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BERNHARD HAURWITZ August 14, 1905-February 22, 1986 BY JULIUS LONDON BERNHARD HAURWITZ WAS AN unusually productive physical scientist en c! educator throughout his aclult life. His principal scientific interests en c! accomplishments were in the area of dynamic meteorology, that is, the application of mathematics en c! Quit! dynamics to all scales of atmospheric motions. In aciclition to his many basic contributions to the study of short-perioc! atmospheric wave motions, planetary waves, inclucling atmospheric ticles, en c! vortex motions in tropical cyclones, he wrote important papers on such sub- jects as atmospheric racliation, wave structure of noctilu- cent cloucis, en c! attempts to document internal ticles in the oceans. The main directions of his work were in both ana- lytic en c! diagnostic investigations of the structure en c! mo- tions of the atmosphere. Although primarily a theoretician, Haurwitz enjoyed work- ing with observer! atmospheric en c! oceanic ciata. His analy- ses were always clirectec! towarc! gaining insight into the physical structure en c! important physical processes in the atmosphere. This was already evident in his Ph.D. thesis on the relations between changes of atmospheric pressure en c! temperature and continued throughout his research career. In general, he preferred writing short papers, with the idea 87
88 B I O G RA P H I C A L EMOIRS that they would be more apt to be read than Tong ones. At the memorial for Haurwitz at the National Center for At- mospheric Research (NCAR), Philip Thompson, who had an almost continuous association with him for about forty years, commented, 1 gradually came to realize that the range of Bernhard's interests and contributions spanned virtually the whole range of atmospheric science." His role as an educator went beyond the more than fifty years he spent in active involvement at different academic institutions. Two of his textbooks were still listed in the Science Citation Index covering the five-year period of 1988- 92. EARLY YEARS Bernhard Haurwitz was born in GIogau, Germany, in 1905, to upper-middle-class parents. His father, Paul Haurwitz, was a reasonably successful merchant in the city. He had a younger sister, Ilse, who was born in ~ 907. While still a teenager, he developed an interest in astronomy and, to- gether with his friend Wolfgang Gleissberg, became a coop- erative solar observer, sending sunspot information to the central solar observatory in Zurich, Switzerland. This inter- est in solar phenomena stayed with him through his entire professional life. . --a Haurwitz completed his Gymnasium (high school) stud- ~es, specializing in classical languages (Latin and Greek) and in mathematics and physics. In ~ 923, at the age of eighteen, he enrolled at the University of BresTau, where he spent one and a half years before going on to the Univer- sity of Gottingen where he studied mathematics, physics, and geophysics. In Gottingen he took courses from Richard Courant, Richard Frank, Emil Wiechert, and others. It was during that time that he developed an interest in meteorol- ogy as a result of preparing to present a seminar in his
B E R N H A R D H A U RW I T Z 89 course in geophysics. The paper he reviewoc! was on the subject of atmospheric waves written by Ludwig Weickmann, then professor of geophysics at the University of Leipzig. He cleciclec! to apply to Professor Weickmann to write his Ph.D. thesis at the Geophysical Institute in Leipzig en c! was soon accepted. Haurwitz arriver! at the University of Leipzig in 1925 en c! began work on his thesis uncler Weickmann's direction. The thesis macle use of then-available ciata from self-registering atmospheric souncling balloons. (Racliosoncle observations became available only after their clevelopment in the late 1920s.) His thesis was motivates! by observations that weather systems tenclec! to move along with patterns of large sur- face-pressure changes. Haurwitz's results inclicatec! that an atmospheric pressure decrease at the surface, accompanies! by a surface-temperature increase, is associates! with a pres- sure increase at levels near the tropopause, a relation to be anticipates! if hydrostatic conditions obtain. This effect wouIc! suggest the existence of a layer in micitroposphere where the wine! field! was geostrophic en c! thus nondivergent, an important assumption macle in the late 1940s at the time of early numerical weather precliction efforts as applier! to two- climensional flow at 500 mb. After completing his dissertation (1927) en c! his seconc! (habilitation) thesis ~ ~ 93 ~ ), Haurwitz became a lecturer at the University of Leipzig. It was there that he first heart! guest lectures from the early British en c! Scandinavian pio- neers in atmospheric en c! ocean dynamics namely, Lewis F. Richardson, Vilhelm Bjerknes, en c! Haralc! U. Svercirup. Haurwitz was impressed with the lectures en c! subject mat- ter presented en c! arranger! for a three-month visit to Osio en c! Bergen in early 1929. Thus, he conic! interact with me- teorologists who were in the forefront of research in geo- physical fluid dynamics (Oslo) and synoptic meteorology
go B I O G RA P H I C A L EMOIRS (Bergen). This research was of particular interest to him since his own studies at that time involves! methods of solv- ing the highly nonlinear problems of wave motions in the atmosphere en c! oceans by a simplification process baser! on perturbation approximations to the nonlinear equations. This technique continues! to be user! extensively before nu- merical methods of solution were practical as a result of the clevelopment of high-speec! computers. IncleecI, up to that time, applier! mathematicians wouIc! quip that there were two types of clifferential equations linear en c! nonsolvable! In an article written for the Compendium of Meteorology in 1951, Haurwitz reviewoc! the rationale for the use of the perturbation equations as a methoc! of getting closecI-form solutions to problems in atmospheric dynamics. During his stay in Norway, Haurwitz spent most of his time working on problems of fluic! dynamics with Scanclina- vian colleagues Halvor Solberg en c! H. U. Svercirup en c! with a young student at that time, {organ Holmboe, with whom he frequently went skiing. As a matter of fact, one of the attractions for his Norwegian visit was the increaser! opportunity for cross-country skiing and mountain hiking, which were his favorite sports. These interests certainly playact a nontrivial role some thirty years later in his decision to move to BouIcler, Coloraclo. While in Osio he also occasionally visited with Car! Stormer, who was involved in a program of observations of the height of occurrence en c! main features of the polar aurora. This experience clearly contributes! to his later interests en c! re- search applier! to upper-atmosphere phenomena. Upon his return from Norway, Haurwitz continues! to work on the problem of wave motions in a compressible fluicI, the general area of his main interest when he came to the Geophysical Institute in Leipzig. He user! this subject for his "Habilitationsschrift." His research quickly became
B E R N H A R D H A U RW I T Z 91 focuses! on the problem of short-wave "billow" cloucis that appear at the interface of a two-layer moclel in the atmo- sphere (or oceans). By introducing assumptions of inhomo- geneity, stratification, compressibility, en c! wine! shear across the interface, Haurwitz was able to get goof! agreement between theory en c! observations of the billow clouc! wave- lengths en c! periods. He returnee! to this problem off en c! on over the next forty years en c! extenclec! his moclel appli- cations in an attempt to explain waves associates! with noc- tiTucent cloucis. After completion of his thesis en c! professional examina- tion, Haurwitz became a lecturer at the University of Leipzig. During the next two years he gave a set of three courses in atmospheric physics: atmospheric acoustics, meteorological optics, en c! atmospheric racliation. Haurwitz then felt that it wouic! be interesting to spenc! some time abroad, en c! at the invitation of CarI-Gustaf Rossby, who was then associate professor at the Massachusetts Institute of Technology, he came to the Uniter! States in 1932 for what was supposes! to be a relatively brief seven-month visit. PROFESSIONAL ACTIVITIES IN THE UNITED STATES AND CANADA (1932-41) Bernharc! Haurwitz arriver! in the Uniter! States in Octo- oer 1932 to share a temporary appointment at MIT en c! the Blue Hill Observatory of Harvard. He cliviclec! his time be- tween giving a series of lectures at MIT on problems re- latec! to the integration of the atmospheric perturbation equations and a research program at the Blue Hill Observa- tory involving, among other things, analysis of solar raclia- tion ciata en c! their use in determination of atmospheric turbidity. Among the graduate students at MIT who attenclec! his lectures en c! who later macle significant contributions in
92 B I O G RA P H I C A L EMOIRS meteorology en c! oceanography were Harry WexTer, Jerome Namias, Athelstan Spilhaus, en c! Raymonc! Montgomery. During his stay in the Boston-Cambricige area, he also worker! on a problem that hac! intrigues! him for some time. In the absence of high-flying aircraft or other practical meth- ocis of measuring the micitropospheric pressure in en c! arounc! hurricanes, it hac! commonly been assumer! that tropical cyclones extenclec! only to heights of about 2 to 3 km above the ocean surface. No one up to that time hac! attemptec! to determine the vertical extent of these storms, that is, the height at which the pressure wouIc! be horizontally uni form. Haurwitz assumer! that atmospheric columns near the center en c! the outer part of the storm are each in approximate hydrostatic equilibrium en c! that the vertically averages! mean temperature near the center of the storm is warmer than that at the outer part. He was then able to show that the level of the pressure equalization the height of uniform pressure arounc! the storm was approximately 10 km. This height range was, of course, substantially veri- fiec! as both direct en c! indirect measurements became avail- able. Moreover, he was also able to show that the shape of the eye of the storm approximates! that of a funnel, as verified by later observations. In early 1933 Haurwitz acceptec! an invitation from the seismologist Beno Gutenberg, a former colleague in Ger- many, to visit the California Institute of Technology in Pasa- clena where he gave lectures on atmospheric dynamics. Among the attendees at these lectures was Albert Einstein, who hac! just come from Berlin to spenc! the winter at CalTech. A short time after Haurwitz's arrival at Pasadena, Adolf Hitler was appointee! chancellor of the German Reich. Both Haurwitz en c! Einstein inclepenclently chose not to return to Germany. Haurwitz decided that when his visitor's visa expires! he wouic! apply for a visa extension en c! investi
B E R N H A R D H A U RW I T Z 93 gate the possibility of a position in Canada. He was able to get a research appointment in the physics department at the University of Toronto through a Carnegie Institution grant. However, it took two years, until the summer of 1935, before the clerical rec! tape was straightenec! out. Mean- while, he spent those two years continuing his lectures en c! research at MIT en c! the Blue Hill Observatory. In 1934 he marries! Eva Schick, who hac! clone her aca- clemic studies in Germany in physics before immigrating to the Uniter! States. They went to Toronto in 1935 where he worker! at the University of Toronto en c! the Canaclian Me- teorological Service for the next six years before they re- turnec! to the Uniter! States in 1941. Haurwitz came to Toronto as a Carnegie Institution fel- low (1935-37) in the physics department at the University of Toronto en c! continues! as a visiting lecturer in the cle- partment until 1941. When the Carnegie fellowship enclecI, he took a position as meteorologist with the Canaclian Me- teorological Service (1937-41~. The Canaclian Service hac! set up a cooperative meteorological training program with the physics department at the University of Toronto, en c! each year he gave a regular graduate course in dynamic meteorology. In aciclition, he presented a series of eight lectures at the university on the subject of "The Physical State of the Upper Atmosphere." The lectures were basecI, in part, on the course he gave while he was at the Univer- sity of Leipzig. They were publisher! as a series in the iour- nal of the Royal Astronomical Society (Canacia) en c! as a special short book in 1937. Although the material in that book is now almost completely out of ciate, it was the first book of its kind and summarized what was then known about the "upper atmosphere." A second edition was published in 1941, when a large-scale meteorological training program was started during the early period of World War II.
94 B I O G RA P H I C A L EMOIRS By 1940 there was also increased need for a new English- language textbook on dynamic meteorology. This gave Haurwitz the opportunity to refine en c! Alit his lecture notes. His book, Dynamic Meteorology, was also publisher! in 1941, at the time of the rapic! increase in the training of meteo- rologists in the Uniter! States cluring WorIc! War II. The book was wiclely user! as a stanciarc! textbook on dynamic meteorology for the next twenty years. The meteorology program at the University of Toronto was also user! to train people newly hirer! by the Canaclian Meteorological Service. As a result, Haurwitz spent consicI- erable time in Toronto preparing eclucational programs for weather forecasters en c! instructional booklets for the Brit- ish Commonwealth Air Training Plan. In ~ 938 Eva gave birth to their son, Frank. (At the time Bernharc! was giving a lecture at the university.) When WorIc! War II starter! in 1939, Haurwitz, who still hell! a German passport, was cIassifiec! as an "enemy alien" en c! hac! to report to the Royal Canaclian Mounter! Police once a month. But after a brief backgrounc! check, that requirement was liftecI. Being an enemy alien, however, clic! not interfere with his having access to the "secret" weather cocles clevelopec! for use at that time or his being involves! with coordinating the joint use of these cocles by the me- teorological services of the Uniter! States en c! Canada. Despite all of these academic en c! semiaciministrative clu- ties, he still macle time to work on a number of research problems, inclucling funciamental studies of the motions of large-scale atmospheric disturbances. The latter resulted in three publications during the period 1937-40 that are still consiclerec! classic in the fielc! of planetary waves in the atmosphere. Haurwitz's study of planetary waves stemmed from his early interest as a graduate student in the theory of solar
B E R N H A R D H A U RW I T Z 95 inclucec! atmospheric ticles. The original motive for the 1937 paper, "The Oscillations of the Atmosphere," was to fins! an explanation for resonance of the solar semicliurnal pres- sure ticle. However, the emphasis on that paper was on the class of planetary waves whose periods are long comparer! to a siclereal clay en c! move westwarc! relative to the mean zonal flow in which they are embeciclecI. It was in that paper that Haurwitz derived the speed of low-frequency nondi- vergent planetary waves on a spherical earth that are typi- cal of large-scare meteorological systems. An analogous re- sult was clerivec! by Rossby en c! collaborators in 1939 for the speec! of long waves in micIlatitucles baser! on the assump- tions that the air motion was horizontal en c! nondivergent on a plane earth with no lateral shear in the basic westerly current. Only the latituclinal variation of the Coriolis pa- rameter was consiclerecI, en c! the wave motion was assumer! to be purely zonal. These waves are known as Rossby waves. In the two papers Haurwitz published in 1940, "The Mo- tion of Atmospheric Disturbances" en c! "The Motion of At- mospheric Disturbances on a Spherical Earth," he extenclec! the work of Rossby et al. en c! also reclerivec! the formal results of the paper he publisher! in 1937 to show direct application of the results to the observer! "centers of ac- tion" of the northern hemisphere mean circulation system. Haurwitz moclifiec! Rossby's assumptions to inclucle the mericlional extent of the wave, the effects of friction en c! of baroclinic forcing as, for instance, with zonal flow across a north-south coastline. His results indicated that the impor- tance of the latitucle variation of the Coriolis force (,8 ef- fect) on the wave speec! clecreasec! as the lateral extent of the disturbance became smaller. He also fount! that, when the effect of friction is applier! to the perturbec! flow, the amplitude of the disturbance decreases exponentially with time.
96 B I O G RA P H I C A L EMOIRS In aciclition, he shower! that the effect of imposing a Ton- gituclinally fixer! external force on the flow pattern, such as a lancI-ocean interface, generates stationary waves of ap- proximately the same wavelength as the free oscillation of the system. This latter result was subsequently shown in the literature to apply as well to imposer! fixer! external forcing on planetary waves associates! with north-south orographic surface features. The treatment of these horizontal plan- etary waves on a rotating spherical earth as clevelopec! in the two papers by Haurwitz in 1940 has given rise to the identification of this general class of waves as Rossby-Haurwitz waves, en c! they are so referrer! to in the literature. In 1940 Sverre Pettersson, then chair of the Department of Meteorology at MIT, visitec! the Meteorological Service in Canada. He hac! known Haurwitz from the time when they were both in Norway. He invites! Haurwitz to come back to the department at MIT, en c! in July 1941 Bernharc! returnee! to Cambridge, this time as associate professor of meteorology. At the same time, Bernhard received an ap- pointment as Abbott Lawrence Rotch Research Fellow at Harvard's Blue Hill Observatory. When Haurwitz arriver! at MIT in micI-194l, the clepart- ment was already involved in the Army Air Corps/Navy ad- vanced training program in meteorology. (MIT was then one of five universities participating in the national pro- gram that eventually trainee! over 10,000 weather officers.) While at MIT, Bernhard's principal academic responsibili- ties were to teach a course on dynamic meteorology and a course clearing with the physical principles of climate. The latter course lee! to the publication of a textbook, Ctimatol- ogy, coauthored! with his colleague James Austin. At the time of his return to Cambridge, the Uniter! States was not yet at war and Bernhard's official immigration sta- tus was as a "neutral alien." However, when the United States
B E R N H A R D H A U RW I T Z 97 enterer! the war on December 7, 1941, he again became an "enemy alien." Early in 1942 a representative of the Army Air Force (formerly Army Air Corps) asker! him to conduct a research program on Tong-range weather forecasting that was baser! on statistical techniques trier! a clecacle earlier in Germany. The project was labeler! as secret, en c! since Ber- narc! was ciassifiec! as an enemy alien, he was only able to supervise the program as the unofficial director. As he hac! anticipated, the results of the suggestec! technique shower! no particular forecasting skill, but it clic! give him the op- portunity to work with two very bright, young weather offic- ers who hac! just completec! the meteorology course Rich- arc! Craig en c! Edward! Lorenz who remainec! colleagues en c! friends of his for a long time afterward. During this time his research clealt with problems of atmospheric fluic! dynamics, atmospheric racliation, ant! possible solar-weather relations. One of the more notable of the Quit! dynamic studies involves! a continuation of some of the problems clealt with in his habilitation thesis on the theory of wave motion in a stratifies! fluid. Waves in the atmosphere that give rise to clouc! bancis or billow cloucis may occur as a result of convective patterns where the in- stability clue to atmospheric stratification is an important factor in their clevelopment, or they may be a manifestation of internal waves that result from vertical win c! shear across a surface of density discontinuity or within a shallow transi- tion region. In a paper he publisher! in 1947, he concluclec! that convection patterns en c! internal wave patterns are "largely one en c! the same phenomenon." Haurwitz's return to the Cambricige-Boston area also pro- viclec! him with the opportunity to resume his past associa- tion with Hurt! Willett en c! other colleagues en c! friends at MIT en c! the Blue Hill Observatory. At Blue Hill he ex- tenclec! some of his earlier studies of observer! solar irracli
98 B I O G RA P H I C A L EMOIRS ance to clevelop empirical relations between solar irracli- ance measurements at the earth's surface en c! synoptic re- ports of total cloucliness en c! clouc! type. He reasoner! that, if such relations were fount! to be statistically reliable, they conic! be user! to derive information on the solar irracliance at the surface in the absence of such measurements be cause total cloucliness en c! clouc! type information was nor- mally available from routine weather reports. The results of these studies have been user! as historic references in re cent years as more direct information on the clepenclence of clouc! transmittance as a function of clouc! type has been clerivec! from satellite en c! surface observations. Haurwitz's renewoc! association with the Blue Hill Obser- vatory en c! its director, Charles F. Brooks, also reviver! an earlier interest of his on solar variability en c! its possible effect on the Tower atmosphere. Most publisher! studies on this subject were confiner! to statistical analyses of such pos- sible solar relations. He felt that this approach was inacI- equate en c! states! that "when looking for empirical proofs of the connection between solar activity en c! weather, it is imperative to have a clear picture of the physical cause of the relation to be establishecI." Although it was well known from both observations en c! theory that solar perturbations resultec! in disturbances in the high atmosphere, he thought it important to provicle a plausible physical mechanism by which anomalous solar behavior conic! either clirectly or nclirectly affect the lower atmosphere in an observable fash- on. In 1948 Haurwitz qualitatively outlined such a proposed mechanism based on a physical-dynamic model of how a solar eruption could influence the pressure distribution in the troposphere. He postulates! that the initial disturbance conic! come from increaser! ultraviolet racliation associates! with a short-lived solar flare. This energy would be absorbed
B E R N H A R D H A U RW I T Z 99 by ozone in micistratosphere over subsolar (equatorial) lati- tucles. Then in a simplifier! moclel he shower! that the re- sultant heating wouIc! produce a net polewarc! air flow in the stratosphere that wouic! result in a temporary reduction in the surface pressure at low latitucles en c! thus affect the low-tropospheric wincis in the tropics. He later abanclonec! this mocle! when observations inclicatec! that his initial as- sumec! solar energy perturbation was much too high, by orders of magnitude, en c! it was not possible to detect any of the preclictec! changes. Nevertheless, the concept pro- posec! by Haurwitz of latituclinal clifferential heating of the ozone layer cluring times of high solar activity, as has been postulates! over solar-rotation or solar-cycle periods, contin- ues to be one of the main directions of stucly in the search for solar-weather relations. Difficulties hac! been cleveloping in his marriage, en c! in early 1946 Bernharc! en c! Eva were clivorcecI. Shortly after- warc! he acceptec! an invitation from Herbert Rich! to visit the Institute of Tropical Meteorology in Puerto Rico, which at that time was aciministerec! by the University of Chicago. The visit was planner! for midsummer en c! early fall but was somewhat clelayoc! until shortly before he receiver! his natu- ralization papers. When he finally arriver! in October, Haurwitz was able to take advantage of the results of a special program of three hourly racliosoncle observations over the Eastern Caribbean to carry through a preliminary analysis of the cliurnal en c! semicliurnal pressure en c! tem- perature oscillations at various levels in the troposphere. Determination of the characteristics of solar and lunar tidal oscillations in the oceans, at the earth's surface, en c! in the free air up to heights of 100 km continued to occupy him through the rest of his research career. The following summer (1947), while he was a research associate at the Woocis Hole Oceanographic Institution
00 B I O G RA P H I C A L EMOIRS (WHOI), Haurwitz was asker! by Athelstan SpiThaus, then heat! of the Meteorology Department at New York Univer- sity, to be the new chair of the department. Haurwitz ac- ceptec! en c! in September 1947 mover! to New York as pro- fessor en c! chair of the Department of Meteorology at NYU, where he built a strong en c! interactive department. He broaclenec! its academic scope en c! soon changer! its name to the Department of Meteorology en c! Oceanography. He also arranger! to increase the size of the faculty to accom- mociate the growing number of graduate students in the department. He brought to the department an informal en c! collegial mocle, particularly among graduate students en c! academic staff, that was characteristic of his own inter- personal en c! professional style. While at NYU, Bernharc! actively worker! with other pro- fessional groups on problems of mutual interest. For in- stance, he clevelopec! a program of occasional joint semi- nars with the graduate mathematics department at NYU, which was then clirectec! by Richarc! Courant, from whom he hac! taken a course when he was a student at the Univer- sity of Gottingen. Participants in those seminars included faculty en c! graduate students of both the Department of Meteorology en c! Oceanography en c! the Courant Institute. The seminars gave both groups a chance to interact on applier! mathematical problems of atmospheric interest, such as atmospheric ticles en c! the stability of atmospheric waves. Bernharc! spent at least part of each summer (1947-55) as a research associate at WHOI, where he worker! closely with many institution colleagues, namely, Andrew Bunker en c! Henry Stommel, en c! visiting associates, namely, Rich- ard Craig, Hans Panofsky, and others. Although he couldn't swim, he clic! enjoy spencling time on the beach near Falmouth relaxing with his son, Frank. They both enjoyed New Eng- land seafood and frequently walked on the beach hunting
B E R N H A R D H A U RW I T Z 101 crabs. They both enjoyocI, en c! often attenclecI, the summer Gilbert en c! Sullivan operetta program in the area. Being at Woocis Hole also gave Haurwitz the chance to be away from New York City cluring the summer months. During his time at Woocis Hole, Bernharcl's research ef- forts were largely clevotec! to investigations of internal waves in the oceans en c! analysis of the observations en c! theoreti- cal basis for the existence of ticial oscillations, particularly of the semicliurnal lunar period, associates! with these waves. In 1950 he was able to show that, if the earth's rotation was incluclec! in the theoretical analysis, the periods of long internal waves wouIc! be reclucec! en c! their speecis increasec! so that internal waves in the oceans conic! contain motions that were characteristic of ticial oscillations. After careful statistical analysis of temperature en c! density ciata taken from ship observations at different depths en c! from re- mote recording thermometers, it was fount! that such peri- oclic oscillations may incleec! exist. But the ciata were rather noisy. In discussions about twenty-five years later of ticial influences within the oceans, Bernharc! agrees! that there was still a lack of substantial observational evidence of a lunar period at levels below the ocean surface. Bernharc! returnee! to the study of ticial oscillations in the atmosphere in the early ~ 950s. At that time he was interested in further clevelopment of resonance theory as an acloquate explanation of the solar semicliurnal pressure oscillation and to document the global distribution of the amplitucle en c! phase of these ticles. These studies contin- ucc! as a major part of his research activities cluring the remaining part of his active professional career at NYU en c! subsequently when he mover! to Coloraclo. During these times he worker! closely with a number of colleagues, namely, Sydney Chapman, Walter Kertz, Fritz Moller, Manfred Siebert, Gloria Sepuivecia, en c! Ann Cowley (one-thirc! of his papers
02 B I O G RA P H I C A L EMOIRS on atmospheric ticles were coauthored! with Ann Cowley). The areas coverer! in his ticial studies involves! analyses of (a) the cliurnal en c! semicliurnal surface-pressure oscilIa- tion, (b) the lunar semicliurnal surface-pressure oscillation, en c! (c) the cliurnal en c! semicliurnal wine! oscillation in the mesosphere. In 1956 Haurwitz publisher! an analysis of the mean an- nual glob al distribution of the solar semicliurn al surface- pressure oscillation, S2(pO). This was an extension en c! sys- tematic improvement of the representation presented by George Simpson about forty years earlier baser! on a lim- itec! ciata set. His principal motivation for the stucly was to provicle improve c! empirically derive c! cle scriptions of th e two components of the S2(po) oscillation: (a) the east-to- west-traveling wave en c! (b) the stationary zonal wave. He analyze c! the geographic distribution of the mean an- nual observer! amplitucle en c! phase of S2(pO) en c! computer! spherical harmonic representations of the improver! set of observer! values. The computer! maximum amplitucle at the equator (~.2 nib) clecreasec! to near zero at polar latitucles. The computer! local phase was approximately 9.7 hours up to about +50° but varier! locally at higher latitucles, where the stationary wave was dominant. The results of this im- portant paper were clocumentec! the following year in two studies with Gloria Sepuivecia in which they verifier! that in the Northern Hemisphere poleward of about 70° the am- plitucle en c! phase of the semicliurnal pressure oscillations are mainly controller! by the stancling wave. In the winter semester of 1955-56 Bernharc! spent a sab- batical leave visiting with Fritz Moller in Mainz, Germany, motivated, in part, by the wish to continue an earlier stucly clone with Moller at NYU on the analysis of the global clis- tributions of the semidiurnal temperature variation ASK ~ To) ~ en c! its effect on the semicliurnal pressure variation tS2(pO)~.
B E R N H A R D H A U RW I T Z 103 During that time, he hac! the chance to revisit Gottingen en c! meet with two of Bartels's students, Manfrec! Siebert en c! Walter Kertz, who were then working on the problem of direct thermal input as an alternative to resonance theory for the main forcing of the semicliurnal atmospheric ticial oscillation. MIGRATION TO THE WEST Bernharc! hac! his first onsite experiences with the Rocky Mountain region in 1954 when he began his summer visits to the western states. He spent part of that summer at the Sacramento Peak Observatory (Sac Peak) at Sun Spot, New Mexico, at the invitation of Jack Evans, then director of the observatory. There he interactec! with solar physicists who were involves! in, among other things, studies of the effect of solar disturbances on radio propagation in the upper atmosphere. Discussions with colleagues at Sac Peak brought to mine! his earlier attempts at fincling a possible physical mechanism for solar influences on atmospheric variability. The graclual shift of his summer workplace locale from WHOI on the east coast to Sac Peak in New Mexico en c! later to the High Altitucle Observatory (MAO) in Bouicler, Colo- raclo, represented! a transition towarc! increaser! research application to problems of upper-atmosphere dynamics. When Walter Orr Roberts, knowing of Bernharcl's desire to spenc! some time away from New York, asker! him to participate in the HAO summer program clearing with so- lar-terrestrial relations, Bernharc! agrees! en c! consequently spent the summers of 1957 and 1958 as a visiting research associate with the High Altitucle Observatory. In 1959 he accepted Walt's offer of a joint, full-time appointment as professor of geophysics at the University of Coloraclo en c! research associate at HAO. The attractions in Bouicler, both intellectual en c! envi
04 B I O G RA P H I C A L EMOIRS ronmental, were many. Bernharc! was able to work in more relaxer! surroundings than before, especially with a mini- mum of administrative responsibilities. After 1959, when he became a permanent resident in Bouicler, he wouic! go to the mountains almost every weekenc! hiking cluring sum- mer en c! fall en c! ski touring or snowshoeing cluring the winter and spring. Frequently he would go hiking with his son when Frank visitor! BouIcler cluring the summer or with local or visiting colleagues. One of those colleagues was Sydney Chapman, who was a member of the research staff of HAO en c! with whom Bernharc! maintainer! a close asso- ciation. They had strong overlapping scientific interests and a sharer! appreciation of Bouicler because of, among other things, its proximity to the many nearby mountain trails. One of Bernharcl's hiking companions was Marion WoocI, a scientist working at the National Bureau of Stanciarcis in BouIcler en c! a native of Coloraclo who sharer! his apprecia- tion of the mountains en c! associates! outdoor activities. Bernharc! en c! Marion were marries! in January 1961 en c! were together until his cleath twenty-five years later. Bernharc! en c! Marion went to Europe cluring the sum- mer of 1961 for an extended visit to Switzerland, Austria, en c! Germany. This was their first trip abroac! together, en c! it represented a somewhat clelayoc! honeymoon. They par- ticipatec! in scientific symposia in Arosa en c! Vienna en c! went to Munich for three months at the invitation of Fritz Moller, who was then professor of meteorology at the Me- teorological Institute in Munich. Bernhard held a professo- rial chair at the university for the summer en c! gave a course on atmospheric dynamics. During his stay in Munich, he worked principally on a representation of the global distri- bution of the ciaily variations of surface temperature through the use of Legendre functions. Some of the results of that stucly were user! in his later discussion of the possible ther
B E R N H A R D H A U RW I T Z 105 mat excitation of the observer! cliurnal surface pressure os- cilIation. After five years at the University of Coloraclo, Haurwitz cleciclec! in 1964 to move to a full-time position at N CAR as a senior scientist with the Advance c! Stucly Program, which he clirectec! for a three-year perioc! (1967-69~. He contin- ucc! his appointment at N CAR until his retirement in 1976, when he became a senior research associate. In 1964 he also starter! his affiliation with the Geophysical Institute of the University of Alaska, first as a research associate en c! then as a visiting professor. He en c! Marion went to Fairbanks for three months in what was to become an almost annual visit until the winter of 1985. Soon after he arriver! at the Geophysical Institute in Fairbanks, Bernharc! hac! the opportunity to continue to work on a problem that hac! intrigues! him since his visit with Car! Stormer in OsIo some thirty-five years before. Stormer hac! been an early en c! cliligent observer of noctilu- cent cloucis (NLC) . In ~ 930 Haurwitz was involves! in a theoretical analysis of the dynamics of billow cloucis in the lower troposphere, en c! Stormer thought that he, Haurwitz, might fins! applications of the theory to the observer! wave- forms in noctilucent cloucis. In 1961 Bernharc! publisher! a paper that attempted to draw an analogy between billow cloucis that form at an interface between two layers in the troposphere en c! billow cloucis observer! at the top of the mesosphere. As a result of preliminary analysis, however, he concluclec! that "it appears likely that the billow cloucis observer! in noctilucent cloucis are manifestations of inter- nal waves" rather than wincishear. At the Geophysical Institute, Bernharc! met Benson Fogle, who was then a graduate student working with Sydney Chapman. Fogle hac! been collecting ciata on NLC observa- tions macle in polar regions, en c! in 1966 they wrote a re
06 B I O G RA P H I C A L EMOIRS view paper describing what was then known of the observer! characteristics of these cloucis. Then in 1969, after Fogle joiner! NCAR, they publisher! a theoretical analysis of the origin of the wave forms of noctiTucent cloucis. Observa- tions indicated that the clouds generally took on two differ- ent forms: high-frequency, short-wavelength billow cloucis en c! Tower-frequency, Tonger-wavelength bancis. They pro- posec! that the shorter lifetimes for billow cloucis were prob- ably clue to viscous clamping, which is more effective for shorter than longer wavelengths. On the basis of their analysis they concluclec! that the win c! shear in the layer of the NLC bancis was certainly smaller than that requires! if these bancis appearec! as an interface wave near the mesopause, en c! they suggestec! that both bancis en c! billow cloucis are causer! by internal gravity waves. Bernharc! became convincer! that the problem of the origin en c! energy source, particularly for the high-frequency component of the NLC, conic! not be clefinitively resolver! without a carefully clesignec! obser- vational program to measure NLC heights. wavelengths. en c! amplitucles of the different waveforms. O O During this time, Bernharc! continues! with his studies of atmospheric ticles. It hac! Tong been known that the solar atmospheric surface pressure title is thermally rather than gravitationally produced. However, the observed amplitude of the cliurnal title is smaller than that of the semicliurnal tide, which is apparently inconsistent with the relative am- plitucles of the cliurnal en c! semicliurnal temperature oscil- lations. In a paper publisher! in 1965 Bernharc! pointer! out that "one of the main problems of atmospheric ticial theory is to explain the small size of So (p0) as compared to S2(pO)." It was by then generally agrees! that resonance conic! not be the major cause for the large amplifications of S2(pO). Reso- nance theory, normally acceptec! up to ten years earlier to explain the dominance of S2(po), required that the atmo
B E R N H A R D H A U RW I T Z 107 sphere have a free perioc! very close to twelve hours. This wouIc! call for an upper-stratospheric temperature of about 350 K, 75 K higher than observed. By the early 1960s, how- ever, it hac! been shown by Siebert, Butler, Small, en c! oth- ers, that direct heating by absorption of solar racliation by water vapor en c! ozone in the troposphere en c! stratosphere conic! largely account for the observer! amplitucle of S2(pO). In the 1965 paper Haurwitz presented for the first time a spherical harmonic analysis of the worIc~wicle geographic distribution of So (po), similar to that done earlier for S2(pO), to document the observer! relative amplitucles of the two principal components of the surface pressure solar title en c! to explain the apparent suppression of S~(pO). He shower! that the main part of SO (pO) was a westwarcI-traveling wave with an equatorial amplitucle of~O.6 mb, one-half that of S2(po). Also, the average amplitucle of the cliurnal oscilla- tion clecreasec! strongly with latitucle, en c! the cliurnal wave, unlike the semicliurnal wave, was strongly moclifiec! by prop- erties of the Tower boundary such as orography en c! the distribution of lane! en c! water surfaces. Bernhard, however, erroneously attributer! the excitation of SO (pO) to the ciaily surface temperature oscillation, So (To). At the time of the analysis, he clic! not realize that the representation of SO (pO) by Hough functions shouIc! contain negative equivalent depths, as later pointer! out by Richarc! Lincizen en c! oth- ers. The excitation of such Hough mocles wouIc! result from absorption of solar racliation principally from water vapor and ozone in the Tower and upper stratosphere, respec- tively. For a number of reasons, the propagation of this energy from the source regions to the surface is not very effective, thus producing a diminished SO (pO). In his last major study of atmospheric ticles (completec! in 1973), Bernhard, together with Ann Cowley, presented an analysis of the quasi-global distribution and seasonal varia
08 B I O G RA P H I C A L EMOIRS lion of the cliurnal en c! semicliurnal pressure oscillations. Again, they performec! spherical harmonic analyses of the station ciata, en c! the wave characteristics were expressed by associates! Legencire functions en c! Hough functions. They extenclec! their earlier studies to higher-orcler wave num- bers en c! confirmed! that the dominant component of the cliurnal wave was zonal wave number ~ en c! that for the semicliurnal wave was zonal wave number 2. The more com plete study again shower! that at the equator the ratio of the relative amplitucles of So (p0) to S2(pO) was approximately I:2. S2(pO) was fount! to be much more regular than Situps), a result that is consistent with the nature of the forcing of the two waves. The results of this study are cites! in the literature as one of the stanciarc! references on atmospheric ticles. While at N CAR, Bernharc! wouic! frequently give courses at Coloraclo State University en c! in 1973 he en c! Marion mover! to Fort Collins. For the next three years he cliviclec! his time among CSU, NCAR, en c! the Geophysical Institute at Fairbanks. In 1976 he resigner! his formal N CAR posi- tion but kept his ties to NCAR as a senior research associ- ate. Bernharc! was electec! to the National Academy of Sci- ences in 1960, en c! in 1964 he was electec! to the Deutsche Akaciamie cler Naturforscher Leopoiclina (the German AcacI- emy of Sciences, founclec! in 1562~. He was awarclec! the Order of Merit First Class by the Fecleral Republic of Ger- many in 1976 for his efforts in helping German meteorolo- gists return to the mainstream of the international scien- tific community in the years following WorIc! War II. Bernharc! received the prestigious Car! Gustaf-Rossby Award for Ex- traorclinary Scientific Achievement from the American Me- teorological Society in 1962, en c! in 1972 he receiver! the Bowie Mecial of the American Geophysical Union.
B E R N H A R D H A U RW I T Z 109 In December 1985 while he was in Fairbanks, Bernharc! clevelopec! a chest infection that was cliagnosec! as pneumo- nia, en c! he returnee! with Marion to Fort Collins. He was hospitaTizec! in January, en c! on February 27, 1986, he cliec! of renal failure. Bernharc! represented a prime example of a person who successfully combiner! superior teaching with excellence in research by removing the unnatural barrier that often sepa- rates the two. He was unpretentious, en c! although he clic! not suffer fools, his interchanges with students en c! col- leagues were never market! with derogation. It is clear that he left a strong imprint on his colleagues ant! students through his writings en c! lectures. Both were outstanding examples of ticliness en c! clarity with a stucliec! avoidance of jargon, particularly when dealing with complex and diffi- cult subjects. IN PREPARING THIS MEMOIR, considerable use was made of the material contained in a series of papers, "Meteorology in the 20th Century- A Participant's View," by Bernhard Haurwitz, published in 1985 in the Bulletin of the American Meteorological Society (vol. 66, pp. 281-91, 424-31, 498-504, 628-33), and Conversations with Bernhard Haurwitz, by George W. Platzman (NCAR/TN-257, 1985~. I am indebted to George Platzman for many discussions about Bernhard and for his comments on an early draft of this memoir.
0 B I O G RA P H I C A L S E L E C T E D EMOIRS B I B L I O G RAP H Y A full bibliography is contained in Conversations with Bernhard Haurwitz, by George W. Platzman, NCAR/TN-257, June 1985, National Cen- ter for Atmospheric Research, Boulder, Colo. 1927 Bezichungen zwischen Luftdruck- und Temperaturanderungen. Ein Beitrag zur Frage des Sitzes dur Luftdruckschwankungen. (Doctor's thesis. ~ Veroeff Geophys. Inst. Univ. Leitzig 3 :266-335. 1930 Zur Berechnung von oscillatorischen Luft- und Wasserstromungen. Gerlands Beitr. Geophys. 27:26-35. 1931 Zur Theorie der Wellenbewegungen in Luft und Wasser. (Habilitationsschrift.) Veroeff Geophys. Inst. Univ. Leitzig5~1~. .. Uber die Wellenlange von Luftwogen. Gerlands Beitr. Geophys. 34:213 32. 1932 .. Uber die Wellenlange von Luftwogen (2. Mitteilung). Gerlands Beitr. Geophys. 37: 16-24. 1935 On the change of the wind with elevation under the influence of viscosity in curved air currents. Gerlands Beitr. Geophys. 45:243-67. The height of tropical cyclones and of the "eye" of the storm. Mon. Weather. Rev. 63:45-49. 1937 The Physical State of the Upper Atmosphere. Toronto: Royal Astronomi- cal Society of Canada. The oscillations of the atmosphere. Gerlands Beitr. Geophys. 51:195- 233. 1940 The motion of atmospheric disturbances. 7. Marine Res. 3:35-50.
B E R N H A R D H A U RW I T Z 111 The motion of atmospheric disturbances on a spherical earth. 7. Marine Res. 3:254-67. 1941 Dynamic Meteorology. New York: McGraw-Hill. 1944 With T. M. Austin. Climatology. New York: McGraw-Hill. 1947 Internal waves in the atmosphere and convection patterns. Ann. N.Y. A cad. Sci. 48:727-48. 1948 Solar activity, the ozone layer, and the lower atmosphere. In Centen- nial Symposia, Harvard Observatory Monograph, vol.7, pp. 353-69. 1951 The motion of binary tropical cyclones. Arch. Meteorol. Geophys. Bioklimatol. A4:73-86. 1952 With R. A. Craig. Atmospheric Flow Patterns and Their Representa- tion by Spherical-Surface Harmonics. Geophysics Research Pa- per, No. 14. 1956 The geographical distribution of the solar semidiurnal pressure os- cillation. Meteorology Paper 2, No. 5. 1959 With H. Stommel and W. H. Munk. On the thermal unrest in the ocean. In The Atmosphere and the Sea in Motion, Rossby Memorial Volume, ed. B. Bolin, pp. 74-94. New York: Rockefeller Institute Press. 1961 Wave formations in noctilucent clouds. Planet. Space Sci. 5:92-98.
112 BIOGRAPHICAL MEMOIRS Frictional effects and the meridional circulation in the mesosphere. J. Geophys. Res. 66:2381-91. 1964 Tidal Phenomena in the Upper Atmosphere. Technical Note No. 58. Geneva: World Meteorological Organization. 1965 The diurnal surface-pressure oscillation. Arch. Meteorol. Geophys. Bioklimatol. A14:361-79. 1969 With B. Fogle. Wave forms in noctilucent clouds. Deep-Sea Res. 16 (Suppl.) :85-95. With A. D. Cowley. The lunar barometric tide, its global distribu- tion and annual variation. Pure Appl. Geophys. 77: 122-50. 1973 With A. D. Cowley. The diurnal and semidiurnal barometric oscilla- tions, global distribution and annual variation. Pure Appl. Geophys. 102:193-222.
