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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- or sailplane. In the pre-WWI period, glid- loon racing merged with 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 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 . 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 in Sudetes (then eastern Germany, to- the Sierra Wave Project, and it took place in two day southwestern ), the 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 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 was sparked in other European ment on the meteorological and 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 perturbations and air- the sailplane, but the earliest studies ofnote were flow modifications induced by this . 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 (Abe sic equations, assuming sinusoidal variation oforog- 1929). He paid particular attention to the rotary raphy and constant mean 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 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 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 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 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. The The Helm wind is a violently cold easterly project had both theoretical and observational pro- wind blowing down the western slope ofthe grams. Our discussion ofthe Sierra Wave Project Crossfell Range [N. Pennines, maximum al- is based largely on the comprehensive overview of ∼ titude 1km]...when the helm is blowing, the experiment by Holmboe and Klieforth (1957) a heavy bank ofcloud, the Helm Cloud, and Queney et al. (1960). Here we focus on the rests along the Crossfell Range, and at a impact ofthe 1951–1952 observational phase, dur- distance of three to four miles from the ing which large-amplitude mountain waves and ro- foot of the Fell, a slender, nearly stationary tors were explored in Owens Valley in the lee ofthe roll ofwhirling cloud, the Helm Bar, ap- Sierra Nevada. pears in mid-air and parallel to the Helm Cloud. The cold wind blows strongly down 4.1 Observational Techniques and Instrumentation the steep fell sides until it nearly comes un- der the Bar where it suddenly ceases...The In the 1951–1952 experimental campaign, the space between the Helm Cloud and Bar is main observational platform was a sailplane, most of usually quite clear although the rest ofthe them two-seater Pratt-Read, equipped with a clock, sky may be cloudy. altimeter, indicators for the rate-of-climb, airspeed Over a period ofseveral years (1937–1939), Man- and direction (), accelerometer, an outside ley painstakingly collected data from the ground on (fuselage) thermometer, and a barograph. In order the Helm wind and attendant meteorological fea- to produce a continuous record ofthe flight data, tures to develop a detailed description ofthe Helm the instrument panel was photographed at 1- or 2- wind phenomenon. He suspected (with the aid of second intervals on 16 mm film by two cameras in a limited number ofupper air observations) that the rear ofcockpit. The number ofmeasured physi- the Helm Cloud was associated with a strong inver- cal parameters and the recording system appears to sion and stable layer immediately above the Helm be quite modest compared to capabilities ofmodern Cloud. He also noted that on some occasions, not research whose data recording systems are only one, but as many as four or five standing waves capable ofrecording high-frequencydata (up to 10 were present downwind ofthe mountains—equally Hz) for dozens of variables simultaneously and even spaced at distances ofabout 4 miles. The Helm Bar, displaying them during the flight. Yet this system a rotor cloud, was also observed as a regular feature afforded the Sierra Wave researchers with a contin- positioned not too far from the foot of the range. uous record ofsailplane flights forthe post analysis. The WWII brought intensive field investigation of The total flight time ofthe sailplane was limited mountain waves to an almost complete standstill. to 4.5 hours by the oxygen supply, and the tracking During the 1940s only a few smaller field investi- operation was limited by the film length to 1.5 hour. gations took place, most notable among them the The tracking ofsailplanes fromthe ground was field studies by Krug-Pielsticker (1942) in the east- carried out by a network of3 photo-theodolites, ern , and F¨orchgott (1949) in the mountains of, a radar and a Raydist (all-weather radio location) then, Czechoslovakia. The 1950s announced a new system. The instruments were manually operated era in the mountain wave field investigation that in tracking the sailplanes but the readings ofthe started with the Sierra Wave Project in the United photo-theodolites and the radar were photographed States. 2The Navy pulled out of the Sierra Wave Project during 1951 because of demands of other higher priority research.

3 simultaneously and automatically at 5-second inter- 4.1 Major Observational Findings vals on 35 mm film. The Raydist tracking system produced electronic signals which were recorded di- Mountain waves observed over the Owens Valley rectly. Compared to the automatic inertial navi- by the Sierra Wave researchers were classified into gation system (INS) and GPS tracking systems on three categories: board of modern research aircraft, the methods for determining the position ofsailplanes used by the 1. Strong Waves with wavelengths of13–32 km, Sierra Wave researchers were painstakingly com- 1,200–2,400 m maximum altitude variation of ± plex. Due to the limitations ofboth the ground a streamline, and vertical wind speed of 9to ± −1 tracking and the data recording system onboard 18ms . As stated in Holmboe and Klieforth sailplanes, useful data were obtained in only 50% (1957) “the near-legendary reputation ofthe ofthe conducted research flights in the 1951-1952 Sierra Wave derives from the spectacular phe- season (11 research flights on 9 different days). nomena associated with the lee waves ofstrong The corrected quantities derived from the air- intensity”. An example ofa strong wave is il- borne measurements alone and their estimated ac- lustrated in Fig. 1, ± curacies were: i) time ( 0.5 s), ii) pressure alti- 2. Moderate Waves with wavelengths of8–13 km, ± ± tude ( 12 m at MSL to 30 m at 12,000 m), iii) 600–1,200 m maximum altitude variation ofa ± −1 ± true air speed ( 1ms ), iv) heading ( 3 deg), streamline, and vertical wind speed of ±4.5 to ± −1 v) sinking speed ( 0.1 m s ), and ±9ms−1,and (± 1.5◦ C). The synthesis oftracking and airborne data, in which assumptions ofsteady state and two- 3. Weak Waves with wavelengths of4–8 km, 150– dimensionality in a coordinate plane perpendicular 600 m maximum altitude variation ofa stream- to the Sierra crest were introduced, produced the line, and vertical wind speed of ±1.5 to ±4.5 m following physical quantities at estimated accura- s−1, marginally strong to support a sailplane. cies: i) horizontal component ofwind perpendicular to the Sierra crest (± 5%), vertical wind speed (± 5%), (± 2◦ K), and D-value (i.e., altimeter correction) (± 30 to ± 60 m). Other sources ofdata included the following:

(a) Radiosonde ascents from Lodgepole, Sequoia, and Merced upwind ofthe Sierra crest,

(b) Still photographs and time-lapse films, from air and from the ground, of the Sierra Wave clouds,

(c) Surface measurements from recording in- struments (barographs, thermographs, and anemographs) from a number of points across Owens Valley, the eastern Sierra and the west- ern Inyo slopes,

(d) Surface measurements from mobile observa- tions (altimeter, aneroid barometer, thermome- Figure 1: Results from the Sierra Wave Project. ter, anemometer, and photo cameras) across Streamlines in a strong mountain wave and “nor- the Owens Valley, mal” rotor on 16 February 1952. Dashed lines (with- out arrows) show the sailplane trajectory projected (e) Meteograph flights made by the aircraft used onto a west-to-east vertical cross-section perpendic- for sailplane towing, ular to the axis ofthe Owens Valley near Indepen- dence (from Holmboe and Klieforth 1957). (f) Double-theodolite pilot-balloon ascents made by the Weather Bureau at the Bishop Airport Rotors and zones oflow-level were fre- in Owens Valley, and quently found beneath strong mountain lee waves (cf. Fig. 1). Two basic types of rotor clouds were (g) Weather logs and synoptic data. identified by the Sierra Wave investigators: i) a

4 “normal” rotor cloud associated with lee waves 4.3 Contributions to Aviation Safety paralleling the topographic divide and following its bends, and ii) a severe rotor cloud forming a One ofthe major accomplishments ofthe Sierra straight, almost vertical wall a considerable distance Wave Project was the formulation of the aviation downstream from the base of the lee slope. In the safety hazards associated with flying in mountain- latter case there is no apparent trailing edge to the ous terrain, and their widespread circulation within rotor, the cloud extends eastward over the White the soaring communities in the U.S. and abroad. and Inyo Mountains, and the flow is similar in ap- The latter is not surprising given the pivotal role pearance to a (Kuettner 1959). the California Soaring Association pilots played in this experiment. 4.2 Major Theoretical Accomplishments The combined phenomenon ofwave and rotor flows was found to present serious hazards to avia- From the early contributions on the theory tion. In the order ofseverity, these hazards were: ofmountain waves by Queney (1936) and Lyra i) downdrafts, ii) turbulence, iii) local change of (1940, 1943), the theoretical treatment ofmountain upper-level , and iv) altimeter errors. waves had been considerably advanced by Queney The most significant areas ofdowndraftwere (1947, 1948) and Scorer (1949) during the late found on the lee slope of the mountain range and 1940s. Analytical or semi-analytical steady-state the downwind end ofthe rotor cloud at the height solutions, both hydrostatic and nonhydrostatic, for ofthe mountain crest. Typical values encountered flow over two-dimensional orography for atmosphere were10ms−1 with the maxima of15 to 25 m s −1 with constant mean wind and stability and a two- in extremely severe cases. Similarly, turbulence was layer atmosphere with constant but differing val- found in two distinct layers downwind of the moun- ues ofwind speed and stability in each layer, had tain range under wave conditions: i) as the om- already been known before the start of the Sierra nipresent low-level turbulence extending from the Wave Project. ground to ∼600 m above the mountain tops, and The observational campaigns ofthe Sierra Wave ii) the upper-level clear-air turbulence. One ofthe Project had, however, provided new impetus for the major contributions ofthe Sierra Wave Project was theoretical work on mountain waves. The theoret- to decisively determine that the altimeter errors in ical program ofthe Sierra Wave Project was based flying over mountainous terrain were smaller than at UCLA where it had involved Holmboe, H¨oiland, what was widely thought prior to the experiment. Knox, and Wurtele. Some theoretical work was also This finding came as a result ofcancellation oftwo carried out by Kuettner at the Cambridge Air Force large sources oferror, a and an inertial one, Research Center, as well as by Queney at the Uni- producing the total error on the order ofhundred versity ofParis, and Palm, Foldvik and Fjortoft meters (maximum 300 m). at the University ofOslo, Norway who all visited UCLA on several occasions. 5. SUMMARY AND CONCLUSIONS Ofthe UCLA group, the most significant contri- butions came from Morton Wurtele who had intro- The confluence ofinterest in mountain waves duced vertical in the previously studied by the soaring community and several scientific in- steady-state, two-dimensional, one- and two-layer vestigators was the stimulus for the Sierra Wave atmospheric models (Wurtele 1953a). The two- Project. With little doubt, the primary impetus layer model, with a Couette-flow (constant shear, came from the Southern California Soaring Asso- constant stability) in the troposphere, and uniform ciation and its contingent that flew the Bishop , which was motivated in part by the Wave. Funding for research, however, demanded observed atmospheric structure upwind ofthe Sierra that an academic component be added and thus the Nevada, was particularly successful in reproducing UCLA team headed by Jorgen Holmboe entered the the observed wavelengths for a number of strong project. There appears to be no other major me- wave cases from the Sierra Wave Project. This teorological field experiment that was or has been model was further extended by Palm (1955) to in- spearheaded by a sporting group. With this back- clude multiple layers. Wurtele also made a contri- drop, it does not come as a complete surprise that bution to the solution ofthe initial-value problem the results ofthe experiment had more impact on for airflow over corrugated bed (Wurtele 1953b,c), the soaring community than it did on the scientific continuing the earlier work ofH¨oiland (1951). community. Aside from numerous technical reports and a few excellent “final” reports written by the

5 UCLA and the Air Force Cambridge Research staff, ofMeteorology, UCLA, Contract AF 19(604)– very few publications in the mainstream scientific 728, pp. 283. literature came out ofthis project. Lyra’s (Lyra 1943) and Queney’s (Queney 1947) von Karm´an, T., (with L. Edson), 1967: The Wind theoretical work went far to lay the solid foundation and Beyond. Little Brown & Co., 376 pp. for the interpretation of analyses that came from the Kelvin, 1886: On stationary waves in flowing wa- project. Holmboe’s contribution to the theory was ter. Philos. Mag., 5, 353–357, 445–452, 517– minimal, although he is certainly credited with sci- 530. entific oversight ofthe experiment. The reason for his limited theoretical contribution is difficult to un- Krug-Pielsticker, U., 1942: Beobachtungen der ho- ravel. We can only speculate that his “perfectionist” hen F¨ohnwelle an den Ostalpen. Beitr. Phys. approach to meteorology and an enamorment with frei. Atmos., 27, 140–164. simple analytic theory, did not lend itselfto explain- ing aspects ofthe Bishop Wave that went beyond Kuettner, J., 1938: Moazagotl und F¨ohnwelle. 25 earlier rather comprehensive work. However, it was Beitr. Phys. frei. Atmos., , 79–114. another theoretician from the UCLA team, Morton Kuettner, J., 1939: Zur Entstehung der F¨ohnwelle. Wurtele, who had made significant contributions to Beitr. Phys. frei. Atmos., 25, 251–299. the theoretical advancement ofthe field as a result ofhis involvement in the Sierra Wave Project. Kuettner, J. P., 1959: The rotor flow in the In many ways, the project had the flavor ofa lee ofmountains. GRD Research Notes, No. military science project, i.e., one where specific op- 6, AFCRC–TN–58–626, ASTIA Document No. erational objectives were at the forefront. In this AD–208862, pp. 20. case, it was the safety of the military aircraft that was paramount. Wartime loses ofaircraftin moun- Lettau, H., 1990: The O’Neill experiment of1953. 50 tainous terrain needed to be understood and simi- Boundary-Layer Meteor., , 1–9. lar accidents avoided ifat all possible in the future. Lewis, J., 1995: Le Roy Meisinger. Part I: Bi- Publication ofscientific results in the refereedlit- ographical tribute with an assessement ofhis erature is often secondary in these projects as was contributions to meteorology. Bull. Amer. Me- the case in the exploration ofradioactivity in the teor. Soc., 76, 33–45. atmosphere following nuclear detonation during the 1950s (Stockwell and Lewis 2001). Lewis, J., and L. Moore, 1995: Le Roy Meisinger. Part II: Analysis ofthe scientific ballooning ac- cident of2 June 1924. Bull. Amer. Meteor. 4. REFERENCES Soc., 76, 213–226. Lyra, G., 1943: Theorie der station¨aren Leewellen- str¨omung in freir Atmosph¨are, Zeit. angew. Abe, M., 1929: Cinematographic studies ofrotary Math. Mech., 23, 1–28. motion ofa cloud mass near Mount Fuji. Bull. Cent. Meteor. Obs., 7, 211–228. Manley, G., 1945: The Helm Wind ofCrossfell, 1937–1939. Quart. J. Roy. Meteor. Soc., 71, F¨orchtgott, J., 1949: Wave streaming in the lee of 197–219. mountain ridges. Bull. Met. Czech., Prague, 3, 49. Meisinger, L., 1924: The balloon project and what we hope to accomplish. Mon. Wea. Rev., 52, Fujiwara, S., 1927: Screwing structure ofcloud. 27–29. Quart. J. Roy. Meteor. Soc., 53, 121–128. Palm, E., 1955: Multiple-layer mountain wave H¨oiland, E., 1951: Fluid flow over a corrugated models with constant stability and shear. Sci- bed. Appendix A, Fifth Progress Report, Con- entific Report No. 3, Contract No. AF 19 tract No. AF 19 (122)–263. Air Force Cam- (604)–728. Air Force Cambridge Research Cen- Research Center, Cambridge, Mass. ter, Cambridge, Mass.

Holmboe, J. and H. Klieforth, 1957: Investigation Queney, M. P., 1936a: Recherches relatives ofmountain lee waves and the air flow over a l’influence du reliefsur les ´ el´ements the Sierra Nevada. Final Report. Department m´et´eorologiques (1), Meteorologie, 334–353.

6 Queney, M. P., 1936b: Recherches relatives a l’influence du reliefsur les ´ el´ements m´et´eorologiques (suite), Meteorologie, 453–470.

Queney, M. P., 1947: Theory ofperturbations in stratified currents with application to air flow over mountain barriers, The University of Chicago Press, Misc. Report. No. 23.

Queney, M. P., 1948: The problem ofairflow over mountains: A summary oftheoretical studies, Bull. Amer. Meteor. Soc., 29, 16–26.

Queney, M. P., G. A. Corby, N. Gerbier, H. Koschmieder, J. Zierep, 1960: The airflow over mountains. WMO Tech. Note No. 34. 135 pp.

Scorer, R. S., 1949: Theory ofwaves in the lee of mountains, Quart. J. Roy. Meteor. Soc., 75, 41–46.

Stockwell, W., and J. Lewis 2001: Is radioactivity a forgotten component of atmospheric chem- istry?: A perspective on Edward Martell’s ca- reer. Preprints. Millennium Symposium on At- mospheric Chemistry: Past, Present, and Fu- ture ofAtmospheric Chemistry, 14–19 January 2001, Albuquerque, NM, Amer. Meteor. Soc., Paper 1.2, 4 pp.

Wurtele, M. G., 1953a: Studies oflee waves in atmospheric models with continuously dis- tributed static stability. Scientific Rep. No. 4, Sierra Wave Project, Contract No. AF 19 (122)-263. Air Force Cambridge Research Cen- ter, Cambridge, Mass.

Wurtele, M. G., 1953b: The initial-value lee-wave problem for the isothermal atmosphere. Scien- tific Rep. No. 3, Sierra Wave Project, Contract No. AF 19 (122)-263. Air Force Cambridge Re- search Center, Cambridge, Mass.

Wurtele, M. G., 1953c: On lee waves in the in- terface separating two barotropic layers. Final Report. Sierra Wave Project. Scientific Rep. No. 2, Contract No. AF 19 (122)-263. Air Force Cambridge Research Center, Cambridge, Mass.

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