program. The former was spearheaded by the SCSA and its FIG. I. Landform map of southern California. The yellow rectangle is centered pilots who had accumu- on Owens Valley, a narrow rift valley in between the Sierra Nevada to the lated considerable experi- west and the White-Inyo Range to the east. The Owens Valley was the site of ence in flying the Sierra the Sierra Wave Project. Wave during the late 1940s

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC and early 1950s during several Bishop wave camps. Among those attempting to use the mysterious Sierra Wave to achieve new altitude and distance records at that time was P. MacCready, then a graduate student at the California Institute of Technology and an excellent sailplane pilot. In this context it is appropriate to mention the project visionaries, Robert Symons and Victor Saudek, enthusiastic members of the SCSA and the driving force behind the project. We refer the reader to the historical review of these men and their work in an interesting and informative exposition on soaring the "Bishop Wave" (later called the "Sierra Wave" and dubbed "the Monster" in the books title) (Whelan 2000). Symons, a local Bishop man, was particularly familiar with the powerful mountain waves. Quoting from Whelan (2000, p. 30):

FIG. 2. The Sierra Wave Project pilots and key people Symons can perhaps be best summarized as "versa- on the field location in Owens Valley on 3 Feb 1952. Back tile, energetic, and visionary." He was simulta- row, from left to right: Joachim Kuettner, Wolfgang neously inspirational and remarkably creative and Klemperer, Larry Edgar, and John Robinson. Front row, productive ... he served to identify Bishop as the from left to right: Vic Saudek, Dick Eldridge, and Ray logical site for the scientific study which would for Parker. (From Harold Klieforth's private collection.) the first time quantify the mysterious, and poten- tially deadly, mountain wave. meteorological observer, Klieforth, together with Kuettner, carried out an important job on the ground It was Saudek, with his wealth of experience in the as well, making weather forecasts that were impor- aviation industry, who brought managerial, engineer- tant for reaching decisions on flight operations. ing, and operational skills to the project (Whelan Figure 2 shows some of key members of the obser- 2000, p. 61), becoming its technical supervisor. vational team on site in Owens Valley. Klemperer was a noted aviation engineer and a soar- The center of theoretical activities was the Depart- ing pilot. Among others, he designed the instrument ment of Meteorology at UCLA where Jorgen panel in the Pratt-Reed sailplanes, which with their Holmboe and Jacob Bjerknes were the leaders. The side-by-side seats allowed for a copilot. The pilots— theoretical program was headed by Holmboe, a John Robinson, Lawrence Edgar, and Raymond Norwegian meteorologist who had joined Bjerknes in Parker—were champion soaring pilots with world the 1940s in establishing a meteorology program at altitude records to their names. Robinson also was UCLA. Holmboe was the theoretically minded aca- 5 times the American soaring champion. They had demician, and Bjerknes, with his physical insight and all served in the U.S. Army Air Force during WWII synoptic prowess, added an important complement as sailplane pilot instructors at Twenty Nine Palms, to the study (H. Klieforth 2003, personal communi- California. One of the key roles in the observational cation). The two men complemented each other in program was played by Joachim Kuettner from personality as well as in their approach to meteorol- AFCRC. Having emigrated from Germany following ogy. As remembered by Sheldon Levin (1997) one of WWII, Kuettner was a contract monitor at GRD who the students in UCLA's Air Force training program got actively involved in the newly funded project as during WWII, a project scientist. As an accomplished sailplane pilot himself, and with his Ph.D. work in Germany on Jacob Bjerknes was tall, raw-boned, with a shock of documenting mountain waves in the lee of the brown hair. He moved slowly and deliberately and Riesengebirge, Kuettner was an invaluable asset to the spoke the same way . . . Bjerknes' companion was project. An SCSA pilot Betsy Woodward and a Jorgen Holmboe—slender, intense, and a chain UCLA graduate student Harold Klieforth often smoker. Holmboe had a heavy Norwegian accent, served as onboard scientific observers, copilots, and which was not easy to understand. He obviously photographers, recording meteorological informa- thought in Norwegian. Then he had to translate to tion during the flights. In addition to his role as the English.

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC In addition to Holmboe and Bjerknes, several of platform was a sailplane. The research "fleet" Holmboe's graduate students, including Morton consisted of 2 two-seater Pratt-Read sailplanes, Wurtele and Joseph Knox, were permanent members equipped with a clock, an altimeter, indicators for the of the theoretical group at UCLA. The group was rate of climb, airspeed, and direction (compass), an regularly enlarged by long-term visitors, most nota- accelerometer, an outside (fuselage) thermometer, bly P. Queney and Einvar Hoiland, who stayed 1-2 yr and a barograph (Fig. 4). In order to produce a con- at a time (Fig. 3). In addition, a number of short-term tinuous record of the flight data, the instrument panel visitors frequented UCLA, including Phil Thompson was photographed at 1- or 2-s intervals on 16-mm from the AFRC, and Enok Palm, Arnt Eliassen, Arne film by two cameras in the rear of the cockpit. The Foldvik, and Ragnar Fjortoft from the University of number of measured physical parameters and the Oslo, Norway, who had visited UCLA on several oc- recording system were quite modest compared to ca- casions, thus, giving a strong international feel to the pabilities of modern research aircraft whose data- group at UCLA. In that respect, the Sierra Wave recording systems are capable of recording high- Project is similar to several other post-WWII meteo- frequency data (up to 10 Hz) for dozens of variables rological projects in the United States that have at- simultaneously and even displaying them during the tracted a large number of European scientists (Harper flight. Yet this system afforded the Sierra Wave 2004). Project researchers a continuous record of sailplane These and other members of the project team flights for the postanalysis. The total flight time of along with their affiliation and responsibilities are sailplanes was limited to 4.5 h by the oxygen supply, identified in Table 1. A strong enthusiasm for discov- and the tracking operation was limited by the film ery was shared by members of both the observational length to 1.5 h. and theoretical camps. The excitement about work- The tracking of sailplanes from the ground was ing together on unraveling the mysteries of the atmo- carried out by a network of Mitchell phototheodolites sphere was as much palpable among the pilots in the provided by the U.S. Navy and operated by the U.S. field as it was among the theoreticians at UCLA pon- Air Force. A ground-based radar unit was used as the dering over equations and their mathematical descrip- ground radio center for coordination of activities. tions of the phenomena. Operation of the Raydist (all-weather radio location) system, also provided by the U.S. Navy, was entirely Observational techniques and instrumentation. In the experimental. These instruments were manually op- 1951-52 field project the main observational erated in tracking the sailplanes but the readings of the phototheodolites and the radars were photographed simultaneously and automatically at 5-s intervals on 35-mm film. The Raydist tracking system produced electronic sig- nals that were recorded directly. Compared to the automatic inertial navigation system (INS) and GPS tracking systems onboard modern research aircraft, the methods for de- termining the position of sailplanes used by the Sierra Wave Project researchers were painstakingly com- plex. Due to the limitations of both the ground-tracking and the data- recording system onboard sailplanes, useful data were obtained in only 50% of the research flights conducted in the 1951-52 season (11 research flights FIG. 3. The Sierra Wave Project scientists on the field location in Owens Valley during a visit on 3 Feb 1952. From left to right: Paul on 9 different days). Queney (University of Paris), Jacob Bjerknes (UCLA), Joachim The corrected quantities derived Kuettner (USAF Cambridge Research Center), and Jorgen Holmboe from the airborne measurements (UCLA). (From Harold Klieforth's private collection.) alone and their estimated accuracies

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC were (i) time (± 0.5 s), (ii) TABLE 1. Sierra Wave Project team members. pressure altitude (± 12 m at MSL to ± 30 m at 12,000 m), Team member Position/Responsibility (iii) true air speed (± 1 m s_1), (iv) heading (± 3°), (v) sink- Southern California Soaring Association ing speed (±0.1 m s-1), and Robert Symons Project visionary/Pioneer pilot

temperature (± 1.5°C). The Victor Saudek Project visionary/Aeronautical engineer synthesis of tracking and airborne data, in which assump- Wolfgang Klemperer Project initiator/Aeronautical engineer tions of steady state and two- Raymond Parker Primary soaring pilot dimensionality in a coordi- nate plane perpendicular to Lawrence Edgar Primary soaring pilot the Sierra crest were intro- John Robinson Primary soaring pilot duced, produced the follow- Betsy Woodward Copilot/Onboard observer and photographer ing physical quantities at estimated accuracies: the hori- Karl-Eric Ovgard Visiting pilot (Sweden) zontal component of the Air Force Cambridge Research Center wind perpendicular to the Sierra crest (± 5%), vertical Philip Thompson Director, Meteorological Research Laboratory wind speed (± 5%), potential Joachim Kuettner Project scientist/Field director/Pilot temperature (± 2 K), and D value (i.e., altimeter correc- University of California, Los Angeles tion) (from ± 30 to ± 60 m). Jorgen Holmboe Department chair/Project leader

Other sources of data in- Jacob Bjerknes Faculty/Advisor cluded the following: Paul Queney Visiting faculty (France)

a) radiosonde ascents from Einvar Hoiland Visiting faculty (Norway)

Lodgepole, Sequoia Na- Harold Klieforth Graduate student/Onboard meteorologist tional Park, and Merced, Castle Air Force Base, Morton Wurtele Graduate student upwind of the Sierra Joseph Knox Graduate student crest; b) still photographs and Einar Hovind Graduate student time-lapse films, from air James Edinger Graduate student and from the ground, of David Johnson Graduate student the Sierra wave clouds; c) surface measurements Leon Sherman Graduate student from recording instru- Rolando Garcia Graduate student ments (barographs, ther- mographs, and anemo- U.S. Air Force graphs) from a number William Ross Officer of points across the McKissick Officer Owens Valley, the eastern Sierra, and the west- 10 enlisted men Operation of Theodolites ern Inyo slopes; U.S. Navy d) surface measurements from a mobile platform Cdr. Wilson Liaison (a car with an altimeter, Lester Elliott Instrument specialist aneroid barometer, thermometer, anemom- U. S. Weather Bureau (Bishop, CA) eter, and photo cam- Charles Patterson (MIC) and staff Supplied weather data 1951-52 eras) across the Owens Valley; Elvyn Pye (MIC) and staff Supplied weather data 1955

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC the ground tracking was not supported in this phase of the experiment. The powered aircraft were equipped with the most advanced instrumentation of the day, particularly the wind-measuring system based on a new application of a down-looking Doppler radar, providing true velocity, heading, and the vertical displacement from the ground. In the three coordinated research missions that were carried out during this field campaign (on 1, 10, and 13 April 1955), the two powered aircraft carried out simultaneous east- west cross-mountain transects at FIG. 4. One of two Pratt-Read sailplanes of the Sierra Wave Project at a 6-9 km (20-30 kft, B-29) and 9- runway in Bishop, CA. (From Harold Klieforth's private collection.) 12 km (30-40 kft, B-47) from far upwind to far downwind of the e) meteograph flights made by the BT-13 aircraft Sierra Nevada. At the same time, the sailplanes were used for sailplane towing; documenting the lower portions of the wave over the f) double-theodolite pilot-balloon ascents made by Owens Valley before reaching its upper parts by stay- the Weather Bureau at the Bishop International ing in the strongest updrafts. The sailplanes were per- Airport Authority in Owens Valley; and fectly suited for measurement of vertical velocities be- g) synoptic data and weather logs, including surface cause, due to a much smaller wing loading, they were cloud observations. capable of responding to wind gusts within seconds or within horizontal distances on the order of 50 m. The hallmark of the 1955 Mountain Wave-Jet For powered aircraft, depending on the wing load- Stream experimental campaign was the addition of ing, that distance was closer to 500 m. With powered powered aircraft to enable the study of mountain aircraft flying along horizontal cross-mountain waves and jet stream interaction. The addition of air- traverses at a constant level, exploiting the constant craft was also important to obtain mesoscale informa- altitude/constant power (thrust) settings of their au- tion needed by theoreticians, which was not possible topilots, it was possible to construct vertical cross sec- with sailplanes only. The Air Force's propeller-driven tions showing wave amplitudes as well as wind speed B-29 and jet B-47 bombers and their crews joined the and temperature variations at several levels and to sailplane teams in a few coordinated flight missions uncover the vertical structure of mountain waves in in the spring of 1955. By 1955, only one of the two the upper troposphere and lower stratosphere. Pratt-Read sailplanes from the 1951-52 field phase It should be noted that special attention and ar- was still in a flying condition. In addition to the sur- rangements were made in both field phases for ob- viving Pratt-Read sailplane, the second sailplane in taining accurate 48-h weather forecasts in support of the 1955 project was a tandem-seat Schweizer 2-25, the field operations. During the field projects, the syn- an overall better-performing sailplane than the Pratt- optic weather analyses and forecasts were provided by Read, but with insufficient interior space that could the U.S. Weather Bureau facsimile charts. In order for not carry both a full instrumentation load and an ob- these products to reach the operations center at the server. Additionally, a much denser network of radio- Bishop Airport in time for making flight decisions, sonde ascents in the vicinity of the Sierra Nevada, with there was a dedicated land line put in place between the three soundings per day, was available in the 1955 Weather Bureau offices in Los Angeles and the Bishop phase due to a close monitoring of atmospheric con- Airport to ensure a timely transfer of facsimile maps. ditions during nuclear tests at the Nevada test site in nearby southern Nevada. Major observational findings. According to Holmboe The instrumentation on the sailplanes in the 1955 and Klieforth (1957), mountain waves observed over campaign was similar to that in 1951-52. However, the Owens Valley were classified into three categories:

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC 1) strong waves with wavelengths of 13-32 km, craft in the Mountain Wave-Jet Stream field phase 1200-2400-m maximum altitude variation of a was also valuable for obtaining a more accurate record streamline, and vertical wind speed of ±9 to of roll cloud turbulence, which can be quite intense ±18 m s_1 (Fig. 5) [As stated in Holmboe and in a strong wave such as that of 1 April 1955, where Klieforth (1957) "the near-legendary reputation vertical gust velocities exceeding 9 m s_1 were re- of the Sierra Wave derives from the spectacular corded 13 times within 50 s (Fig. 8). phenomena associated with the lee waves of strong Among the major contributions of the Sierra Wave intensity."], Project was also a well-documented synoptic clima- 2) moderate waves with wavelengths of 8-13 km, tology of the lee-wave occurrences downwind of the 600-1200-m maximum altitude variation of a Sierra Nevada, and the effect of this mountain range streamline, and vertical wind speed of ±4.5 to on Pacific storms. The latter included the mesoscale ±9 m and pressure and airflow anomalies, cloud forms, and the 3) weak waves with wavelengths of 4-8 km, 150- associated precipitation patterns (appendix in 600-m maximum altitude variation of a stream- Holmboe and Klieforth 1954; chapter 5 in Holmboe line, and vertical wind speed of ±1.5 to ±4.5 m s-1, and Klieforth 1957). Two principal cases studies, those marginally strong to support a sailplane. relating to the strong mountain lee waves of 18 December 1951 and 1 April 1955, provide the most Rotors and zones of low-level turbulence were fre- detailed analyses to date of the concurrent evolution quently found beneath strong mountain lee waves and interaction of synoptic-scale, mesoscale, and even (Fig. 5). Two basic types of roll clouds, on top of ro- smaller-scale phenomena, and their effect on local tors, were identified by the Sierra Wave investigators: weather events in the proximity of the Sierra Nevada. (i) a "normal" type roll cloud, preferably located under the crest of lee waves, paralleling the topographic Major theoretical accomplishments. From the earliest divide and following its bends, and (ii) a severe roll contribution to the theory of mountain waves by cloud appearing to reach levels as high as 9 km and Queney (1936a,b) and the first complete solution for forming a straight, almost vertical wall a considerable distance downstream from the base of the lee slope (Fig. 6). In the latter case there is no apparent trail- ing edge to the roll cloud, which extends eastward over the White and Inyo Mountains, and the flow is similar in appearance to a hydraulic jump (Kuettner 1959). Among the accomplishments of the 1955 field season was the documentation of the vertical structure of mountain waves in the stratosphere and of spatial variations of temperature and horizontal velocities at constant levels from the windward to the leeward side of the mountains pass- ing through a strong moun- FIG. 5. Streamlines in a strong mountain wave and "normal" rotor on 16 Feb tain wave such as that of 1952. Dashed lines (without arrows) show the sailplane trajectory projected 1 April 1955 (Fig. 7). The onto a west-to-east vertical cross section perpendicular to the axis of the addition of powered air- Owens Valley near Independence. (From Holmboe and Klieforth 1957.)

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC became interested in mountain meteorology. Richard Scorer read Queney's (1947, 1948) papers and saw that he could make an extension to that work. Quoting Scorer (1987, p. 3):

He [Queney] had a uniform windspeed for the profile and it seemed to me that that was taking a very special case, so I introduced the variabil- ity of the windspeed which turned out to be just as important as the variation in temperature. But Queney had the method, and ... I just applied this method and had to make a model which was fairly FIG. 6. Typical locations within the Owens Valley of roll clouds associated with realistic. It wasn't very normal (AA) and severe (BB) rotors (from Kuettner I 959). difficult because I had all the knowledge of small-amplitude waves over special mountain shapes what the atmosphere did from my forecasting work derived by a German mathematician Gerhardt Lyra and that produced a paper which has, in fact, been the (1940, 1943), the theoretical treatment of mountain one most referred to that I ever wrote [Scorer 1949]. waves had been considerably advanced in the late 1940s by Queney (1947, 1948), who had carried out None of these early developments took place at this work during his long-term visit at the University UCLA, however. As remembered by M. Wurtele of Chicago. Similar to the early observational studies, (2002, personal communication), then a mathemati- in all likelihood, these two earliest mathematical de- cally well-trained Ph.D. student of meteorology at velopments were entirely independent. While work- UCLA, ing on an applied mathematical problem motivated by Kuettner's observational work on lee waves, Lyra There was no work on mountain waves at UCLA ostensibly was unaware of Queney's work and vice prior to the Sierra Wave Project. That was the be- versa. With wartime Germany getting progressively ginning. We started from ground zero ... I saw it more isolated, the situation that had continued dur- [the Sierra Wave Project] as an opportunity. The ing the post-WWII period, it is easy to understand idea intrigued me and still does ... I saw him that these two theoreticians were unaware of each [Queney] as a mentor. other's work. Both of them had derived the steady- state analytical solutions for small-amplitude waves The Sierra Wave Project had provided a new im- launched by airflow over two-dimensional orography petus for the theoretical work on mountain waves. under assumption of the constant wind and stability The two most important theoretical problems that profiles adopting, however, different mountain pro- had occupied scientists at that time were the indeter- files. Before the beginning of the Sierra Wave Project, minateness of the steady-state solutions of the Lyra- further extension of their theoretical model and its so- Queney model, and the need to incorporate more re- lutions for a two-layer atmosphere with constant but alistic wind profiles in their models in order to explain differing values of wind speed and stability in each layer structures of the actually observed lee waves in the at- was developed by R. Scorer (1949), a student of G. I. mosphere. The lack of uniqueness of the steady-state Taylor at Cambridge University in the late 1940s, who solutions in the Lyra-Queney model was inherited

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC FIG. 7. (top) Clouds at five different levels in a strong mountain wave on I Apr 1955 with the roll cloud at approximately 4.5 km, and the highest wave cloud close to 12 km. In the original photo, the view is southward over Owens Valley from 9 km with the Sierra Nevada to the right. Shown is an inverted im- age of the original photo in which the Sierra Nevada is now to the left, (bottom) A compos- ite display of the B-29 and B-47 measurements of temperature and derived streamline displace- ments over the Sierra Nevada in a strong mountain wave on I Apr 1955 (from Holmboe and Klieforth 1957).

from the classical investigations of Lords Rayleigh fied model, were, however, unsatisfactory from the (1883) and Kelvin (1886) for waves on the surface of formal mathematical point of view. They were also, homogenous and incompressible current of finite particularly Rayleigh's approach, suggestive of a depth flowing over a stationary corrugation at the bot- wrong physical process through which the steady state tom. In order to assure the uniqueness of their steady- was achieved. state solutions and obtain waves downwind of the ob- At UCLA, the most significant contributions to stacle, Rayleigh added a small frictional term to the the solution of both of these problems in the Lyra- equations, whereas Kelvin imposed a so-called mo- Queney model were made by M. Wurtele, who was notony condition requiring that the effect of the ob- inspired by remarkable examples of application of stacle must be negligible at a moderate distance up- classical mathematics to physical problems in Lyra's stream. These physically based approaches, adopted and Queney's work and fueled by many stimulating also by Lyra and Queney in the continuously strati- interactions with Queney during his first stay at

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC FIG. 8. Vertical gust velocities as obtained by the flight analyzer onboard B-29 on I Apr 1955.

UCLA in the early 1950s. For the indeterminateness After obtaining his Ph.D. at UCLA, Wurtele built of the steady-state solutions, Wurtele solved an ini- a successful scientific career, remaining interested in tial value problem (Wurtele 1953b) extending an ear- problems of gravity and gravity-inertia waves lier work and approach developed by Hoiland for the (Wurtele et al. 1996), with the Sierra Wave Project Kelvin-Reyleigh model (Hoiland 1951, Wurtele leaving an indelible mark on him: 1953a). Analyzing the asymptotic behavior of the initial value problem solutions at large times, Hoiland I admire that field program very much. The whole and Wurtele showed that their solutions approach question of gravity or gravity-inertia waves, the the known steady-state solutions, thus, removing all theory of which may be applied to lee waves, is a big formal objections associated with the steady-state so- industry now. I don't know whether it would have lutions. The physical process through which the developed that way without the Sierra Wave Project steady state was achieved is that of wave dispersion, or not (M. Wurtele 2002, personal communication). where all harmonics but the one whose phase speed matches the speed of the current propagate away While there was not much interaction between the from the mountain, with the stationary small- theoretical and observational programs of the Sierra amplitude wave setting up on the downwind side of Wave Project, occasional visits of the UCLA theore- the mountain. Wurtele had also developed linear so- ticians to the field location in Owens Valley did oc- lutions for two-dimensional, one- and two-layer at- cur. During one such visit in early 1952 (Fig. 3), the mospheric models with continuous stratification and review of data and photographs obtained during the vertical wind shear (Wurtele 1953c). While the se- 18 December 1951 strong lee-wave case led}. Bjerknes lected linear wind profiles were mathematical ab- to suggest a hydraulic jump analogy for the observed stractions, they provided a fairly good approximation flow, and to recommend mobile ground observations to the wind speed profiles observed during the Sierra across Owens Valley under the roll cloud. His recom- Wave Project. Consequently, the two-layer model, mendations were adopted and mobile observations with the Couette flow (constant shear, constant sta- were carried out during the spring of 1952 by J. Knox bility) in the troposphere and the uniform wind in (1954). Additional theoretical work on the applica- the stratosphere, was particularly successful in repro- tion of hydraulic theory to the development of rotors ducing the observed wavelengths for a number of in the lee of the Sierra Nevada was later carried out strong lee-wave cases from the Sierra Wave Project. by J. Kuettner at the Cambridge Air Force Research This model was further extended by Holland's stu- Center after the conclusion of both field phases dent Palm (1955) to include multiple layers. These (Kuettner 1959). theoretical models could not, however, reproduce the In the context of hydraulic flow analogies for the large amplitude of the Sierra Wave because, being lin- Sierra Wave, it is appropriate to mention Robert Long ear models, they could only describe small-amplitude and his outstanding theoretical and laboratory work perturbations from the assumed mean atmospheric at the Johns Hopkins University. While not formally state. affiliated with the Sierra Wave Project, Long had a

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC keen interest in the project's findings (Long 1953a), Wave Project was believed to be a consequence of which in part motivated his subsequent work on large accelerations in airflow over mountains was large-amplitude mountain waves and his theoretical shown to be primarily a human error, with pilots fail- hydrodynamic studies (Long 1953b, 1954, 1955). ing to carefully observe altimeter changes while flying through strong downdrafts and experiencing se- Contributions to aviation safety. One of the major ac- vere turbulence. complishments of the Sierra Wave Project was the A condensed version of the Holmboe and Klieforth first comprehensive formulation and documentation (1957) report was later put together by the Air Force, of aviation safety hazards associated with flying in and used in training of the Air Force and Navy pilots mountainous terrain. Given the importance of these concerning the likelihood of mountain wave-induced findings for military, commercial, and private avia- turbulence under different synoptic situations. In tion, 42,000 copies of the report summarizing the haz- spite of the wide distribution of the Sierra Wave ards of flying in mountain waves (Kuettner and Project findings in the aviation communities, aircraft Jenkins 1953) were distributed in 1953 to U.S. mili- accidents in mountainous terrain continued to occur. tary and commercial airline pilots, long before all of Both Wurtele and Klieforth frequently served as ex- the data from the project had been reduced and sub- pert witnesses or consultants in court cases or inves- jected to scientific analysis. In addition, this and other tigations of such accidents (Wurtele 1970). reports from the Sierra Wave and Mountain Wave- Jet Stream Projects were disseminated widely within SUMMARY. The confluence of interest in moun- the soaring communities in the United States and tain waves by the soaring community and research abroad. The latter is not surprising given the pivotal meteorologists was the stimulus for the Sierra Wave role the California Soaring Association pilots played Project. With little doubt, the primary impetus came in these experiments. from the Southern California Soaring Association The combined phenomena of mountain waves and and the contingent of its pilots who have accumulated rotor flows were found to present serious hazards to experience flying in the Sierra Wave. Funding for re- aviation. In the order of severity, these hazards are (i) search, however, demanded that a theoretical com- downdrafts, (ii) turbulence, (iii) spatial and tempo- ponent be added and, thus, the UCLA team headed ral changes of upper-level wind speed and direction, by J. Holmboe entered the project. The interest of the (iv) in-flight icing in the roll- and lenticular clouds, Air Force in the proposed exploration of mountain and (v) strong winds and wind shear near mountain lee waves and the associated aviation safety hazards crest level. was high, due to wartime loses of aircraft in moun- The most significant areas of downdraft were tainous terrain that needed to be understood and found on the lee slope of the mountain range and at similar accidents avoided if at all possible in the fu- the downwind end of the roll cloud at the height of ture. The uniqueness of the Sierra Wave Project the mountain crest. Typical values encountered were stems from the fact that there appears to be no other 10ms_1 with the maxima of 15-25 m s_1 in extremely major meteorological field experiment that was or severe cases. Similarly, turbulence was found in two has been spearheaded by a sporting group. distinct layers downwind of the mountain range un- The Sierra Wave Project defines a transition stage der wave conditions: (i) as an omnipresent low-level in the technology of field experiments. In its concept, turbulence extending from the ground to -600 m design, organization, and execution it is an important above the mountain tops, with the highest degree of predecessor of modern mesoscale field experiments, turbulence encountered at the leading edge of a roll which had proved clearly that mesoscale phenomena cloud at about the level of the mountain crests, and could be studied effectively by combining high-den- (ii) an upper-level clear-air turbulence encountered sity ground-based and airborne observations. In the at levels above 10 km. One of the major contributions 1950s, however, data acquisition and logging systems of the Sierra Wave Project was to decisively deter- as well as computational resources were rudimentary. mine that the altimeter errors in flying over moun- Consequently, a period of several years after the tainous terrain were smaller than what was widely completion of the field operations was required to thought prior to the experiment. This finding was a complete the data reduction and analyses. This hard result of cancellation of two large sources of error in work was carried out at UCLA under Holmboe's su- the altimeter operation—a thermal and an inertial pervision by H. Klieforth, Holmboe's student who was one—producing the total error on the order of 100 m actively involved in both field phases. B. Woodward (maximum 300 m). Thus, what prior to the Sierra from SCSA and Einar Hovind, another graduate stu-

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC dent of Holmboe, were also involved in this major ef- tion of the theodolite tracking data to be completed fort. By the time the quality-controlled dataset was and the quality-controlled dataset to be obtained. This produced and the final reports written, the project appears to have left no time for work on those publi- had come to its end, and many of the Sierra Wave and cations before the end of the project and the expira- Mountain Wave-Jet Stream Project participants had tion of the Air Force funding. moved onto other jobs and new challenges. While an overview of this impressive experiment With this backdrop, it does not come as a complete and its findings on large-amplitude mountain waves surprise that the results of the experiment had more and rotors had appeared soon after the end of the impact on the aviation communities than they did on project in a WMO technical note (Queney et al. 1960), the meteorological scientific community. Aside from the general lack of publications in referred journals numerous technical reports and a few excellent "final" has caused the Sierra Wave Project to remain far less reports written by the UCLA and the Air Force Cam- known within the scientific community than other bridge Research Center staff, very few publications mountain wave investigations of much smaller scope, directly related to this project appeared in mainstream such as the field studies on the Colorado Front Range. scientific literature (e.g., Colson 1952; Long 1953a). As a result, it was the mountain waves of the Colo- This stood in contrast to the Thunderstorm Project, rado Front Range, such as the well-known case of which took place in 1946-47. Horace Byers was in 11 January 1972 (Lilly and Zipser 1972), and not those charge of that project, sponsored by the U.S. Weather generated by the Sierra Nevada, that had motivated Bureau. The final report of that project was compre- much of the subsequent theoretical and modeling hensive (U.S. Weather Bureau 1949) and bore great work on large-amplitude mountain waves. similarity to the final report for the Sierra Wave Project (Holmboe and Klieforth 1957). Yet, there OUTLOOK. The Sierra Wave Project and the sub- were complementary publications in the referred lit- sequent Mountain Wave-Jet Steam Project for the erature in the case of the Thunderstorm Project (Byers first time brought into focus large-amplitude moun- and Braham 1948; Byers and Hull 1949). One must tain waves and rotors. The relationship between the speculate as to the difference. two phenomena had sparked significant interest of re- In part the reason is that the Sierra Wave Project searchers in the 1950s (Queney 1955; Long 1955; had the flavor of a military science project, that is, one Scorer and Klieforth 1959; Kuettner 1959). This re- where specific operational objectives were at the fore- lationship was further investigated experimentally in front. In this case, it was the aviation safety hazards the late 1960s and early 1970s during the Colorado that were paramount, and producing reports for the Lee Wave Program (Lilly and Toutenhoofd 1969; Air Force had an absolute priority. Other reasons Lester and Fingerhut 1974). However, in the interven- appear to rest with the key UCLA project scientists, ing 30 yr there has been very little active interest in most notably with the project director Jorgen the subject in part because rotors, with their high Holmboe. Charged with a demanding task of admin- degree of intermittence and small spatial scale, are istering this ambitious field project and providing very dangerous and difficult to sample using in situ scientific oversight of the experiment, in addition to aircraft measurements. his regular teaching and administrative duties at With the latest advances in ground-based and air- UCLA, Holmboe was quite successful in his manage- borne remote sensing instrumentation, it has now rial role, producing high-quality reports that always become possible to document rotors, subrotor struc- reached the Air Force on time. Based on interviews tures, and zones of upper-level gravity wave break- with former students at UCLA (R. Terry Williams ing without attempting to penetrate these zones of 1992, personal communication; H. Klieforth 2002, severe turbulence with research aircraft (Ralph et al. personal communication; M. Wurtele 2002, personal 1997). Also, afforded by continuous advancements in communication), however, we know that Holmboe the field of high-performance computing, numerical was a perfectionist, a sometimes admirable trait, but simulations of rotors with nonhydrostatic mesoscale also a trait that often leads to hesitancy in publication. models are now becoming possible at high horizon- This might, in part, explain the absence of analytic dy- tal resolutions needed to numerically resolve them namical papers in the aftermath of the project. The (Clark et al. 2000; Doyle and Durran 2002). Thus, lack of publications on the observational part and the 50 yr after the launch of the Sierra Wave Project, re- comparison between theory and observations is likely visiting the mountain waves of the High Sierra with due to the exceedingly long period of time, much new ground-based and airborne remote sensors in a longer than originally expected, it took for the reduc- field experiment might be the key to unravelling the

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC underlying dynamical processes and relations be- Colson, D., 1952: Results of double-theodolite observa- tween large-amplitude mountain waves and rotors tions at Bishop, CaL, in connection with the "Bishop- (Grubisic and Kuettner 2004). Wave" phenomenon. Bull. Amer. Meteor. Soc., 33, 107-116. ACKNOWLEDGMENTS. The authors are indebted to Doyle, J. D., and D. R. Durran, 2002: The dynamics of Harold Klieforth, Joachim Kuettner, and Morton Wurtele mountain-wave-induced rotors. /. Atmos. Sci., 59, for sharing with us many illuminating recollections of the 186-201. Sierra Wave Project organization, events, and people. Forchtgott, J., 1949: Wave streaming in the lee of moun- Special thanks are due to Harold Klieforth for photos from tain ridges. Bull. Meteor. Czech., 3, 49. his personal collection, and for his continued interest in Fujiwara, S., 1927: Screwing structure of cloud. Quart. our project. Olivier Talagrand and Pierre de Felice, a long- J. Roy. Meteor. Soc., 53, 121-128. time assistant to Paul Queney, generously provided their Grubisic, V., and J. P. Kuettner, 2004: Sierra rotors and recollections of Paul Queney and his career. Philippe the Terrain-induced Rotor Experiment (T-REX). Drobinski's effort in providing us with a copy of Queney's Preprints, AMS 11th Conf. on Mountain Meteorology, 1936 papers is much appreciated. Jackie Jackson (DRI li- Mt. Washington Valley, NH, Amer. Meteor. Soc. brarian) is thanked for valuable technical assistance. Many [Available online at http://ams.confex.com/ams/ original reports from the Sierra Wave Project were ob- llMountain/techprogram/paper_77384.htm.] tained with the assistance of Harold Klieforth and Rob- Harper, K., 2004: The Scandinavian tag-team: Providers ert Sharman. We wish to thank all those who, in the course of atmospheric reality to numerical weather prediction of this work, had provided invaluable comments, includ- efforts in the United States (1948-1955). Proc. XXIInt. ing Joachim Kuettner, Harold Klieforth, and Hans Congress of History of Science, Mexico City, Volkert, who had reviewed earlier versions of the manu- Universidad Nacional Autonoma de Mexico, in press. script. Careful reviews by Ronald B. Smith, Richard Hoiland, E., 1951: Fluid flow over a corrugated bed. Ap- Scorer, and two anonymous reviewers were helpful in fur- pendix A. Air Force Cambridge Research Center Fifth ther improving our exposition of different aspects of the Progress Rep., Contract No. AF 19 (122)-263, 33 pp. Sierra Wave Project. This paper is based on the presenta- Holmboe, J., and H. Klieforth, 1954: Sierra Wave Project. tion given at the joint AMS Presidential Symposium on Department of Meteorology, UCLA Final Rep. Con- History of Atmospheric Science and the 12th Symposium tract AF 19(122)-263, 55 pp. on Meteorological Observations and Instrumentation in , and , 1957: Investigation of mountain lee February 2003. The first author's work on this project has waves and the air flow over the Sierra Nevada. been supported in part by the National Aeronautical and Department of Meteorology, UCLA Final Rep. Con- Space Administration EPSCoR Program, Grant NCC5- tract AF 19(604)-728, 283 pp. 397 (subaward UCCSN-99-899), and the National Science Kelvin, 1886: On stationary waves in flowing water. Foundation, Division of Atmospheric Science, Grant Philos. Mag., 5, 353-357, 445-452, 517-530. ATM-0242886. Knox, J. B., 1954: On waves of finite amplitude. Air Force Cambridge Research Center Scientific Rep. 5, Sierra Wave Project Contract No. AF 19 (122)-263, 25 pp. REFERENCES Krug-Pielsticker, U., 1942: Beobachtungen der hohen Abe, M., 1929: Cinematographic studies of rotary mo- Fohnwelle an den Ostalpen. Beitr. Phys. Atmos., 27, tion of a cloud mass near Mount Fuji. Bull. Cent. 140-164. Meteor. Observations, 7, 211-228. Kuettner, J. P., 1959: The rotor flow in the lee of moun- Byers, H., and R. Braham, 1948: Thunderstorm struc- tains. GRD Research Notes, No. 6, AFCRC-TN-58- ture and circulation. /. Meteor., 5, 71-86. 626, ASTIA Document No. AD-208862, 20 pp. , and E. Hull, 1949: Inflow patterns of thunder- , and F. Jenkins, 1953: Flight aspects of the mountain storms as shown by winds aloft. Bull. Amer. Meteor. wave. Air Force Surveys in Geophysics No. 35, Air Soc., 30, 90-96. Force Cambridge Research Center. Clark, T. L., W. D. Hall, R. M. Kerr, D. Middleton, Kiittner, J., 1938: Moazagotl und Fohnwelle. Beitr. Phys. L. Radke, F. M. Ralph, P. J. Nieman, and D. Levinson, Atmos., 25, 79-114. 2000: Origins of aircraft-damaging clear-air turbu- , 1939: Zur Entstehung der Fohnwelle. Beitr. Phys. lence during the 9 December 1992 Colorado Atmos., 25, 251-299. downslope windstorm: Numerical simulations and Lester, P. F., and W. A. Fingerhut, 1974: Lower turbu- comparison with observations. /. Atmos. Sci., 57, lent zones associated with mountain lee waves. /. 1105-1131. Appl. Meteor., 13, 54-61.

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Unauthenticated | Downloaded 10/11/21 06:24 AM UTC Lettau, H., 1990: The O'Neill experiment of 1953. , 1955: Rotor phenomena in the lee of mountains. Bound.-Layer Meteor., 50, 1-9. Tellus, 7, 367-371. Levin, S. M., 1997: Norwegians led the way in training , G. A. Corby, N. Gerbier, H. Koschmieder, and J. wartime weather officers. Eos, Trans. Amer. Geophys. Zierep, 1960: The airflow over mountains. WMO Union, 78. Tech. Note 34, 135 pp. Lewis, J., 1995: Le Roy Meisinger. Part I: Biographical Ralph, F. M., J. Neiman, T. L. Keller, D. Levinson, and tribute with an assessment of his contributions to me- L. Fedor, 1997: Observations, simulations and analy- teorology. Bull. Amer. Meteor. Soc., 76, 33-45. sis of nonstationary trapped lee waves. /. Atmos. Sci., , and L. Moore, 1995: Le Roy Meisinger. Part II: 54, 1308-1333. Analysis of the scientific ballooning accident of Rayleigh, 1883: The form of standing waves on the sur- 2 June 1924. Bull. Amer. Meteor. Soc., 76, 213-226. face of running water. Proc. London Math. Soc., 15, Lilly, D. K., and W. Toutenhoofd, 1969: The Colorado 69-78. lee wave program. Clear Air Turbulence and Its De- Scorer, R. S., 1949: Theory of waves in the lee of moun- tection, Plenum Press, 232-245. tains. Quart. J. Roy. Meteor. Soc., 75, 41-46. , and E. J. Zipser, 1972: The Front Range windstorm , 1987: Transcript of an interview with Professor of January 11, 1972—A meteorological narrative. R. Scorer. Interviewer: Professor P. Drazin. National Weatherwise, 25, 56-63. Meteorological Library, 29 pp. [Available from Long, R. R., 1953a: A laboratory model resembling the the National Meteorological Library, London "Bishop-Wave" phenomenon. Bull. Amer. Meteor. Rd., Bracknell, Berkshire RG12-2SZ, United Soc., 34, 205-211. Kingdom.] , 1953b: Some aspects of the flow of stratified flu- , and H. Klieforth, 1959: Theory of mountain waves ids. I. A theoretical investigation. Tellus, 5, 42-58. of large amplitude. Quart. J. Roy. Meteor. Soc., 85, , 1954: Some aspects of the flow of stratified fluids. 131-143. II. Experiments with a two-fluid system. Tellus, 6,97- U.S. Weather Bureau, 1949: The thunderstorm: Final 115. report of the Thunderstorm Project. U.S. Govern- , 1955: Some aspects of the flow of stratified fluids. ment Printing Office, 287 pp. III. Continuous density gradients. Tellus, 7, 342-357. von Karman, T., and L. Edson, 1967: The Wind and Be- Lyra, G., 1940: Uber den Einfluss von Bodenerhebungen yond. Little Brown & Co., 376 pp. auf die Stromung einer stabil geschichteten Whelan, R. F., 2000: Exploring the Monster. Mountain Atmosphare. Beitr. Phys. Atmos., 26, 197-206. Lee Waves: The Aerial Elevator. Wind Canyon Books, , 1943: Theorie der stationaren Leewellen-stromung x + 169 pp. in freir Atmosphare. Z. Math. Mech., 23, 1-28. Wurtele, M. G., 1953a: On lee waves in the interface sepa- Manley, G., 1945: The Helm Wind of Crossfell, 1937- rating two barotropic layers. Air Force Cambridge 1939. Quart. J. Roy Meteor. Soc., 71, 197-219. Research Center Scientific Rep. No. 2, Sierra Wave Meisinger, L., 1924: The balloon project and what we Project, Contract No. AF 19 (122)-263, 32 pp. hope to accomplish. Mon. Wea. Rev., 52, 27-29. , 1953b: The initial-value lee-wave problem for the Palm, E., 1955: Multiple-layer mountain wave models isothermal atmosphere. Air Force Cambridge Re- with constant stability and shear. Air Force Cam- search Center Scientific Rep. No. 3, Sierra Wave bridge Research Center Scientific Report No. 3, Con- Project, Contract No. AF 19 (122)- 263, 17 pp. tract No. AF 19 (604)-728. , 1953c: Studies of lee waves in atmospheric models Queney, M. P., 1936a: Recherches relatives a l'influence with continuously distributed static stability. Air du relief sur les elements meteorologiques (1). Force Cambridge Research Center, Scientific Rep. Meteorologie, 334-353. No. 4, Sierra Wave Project, Contract No. AF 19 , 1936b: Recherches relatives a l'influence du relief (122)-263, 10 pp. sur les elements meteorologiques (suite). , 1970: Meteorological conditions surrounding the Meteorologie, 453-470. Paradise Airline crash of 1 March 1964. /. Appl. Me- , 1947: Theory of perturbations in stratified currents teor., 9, 787-795. with application to air flow over mountain barriers. , R. D. Sharman, and A. Datta, 1996: Atmospheric Dept. of Meteorology, University of Chicago, Misc. lee waves. Ann. Rev. Fluid Mech., 28, 429-476. Rep. 23, 81 pp. , 1948: The problem of airflow over mountains: A summary of theoretical studies. Bull. Amer. Meteor. Soc., 29,16-26.

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