Otto Jesse and the Investigation of Noctilucent Clouds 115 Years

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Otto Jesse and the Investigation KpMdfr of Noctilucent Clouds 115 Years Ago Wilfried Schroder Bremen-Roennebeck, Germany

ABSTRACT

Extracts from Otto Jesse's papers relating to twilight studies, noctilucent clouds, and atmospheric movements are presented here to illustrate his contribution to the subject during the years 1884-1901. The most important result of his activity was the establishment of the Berlin Atmospheric Programme, which included regular monitoring of noctilucent clouds by visual and photographic means. Furthermore, Jesse studied problems of dynamic processes in noctilucent clouds and in the corresponding upper-atmospheric layers.

1 • Introduction Berlin). Such a discussion is rather difficult as Jesse's personal papers are not available. One hundred and fifteen years ago, as darkness For recent studies and theoretical discussion see came over Berlin, the astronomer Otto Jesse (Fig. 1) Schroder (1998) and Thomas (1991, 1994, 1996). started his observations in the twilight. Looking to- ward the northeast he found silvery bands, ripples, and waves in the cloud-form, a phenomenon he had never 2. The earliest reports on noctilucent observed before. These beautiful clouds in the evening clouds sky showed variations in brightness and in shape. That was the hour of the birth of a new discipline in upper- The first world-wide observations of anomalous atmospheric physics, and Jesse started a program to twilight phenomena from the year 1883 (Perntner investigate these clouds, which were later named noc- 1889; Peters 1893) are without doubt connected to the tilucent clouds. earlier volcanic eruption of Krakatoa in the Sunda Ertel outlined the "phases of the development of Strait. In central Europe, no observations of noctilu- geophysics" in his lecture at the Academy of Sciences cent clouds were recorded, even in 1884, as evident in Berlin. Such phases of development are also evi- from Jesse's following remark: "I observed often, in dent with regard to the study of noctilucent clouds the summer of 1884, the purple light and carried out a (Schroder 1975, 1998). greater number of measurements on it. The phenom- This paper discusses the initial phase of research enon of noctilucent clouds would not therefore have into noctilucent clouds. Research in this field is only escaped my attention if they were already visible at that possible today because of earlier contributions to the time" (Jesse 1888, p. 90). Even a thorough analysis of topic made at the Berlin Astronomical Observatory other German observations from different sources (i.e., (then part of the German Academy of Sciences in from the years before 1885) brought no definite sightings of noctilucent clouds (see Schroder 1998). Prominent noctilucent clouds were observed in central Europe beginning on 23 June 1885. Jesse Corresponding author address: Dr. Wilfried Schroder, (1886) remarked that there are many reports about the HechelstraBe 8, D-28777 Bremen-Roennebeck, Germany. E-mail: [email protected]. phenomenon on 23 June. He added that he observed In final form 25 May 2001. noctilucent clouds in Berlin on 23,24, and 30 June and ©2001 American Meteorological Society on 1, 2, 6, 7, 8, 17, 19, 21, and 22 July. Jesse (1886)

Bulletin of the American Meteorological Society 2421

Unauthenticated | Downloaded 09/24/21 07:59 AM UTC within the cloud structure were extremely rapid, so that they could only be observed for some minutes at a certain point" (Jesse 1886, p. 18). In 1885, Jesse planned a program of observation of the noctilucent clouds and presented it in 1887. He emphasized the necessity of cooperation between observers as a precondition for the continuous monitoring of noctilucent clouds. He wrote: "The possibility of such observations seems to be extremely rare; up to now I could not ascertain whether such phenomena had been previously observed. This makes the widest participation in the observations even more desirable" (Jesse 1887, p. 179). Finally Jesse proposed the following main objectives for the observational program:

1) Determination of the movement and velocity of complex cloud displays and different forms (waves, bands, surfaces). 2) Determination of the height of noctilucent clouds by triangulation with photographic data from different stations in Berlin-Steglitz, Nauen, Potsdam, and partly from Warnemiinde (all in Germany). 3) Photometric measurements and spectroscopic investigation of the clouds and atmospheric level and twilight. This includes estimation of intensity of FIG. 1. Otto Jesse (1838-1901). light at different heights and different observation times, measurements of spectroscopic matter of published two comprehensive reports on these obser- light, and polariscopic measurements of the light vations. V. K. Tseraskii (1849-1925) in Russia was during the events. Furthermore the sky should be also involved in upper-atmospheric research and be- observed during days (polariscopic and photomet- ginning in the 1880s he studied noctilucent clouds. He ric) on which the clouds might be visible. Those also organized some height determinations (cf. investigations may be helpful in detecting the ex- Bronsten and Grisin 1970; Schroder 1975). There may istence of clouds during the daytime. be correspondence between Jesse and Tseraskii but no 4) Most of the observations can be started from one letters have been found despite careful research station, but in general a more widespread observa- through the years by several authors. On the other tion system should be installed. hand, it is of interest that Jesse was in contact with the Krakatoa Committee of the Royal Society (in the He wrote further in a manual for the observations: same way as the German physicist Johann KieBling "Although it is desirable that observations should be who published two books on the Krakatoa event). carried out according to this programme, nevertheless Immediately after the appearance of noctilucent it would be—especially concerning the periodic ap- clouds, Jesse asked different scientific institutions to pearance of the phenomenon—sufficient if reports inform him "if this phenomenon was only local or had become available from non-European stations about greater extent" (Jesse 1886, p. 8). The responses indi- the times when the phenomenon appeared" (Jesse cated that noctilucent clouds had been observed at 1887, p. 180). With regard to the collection of non- many places in Europe. Furthermore, Jesse gave a European observations, it is to be remarked that the description of the phenomenon: "The form of the then Marine Observatory in Hamburg, Germany, pub- clouds was very similar to cirrus clouds. Often only lished an "invitation to mariners, especially to those singular wisps were observed; more often they re- in middle and higher southern latitudes" (Jesse 1888, sembled compact cirrostratus clouds. The changes p. 93) initiated by Jesse. Concerning the monitoring

2382 Vol. 82,, No. 7 7, November 2001 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC of noctilucent clouds as the main aim of Jesse's project, Steglitz, Nauen and Rathenow in a programme led by the following sentence is quoted from Archenhold O. Jesse. The photographs were taken in Steglitz by (1894, p. 4): "Due to the indeterminable irregular appear- Jesse, in Rathenow by Hoeffler and in Nauen by ance of noctilucent clouds, this observational programme watchmaker Mr. Baeker, the son of the deceased is one of the most arduous in the astronomical field. Nauen watchmaker Baeker who was known as the dis- It means that, during each summer night, without ex- coverer of several comets. The distance between ception, one has to remain awake at the post from 9 Steglitz and Nauen is 35 km, that between Steglitz and p.m. till 3 a.m. and to search the night sky for these Rathenow 70 km, this being adequate for the deter- formations from Northeast to Southwest." mination of the position of these clouds" (Foerster The systematic photographic monitoring of noc- 1890, p. 102). Photographic monitoring was contin- tilucent clouds was started in 1887. Jesse (1889, ued in 1890, too. Foerster (1891, 88-89) wrote about p. 269) wrote: "On the inspiration of Professor it as follows: "Mr. O. Jesse from our staff and his Foerster in Berlin, Dr. Stolze in Berlin and myself in colleagues mentioned in the previous report, together Potsdam we simultaneously took photographs of noc- with the astronomer. Archenhold and Mr. Heuer took tilucent clouds on the evening of July 6, 1887 . . ." many photographs of noctilucent clouds during spring (cf. Figs. 2 and 3). After 1887, continuous observa- and summer 1890 in Steglitz, Nauen and Rathenow tions of noctilucent clouds were carried out in the as well as from the Astronomical Observatory of the Berlin Astronomical Observa- tory. Foerster (1832-1921) commented: "In these years the Berlin Astronomical Observa- tory succeeded in taking simultaneous photographs of this cloud phenomenon at three to four stations, so that not only the position and height of these clouds could be determined, but their movements, too, by com- paring and measuring the pictures on the photographic plates" (Foerster 1906, p. 46). Around the same time, Foerster published five photographs of noctilucent clouds. Jesse's results were published in the Annual Reports of the Berlin Astronomical Ob- servatory, where he worked. Foerster reported for the year 1889: "The Berlin Astronomical Observatory has participated fi- nancially and by the contributions of their staff, Mr. O. Jesse and astronomer Hoeffler, who introduced into astronomy at the Observatory, the photography of noctilucent clouds. These photographs were taken between the end of May and the beginning of August 1889 at three stations in the vicinity of Berlin, namely FIG. 2. One of the first original noctilucent cloud photographs by Jesse (2 Jul 1889).

Bulletin of the American Meteorological Society 2421 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC it was impossible to establish a chain of at least two stations where corresponding photographic imaging could be carried out." The situation seemed to be better for the photographic study of the noctilucent clouds in 1894, as Foerster (1894) mentioned in his report that some work of this nature was done. The last studies of noctilucent clouds were carried out at the Grunewald station of the Berlin Astronomi- cal Observatory and the project was abandoned in 1896. Jesse left the observatory in 1896 and joined the Astronomical Computation Institute headed by J. Bauschinger (1860-1934). He published, however, in 1896 one of his most significant papers on the exact height determination of noctilucent clouds in which he made use of the photographs from Steglitz, the Astronomical Observatory Urania in Berlin, Nauen, and Rathenow taken on the nights of 22 June and 2, 24, and 31 July 1889; 6, 10, and 24 July 1890; and 25 June 1891. The discussion of possible error sources in the data series included a most important remark from Jesse concerning the morphology of noctilucent clouds: "It is supposed that in addition to the mentioned two sources of errors a third is also present and apparently this derives from the difference of the accumulation of particles constituting the noctilucent FIG. 3. Otto Jesse's noctilucent cloud observatory. clouds. It is further not unlikely that the vertical ex- tension of the layer of the noctilucent clouds is dif- Urania Society. These not only confirm previous re- ferent at different times" (Jesse 1896, p. 166). sults published by Jesse in the summer of 1890 in the Concerning the height determination, Jesse (1896, Reports of the Academy of Sciences, but also yield p. 168) concluded: "The statement is valid, in spite of new results concerning the direction and velocity of this not very significant uncertainty, that noctilucent the movement of these clouds." clouds appeared in the years 1889-1891 at heights al- The photographs and observations made in the ways close to the same value, namely 82 km." years 1889-90 were discussed in detail by Jesse in a Photographs of noctilucent clouds from the year publication presented by W. von Betzold (a meteorolo- 1894 were later evaluated by Archenhold (1928). gist) at the Berlin Academy of Sciences. This publi- Jesse's last work, published during his lifetime, dealt cation was the first comprehensive report on the study with the height of noctilucent clouds. The Annual of noctilucent clouds. The photographs taken in 1890 Report of the Computation Institute, published by were published by Archenhold (1894); in the years Bauschinger, showed that Jesse completed a paper in 1891-92, Jesse and his group carried out further pho- 1897 with the title "The noctilucent clouds and the tographic studies in Berlin. Foerster (1894, p. 101) resistant material of general space," which he pre- wrote about the year 1893 in the Annual Report of the sented to the Berlin Academy for publication. This Astronomical Observatory: "Concerning the continu- paper was, however, not published among the papers ation of the photographic study of noctilucent clouds, of the academy, although Archenhold (1928) referred Mr. F. S. Archenhold devoted his attention in 1893 to to it later in detail. the completely equipped observing station of the As- Jesse was interested in noctilucent clouds even af- tronomical Observatory in Grunewald, where he suc- ter leaving the Berlin Astronomical Observatory. ceeded in seeing undoubted noctilucent clouds on Bauschinger stated in the Annual Report of the Ob- some nights. The circumstances there were, however, servatory of 1898 that Jesse had founded a cloud sta- disadvantageous for photographic studies; moreover tion (Fig. 3). Archenhold also referred to this cloud

2382 Vol. 82,, No. 7 7, November 2001 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC station in Jesse's obituary: "On the 3rd April this year, on these photographs, which led to the conclusion that a small group of mourners gathered to escort his ashes in this height range (80-85 km) wind fields have ex- from the house, from the roof of which he had ob- tremely rapid variations. Archenhold (1894) wrote on served noctilucent clouds for many years. On the way the observed changes in a noctilucent cloud: "The to the cemetery, with grief we passed the Cloud Sta- noctilucent cloud is, in its initial state, subject not only tion which was established by friends for Otto Jesse, to very quick changes—new branches of the cloud but which he had hardly used due to his illness" (Foerster 1901).

3. Jesse's results

Otto Jesse carried out and organized systematic observations of noctilucent clouds in the period 1885-99 and this fact alone would be sufficient to ensure him a place in the history of science (Bronsten andGrisin 1970; Vasilyev 1967). Furthermore, his later special studies also led to results that are most significant for current research (Schroder 1975, 1998). It was undoubtedly a pioneering achievement that Jesse succeeded in organizing the photographic monitoring of noctilucent clouds. From this he established the height of these clouds and found an average value of 82.08 km (Table 1), this value being confirmed by recent investigations (Bronsten and Grisin 1970). This was the first proof of the existence of clouds at this height in the terrestrial atmosphere. This result was de- scribed by Foerster (1906, p. 53) as follows: "Based on such photographs taken in the years 1888-1891 it was established that Jesse's clouds occurred with very high probability over the northern Baltic Sea and southern Sweden, at a range of 100 to 700 km from us and that FIG. 4. Original letter by Jesse. In this letter Jesse discussed the possible review of they drifted above the Earth's KieBling's book The Twilight Phenomena. KieBling had studied in detail the twilight il- surface at a height always close lumination after the Krakatoa event and summarized the data and offered some physical explanations. As Jesse pointed out, the review was done and the editor added a note in to 82 km." Jesse could also dem- Jesse's paper on noctilucent clouds (Jesse 1889). The editor should have informed Jesse onstrate chaotic changes within if a further review was requested. This handwritten letter of Jesse is a rare document, single noctilucent clouds based because most of his papers and scientific journals had been destroyed after his death.

Bulletin of the American Meteorological Society 2421 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC TABLE 1. Height measurements of noctilucent clouds from the photographic method by Jesse.

No. Weigh of Avg height of the points of (Validity Place Time (LT) and date points noctilucent clouds (km) of measurements)

St, N 1353 22 Jun 1889 14 82.94 ±0.116 74,3 82.58 ±0.118 72,0 St, N 1321 2 Jul 1889 10 82.78 ± 0.179 31,3 82.62 ±0.211 22,4 St, N 1339 2 Jul 1889 21 80.75 ±0.100 99,6 81.17 ±0.090 123,5 St, N 1344 2 Jul 1889 32 82.78 ± 0.039 671,1 83.07 ± 0.039 671,1 St, N 1406 2 Jul 1889 14 81.52 ±0.147 46,1 81.92 ±0.168 35,2 St, N 1447 24 Jul 1889 10 85.51 ±0.054 341,7 86.56 ± 0.062 259,3 St, N 1448 31 Jul 1889 15 88.53 ± 0.308 10,5 87.40 ± 0.292 11,7 St, R 1311 6 Jul 1890 3 84.32 ± 0.640 2,4 83.35 ± 0.693 2,1 St, R 1322 6 Jul 1890 2 82.17 ±0.117 73,3 81.44 ±0.218 20,9 St, R 1327 6 Jul 1890 3 86.03 ± 0.525 3,6 83.89 ± 0.558 3,2 St, R 1341 6 Jul 1890 3 83.99 ±0.311 10,4 83.46 ± 0.365 7,5 St, R 1346 6 Jul 1890 2 83.12 ±0.048 439,5 82.57 ± 0.058 293,2 St, R 1034 10 Jul 1890 15 83.06 ±0.120 69,7 83.22 ±0.144 48,1 N, R 1034 10 Jul 1890 13 83.49 ± 0.222 20,3 83.82 ± 0.255 15,4 N, R 1053 10 Jul 1890 10 87.30 ± 0.250 16,0 86.62 ± 0.294 11,6 St, R 1336 10 Jul 1890 9 83.06 ±0.124 64,8 82.11 ±0.114 77,3 St, R 1349 10 Jul 1890 23 81.19 ± 0.036 771,7 80.27 ± 0.038 696,3 Ur, R 1410 10 Jul 1890 16 82.54 ± 0.068 218,0 81.23 ±0.072 195,6 St, R 1422 24 Jul 1890 3 82.95 ± 0.057 304,50 82.90 ± 0.069 208,2 St, N 1324 25 Jun 1891 15 83.22 ±0.106 89,2 83.60 ±0.106 89,9 St, N 1329 25 Jun 1891 18 82.60 ± 0.066 229,6 82.88 ± 0.066 228,2 St, N 1329 25 Jun 1891 17 81.44 ±0.133 56,7 81.54 ±0.132 57,2 St, N 1350 25 Jun 1891 8 81.21 ±0.018 2985,0 81.73 ± 0.020 2403, St, N 1410 25 Jun 1891 11 81.70 ±0.092 149,1 82.04 ± 0.082 148,0

St = Steglitz, N = Nauen, R = Rathenow, Ur = Berlin (Urania). The average height of noctilucent clouds has been determined to be 82.08 km ± 0.009.

2382 Vol. 82,, No. 7 7, November 2001

Unauthenticated | Downloaded 09/24/21 07:59 AM UTC emerge then disappear again in a few minutes—but positive records were made. At that time people ob- also to strong changes in light intensity. Some pho- served the events and speculated on their nature. A re- tographs of the noctilucent clouds made in quick suc- lation to the Krakatoa event was possible. In 1890 and cession in the year 1890 very clearly show these form following years, Jesse discussed his data more in de- and light changes." Finally Jesse also established the tail, and he suggested that between the increased twi- annual changes of the frequency of occurrence of noc- light after 1883 and Krakatoa a close relation existed. tilucent clouds. Foerster remarked: "The clouds were Furthermore, he suggested that the origins of noctilu- observed in Berlin in the interval between the end of cent clouds can be caused by small crystals, which are May and the end of July" (Foerster 1906, p. 53). formed by the low temperature of the upper-atmo- As an early stage in his work, Jesse considered the spheric level. This point is an interesting insight by origin of noctilucent clouds and their essential features Jesse, who pointed out early on the relation between (Jesse 1888). He discussed in this paper and in his formation of clouds and possible lower temperature, study "Noctilucent clouds and their resistant material considering he did not have exact data! The origin of in general space" the connection between noctilucent the particles was suggested in the material that was dis- clouds and the existence of a so-called resistant mate- tributed into the upper atmosphere after the Krakatoa rial. Archenhold (1928, p. 141) remarked about this event. The formation of a layer that produced the fine hypothesis: "Jesse supposed that both seasonal crystals that were necessary for genesis of noctilucent changes in the frequency of occurrence of noctilucent clouds needs some time. This explains the time be- clouds and their movement could be easily explained tween the Krakatoa event (1883) and the first sight- if we suppose the existence of a resistant material in ing of clouds in 1885. In the years after 1889 Jesse our solar system." The notion of a resistant material found that noctilucent clouds appeared less frequently. is also discussed by Foerster (1906, 1911) in connec- He explained this decrease by the effect that follow- tion with noctilucent clouds. Some further considering by the downward of particles. Only a few particles ation of the origin of noctilucent clouds was published exist than in the upper atmosphere which are avail- by Archenhold (1894, p. 6): "In order to explain the able for the formation of clouds. It is also of interest sudden changes of the structures and visibility of noc- that Jesse suggested an atmospheric circulation for the tilucent clouds, I propose that noctilucent clouds are upper atmosphere: during January to June a very slow due, not only to reflections of the Sun's light, but to current from the south to the north, in the following an optical phenomenon similar to that in vacuum tubes half year the same procedure from north to south. (Geisslerian tubes) due to electroluminescence". From this, he explained the seasonal frequency of But in general Jesse found from his measurements clouds and their observed maximum in July of the that noctilucent clouds are the highest "clouds" that Northern Hemisphere. This is an interesting explana- appear in earth's atmosphere. Furthermore, it became tion because scientists at the end of nineteenth cen- clear to him that they were not connected to the tury had no data of the real atmospheric temperature weather or any tropospheric disturbances. There was or circulation at the 80-km level. From this, supported no relation between the typical "weather clouds" and by the later investigations of Foerster, at the end of noctilucent clouds. The fundamental result of Jesse's the nineteenth century, scientists explained noctilucent research was the discovery of the nearly constant clouds as being of volcanic origin, partly built upon height of noctilucent clouds, their movement, and small crystals in the upper atmosphere and possible brightness fluctuation. Another interesting result was local conditions. An interesting point was that Jesse the seasonal variation in their appearance, which concluded from his hypothetical work that only fur- showed that they are typical "summer clouds" in the ther and complex studies from the Northern and Northern Hemisphere. Due to limited knowledge of Southern Hemispheres could help one understand noc- the corresponding physics (there are no data on tem- tilucent clouds better. From a modern viewpoint, these perature, composition, or circulation of 80-km height studies of Jesse and later Foerster are of interest. They available for Jesse's research), he could not present a both pointed out that noctilucent clouds appeared at generally valid theory of noctilucent clouds (cf. very high altitudes, and that the earth's atmosphere Schroder 1975, 1998). For more recent studies in this reaches into the cosmos (similar finding have been subject see the papers by Thomas (1991, 1994,1996). made by the first high determinations of auroras by Noctilucent clouds were observed after the volca- Galle and Jesse; see Schroder 1975, 1998). This re- nic event of Krakatoa, in August 1883. In 1885 the first sult gives a new understanding of the earth's atmo-

Bulletin of the American Meteorological Society 2421 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC and the global explanation gave TABLE 2. Progress in noctilucent cloud research. A list of references is provided in new insight and stimulated fur- Schroder (1998). NLC is noctilucent clouds. ther research. Shortly after Jesse, several Norwegian re- Year Topic Researchers searchers used the cameras em- ployed by Jesse for triangulation 1855 ff Climatological studies Jesse of the aurora, and Birkeland and 1890 NLC as manifestations of Krakatoa Jesse, Foerster later Stormer showed the exist- injection ence of the aurora in high levels of the atmosphere. Modern at- 1910 ff NLC as ice crystals Wegener mosphere physics had grown up (similar to cirrus clouds) by the end of the nineteenth century. 1926 NLC and meteoric dust Jandretzky, Maizev In the following decades, after Jesse's death, research was 1935 NLC and cosmical influence (meteors) Stormer, Hoffmeister dependent on observer's atten- 1955 NLC and micrometeorite influence; Hoffmeister tion and only a few new insights cosmical dust particles; Astapovic, Fessenkov were published. Most data were climatological research Paton, Fogle, Schroder, regular observations by astrono- Villmann, Vasilyev mers from Germany and Russia. A new decade for research 1962 NLC and low temperature (from rocket Theon, Smith, Nordberg, started with the International data) Witt, Khvostikov et al. Geophysical Year (1957-58), in 1968 NLC and transition periods of Schroder which noctilucent clouds were a 1970 ff mesosphere central part of the observations. But also at that time little infor- 1969 ff NLC and ion components Witt, Khvostikov et al. mation on the constitution of the mesosphere was available and 1985 ff Polar mesospheric clouds (PMC), NLC Thomas, Olivero, von most hypotheses were those of Zahn "cosmic origin," where meteor-

1989 Secular variation of NLC Thomas et al. itic substances play an active role in the formation of clouds. 1990 ff PMC echoes/PMC/NLC Thomas, von Zahn, A new era started with the first Liibken et al. direct rocket measurements in the beginning of the 1960s. These first direct data showed sphere, which was larger than most scientists had been that noctilucent clouds were correlated with very low suggesting at that time. The connection between the temperatures in the mesopause region. It seems to be Krakatoa particles, increased airglow, and formation possible that cosmical particles played an active role by noctilucent clouds made the first environmental with these low temperatures in building the clouds. studies of earth's atmosphere possible, and further- A further mechanism was found with ion data, which more the explanation of these highest clouds formed had been measured by various researchers during a new discipline: aeronomy, the physics of the upper rocket experiments. G. Witt, of Sweden, played an im- atmosphere. The "new atmosphere," which had been portant role in this research, as did the Heidelberg established by the cloud measurements, made possible group of D. Krankowsky, H. Fechtig, F. Arnold, and a "new picture" of the earth's atmosphere and its con- others. At that time the interest in noctilucent clouds nection to its upper layers (which had been suggested grew and there was much speculation on their nature at that time, but had not been observed or measured). published, but no explanation was given in general. In this connection Jesse was a pioneer in the ra- Further steps in noctilucent cloud research came from tional explanation of the physical processes in the Thomas (1996), with the discovery of polar mesos- earth's atmosphere and environment. The global watch pheric clouds (J. Olivero, G. Thomas, et al.), and later

2382 Vol. 82,, No. 7 7, November 2001 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC rector. Foerster was interested in all aspects of astronomy and geophysics. He mostly participated in the organization of the German observations of twilight after the great Krakatoa event in August 1883. He supported Jesse's work in investigating the twilight phenomena and measurements of polarization. Since 1885 they regularly observed noctilucent clouds. Jesse worked mostly on noctilucent clouds, auroras, and twilight. After a short illness he died on 1 April 1901. Jesse joined the Berlin Astronomical Observatory in 1874, and in 1896 he moved to the Astronomical Computation Institute (both belong today to the Ger- man Academy of Sciences in Berlin). He retired on 1 July 1899 due to illness. His research was strongly supported by Foerster, the director of the Berlin As- tronomical Observatory at the time, who appointed astronomers F. S. Archenhold, K. Heuer, and J. F. Hoeffler to operate the photographic program and FIG. 5. Wilhelm Foerster (1832-1921). who—partly in collaboration with Jesse—published several papers on noctilucent clouds (Jesse and Foerster 1892; Jesse et al. 1894). polar mesospheric echos, which were observed and Foremost among his Berlin colleagues, was measured by many groups and which stimulated inter- Archenhold (2 Oct 1861-14 Oct 1939; Fig. 6). The national research work [studies by the Klihlungsborn Annual Reports of the Berlin Astronomical Observa- group (U. von Zahn et al.), the Bonn group (F.-J. Liibken), and many other scientists]. But in general, all these different data and many measurements could not explain the phenomena "noctilucent clouds" in general. Today we know much about the mesopause, mesosphere, and the climatology and dynamics of noctilucent clouds, but a general theory of this atmospheric phenomena is still not available. Jesse was in this development of research a singular scientist. He started a general program, and he suggested at first the connection of clouds and atmospheric content. He gave insight into climatological change (seasonal and daily frequency) and presented height measurements that are now also accepted. This pioneering work has been accepted in the scientific community, and he was a pioneer in the physics of the upper atmosphere (cf. Table 2).

4. Jesse's colleagues

Otto Jesse was born on 25 march 1838 in Breetz (Germany). After visiting the public school he started his career in earth's measurement and later became a member of the Observatory of Berlin where Wilhelm FIG. 6. Friedrich Simon Archenhold (1869-1939), coworker Foerster (16 Dec 1832-15 Jun 1922; Fig. 5) was di- of Jesse.

Bulletin of the American Meteorological Society 2421 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC FIG. 7. Modern photograph of noctilucent clouds.

FIG. 8. Modern photograph of noctilucent clouds.

2382 Vol. 82,, No. 7 7, November 2001 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC tory (Foerster 1890, 1891, 1894, 1895) show that he The fact that this comprehensive program could was decisively active in the photographic program to not be carried out was due to Jesse's deteriorating monitor noctilucent clouds. Moreover, Archenhold health. On 1 July 1899 he retired from service due to (1928) wrote a comprehensive report on noctilucent ill health and afterward could not supervise the pro- clouds after Jesse's death, in which he published promi- gram. His death meant the end of the observational nent images of the phenomenon from 24 June 1910. program (Schroder 1975,1998). Figures 7 and 8 show Jesse was supported in Berlin by K. Necker, F. Stolze, modern photos of noctilucent clouds. and O. Tetens, and the watchmaker C. Baeker assisted him by carrying out the corresponding photographic work in Berlin and Nauen. Archenhold (1928) also 5. Cooperation of the Berlin Academy refers to the help given by Jesse's sister, Pauline. Finally the cooperation of the members of the So- The Annual Reports of the Berlin Astronomical ciety of Friends of Astronomy and Cosmic Physics Observatory 1889-1891 mention that Jesse's research should be mentioned. This society of lay astronomers was supported by the Berlin Academy of Sciences. was founded by Foerster, Plassmann, Reimann, and Thus, Foerster's report for the year 1889 reads as fol- Jesse in 1891 and included a working group led by lows: "The whole undertaking, including its continu- Jesse that dealt with noctilucent clouds. Jesse, ation in the following summer, is supported by the Archenhold, and Foerster published a special hand- Academy of Sciences with a considerable sum of book: Advice for Participation in the Study of the So- money" (Foerster 1890, p. 102). Called Noctilucent Clouds. This group and their The support from the Academy induced Jesse to publication of further instructions for observations publish his important contribution (Jesse 1890b) in its (Jesse and Foerster 1892) indicated a commendable Reports on Sessions. His results concerning noctilu- early effort to carry out the monitoring of noctilucent cent clouds are therefore closely coupled to the ear- clouds on a very wide basis, including interested lier Berlin Academy. friends of nature. Foerster characterized the spirit of Although the research program conceived by Jesse these amateur observers as follows: "The participa- could not be completely carried out during his lifetime, tion in such a great cosmic research programme, even his aims have recently been mostly realized. Extended in a very modest form, gives an incomparable satisfac- observational networks were organized in the former tion which is perhaps even more intense in laymen and Soviet Union (Bronsten and Grisin 1970; Vasilyev friends of the research than in experts, as in the latter 1967; Villmann 1968), in Poland (Kosibowa and Pyka the intensity and stress of the work mars the simple 1970), in England (Paton), and in North America joy and pleasure in the splendour of these thoughts." (Fogle). At Ronnebeck, Germany (Schroder), compre- Jesse proposed a program for the photographic hensive visual and photographic observations have monitoring of noctilucent clouds within the working been carried out. These studies have not only con- group of the Friends of Astronomy and Cosmic Phys- firmed many results by Jesse, but have also contrib- ics. In the foreword of these instructions he wrote: uted to a better understanding of the corresponding "The phenomenon of noctilucent clouds becomes less problems (Megrelisvili and Khvostikov 1970; Thomas frequent from year to year and less luminous, too. 1991, 1994, 1996). Therefore it will be more and more difficult to obtain simultaneous observations at several locations for the determination of their height. Such determinations are, References however, of great importance from several points of view, so that it is very important that observers should Archenhold, F. S., 1894: Die Verwendung der Photographie bei pay the greatest attention to this phenomenon when it der Erforschung der leuchtenden Nachtwolken, Sternschnuppen appears in the near future and to capture it photographi- und Nebelflecken (Photographic research on noctilucent cally as often as possible" (Jesse 1890a, p. 31). In the clouds, meteors and cosmical nebulae). Photogr. Mitt., 31, 3-6. framework of this program Jesse suggested a continu- , 1928: Die leuchtenden Nachtwolken und bisher un- ous monitoring of the night sky, as he wrote: "Even veroffentlichte Messsungen ihrer Geschwindigkeit. (Noctilu- during nights when no noctilucent clouds appear, one cent clouds velocity). Weltall, 27, 137-144. should make notes about the appearance of the night Bronsten, V. A., 1970: K istorii otkrytija i pervych issledovonij sky at different times" (Jesse 1890a, p. 13). serebrstych oblakov. Fizika Mezosfernych (Serebristych)

Bulletin of the American Meteorological Society 2421 Unauthenticated | Downloaded 09/24/21 07:59 AM UTC oblakov (On the History of Noctilucent Cloud Research), , 1888: Uber die leuchtenden (silbernen) Wolken [On the Riga, 143-152. noctulucent (silvery) clouds]. Meteor. Z, 5, 90-94. , and N. I. Grisin, 1970: Serebristye oblaka (Noctilucent , 1889: Die Leuchtenden Nachtwolken (The noctulicent clouds). Moscow, 359 pp. clouds). Himmel Erde, 1, 186-236. Fast, N. P., and N. V. Vasilev, 1970: Novye materialy o 'svetlych , 1890a: Anweisungenfiir die Photographischen Aufnahmen nocach' leta 1908 g. Fizika Mezosfernych (Serebristych) der Leuchtenden Nachtwolken (Instructions for Photographic oblakov (New Data on Tunguska Meteorite 1908), Riga, 95- Watch of Noctilucent Clouds). Sonderdr. Ver. Freunde 101. Astron. Kosmet. Phys. Berlin, Foerster, W., 1890: Jahresbericht der Berliner Sternwarte fiir das , 1890b: Untersuchungen liber die sogenannten leuchtenden Jahr 1889 (Annual report of the Berlin Observatory). Vjschr. Wolken (Investigations on the so-called noctilucent clouds). Astron. Ges., 25, 102-103. Sitzungsber. -Ber. Preufi. Akad. Wiss. Phys.-Math. Kl., 1031- , 1891: Jahresbericht der Berliner Sternwarte fiir das Jahr 1044. 1890 (Annual report of the Berlin Observatory). Vjschr. Astron. , 1896: Die Hohe der leuchtenden Nachtwolken (The height Ges., 26, 88-89. of noctilucent clouds). Astron. Nachr., 140, 161-168. , 1892: Beobachtungen der leuchtenden Wolken (Observa- , and W. Foerster, 1892: Aufforderung zur Beobachtung der tion of noctilucent clouds). Mitt. Ver. Freunde Astron. Kosmet. leuchtenden Nachtwolken (Remarks on noctilucent clouds ob- Phys., 2, 80-82. servation). Astron. Nachr., 130, 426-430. , 1894: Jahresbericht der Berliner Sternwarte fiir das Jahr , and F. S. Archenhold, 1894: Ratschlage fiir die Betheiligung 1893 (Annual report of the Berlin Observatory). Vjschr. Astron. an der Erforschung der sogenannten leuchtenden Nachtwolken Ges., 29, 101-102. (Gruppe 6) (Instruction for noctilucent clouds observation). , 1895: Jahresbericht der Berliner Sternwarte fiir das Jahr Mitt. Ver. Freunde Astron. Kosmet. Phys., 1, 4-12. 1894 (Annual report of the Berlin Observatory). Vjschr. Astron. Kosibowa, S., and I. L. Pyka, 1970: Wyniki obserwacji nad ob Ges., 30, 143-144. okami mezosferyczynmi w Polsche w 1969 roku [Observa- , 1900: Die leuchtenden Nachtwolken (Noctilucent clouds). tions of mesospheric (noctilucent) clouds]. Przegl. Geofiz., 15, Mitt. Ver. Freunde Astron. Kosmet. Phys., 10, 66-67. 357-366. , 1901: Todes-Anzeige (Memorial note). Astron. Nachr., Megrelisvili, T. G., and I. A. Khvostikov, 1970: Atomarnyj

239-240. vodorod. Kislorod i molekuly H20 v vysokich slojach , 1906: Von der Erdatmosphare zum Himmelsraum (From atmosfery i nekotorye problemy geofiziki i fiziki okolozemnogo Earth's Atmosphere to Universe). Hillger, 115 pp. prostranstva. Fizika Mezosfernych (Serebristych) Oblakov, , 1908: Mitteilung, betreffend des Erscheinens der sogenannten 9-24. leuchtenden Nachtwolken (Note on the noctulicent clouds). Pernter, J. M., 1889: Der Krakatau-Ausbruch und seine Folge- Mitt. Ver. Freunde Astron. Kosmet. Phys., 18, 62-63. Erscheinungen (4. Die optischen Erscheinungen) (The , 1911a: Lebenserinnerungen und Lebenshoffnungen (Au- krakatoa event and related optical phenomena). Meteor. Z, 6, tobiographical Sketch). Reimer-Berlin, 351 pp. 447-466. , 1911b: Zur Frage des widerstehenden Mittels (On the "re- Peters, C. F. W., 1894: J oh. Miiller's Lehrbuch der kosmischen sisted" media). Meteor. Z, 28, 332-333. Physik. Vieweg, 907 pp. Grisin, N. I., 1957a: Issledovanija serebristych oblakov (Inves- Schroder, W., 1969: Herbstwindumstellung in der Mesosphare und tigation of noctilucent clouds). Inf. Sb. (Leningrad), 2, 16- Leuchtende Nachtwolken (Wind change in autumn in the me- 20. sosphere and noctilucent clouds). Meteor Rundsch., 22, 18-19. , 1957: O strukture serebristych oblakov (On the structure of , 1975: Developmental Phases in Noctilucent Cloud Re- noctilucent clouds). Bjull. Vses. Astron.-Geod. Obs estva search. Akademie-Verlag, 64 pp. (Moskva), 16(23), 3-6. , 1998: Noctilucent Clouds. Science Edition, 332 pp. , 1957b: Instukcija dija gidrometstancij po nabljudenijam nad Thomas, G. E., 1991, Mesospheric clouds and the physics of the serebristymi oblakami (Instruction for noctilucent cloud re- mesopause region. Rev. Geophys., 29, 553-575. search). Inf. Sb. (Leningrad), 2, 41. , 1994, Recent developments in the study of mesospheric Jesse, O., 1884: Die Hohe der Dunstschicht, durch welche die clouds. Adv. Space Res., 14, 101-112. merkwurdigen Dammerungs-Erscheinungen der letzten , 1996: Global change in the mesosphere-lower thermo- Monate hervorgerufen worden sind (On the height of the dust- sphere region. Has it already arrived? J. Atmos. Terr. Phys., level which caused the irregularly twilight-events). Meteor. Z, 58, 1629-1656. 1, 127-137. Vasilyev, O. B., 1967: Astrofizi eskie issledovanija serebristych , 1885: Auffallende Abenderscheinungen am Himmel oblakov (Atrophysical investigations of noctilucent clouds). (vorlaufige Mitteilung) (Remarkable evening sky). Meteor. Z, Inf. So obs . (Moskva), 4. 2, 311-312. Villmann, C. I., 1968: Statisti eskie dannye o pojavlenii , 1886: Die auffallenden Abenderscheinungen am Himmel serebristych oblakov za period MGSS (1964-1965 gg.) (Sta- im Juni und Juli 1885 (Remarkable evening sky in June and tistical research on noctilucent clouds. Astron. Vestn. Most, July 1885). Meteor. Z, 3, 8-18, 64-71. 2, 161-169. , 1887: Die Beobachtung der leuchtenden Wolken (Obser- vations of noctilucent clouds). Meteor. Z, 4, 179-181.

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