evidence for winds in the outer atmosphere

8
Evidence for Winds in the Outer Atmosphere Author(s): Fred L. Whipple Source: Proceedings of the National Academy of Sciences of the United States of America, Vol. 40, No. 10 (Oct. 15, 1954), pp. 966-972 Published by: National Academy of Sciences Stable URL: http://www.jstor.org/stable/89356 . Accessed: 05/05/2014 12:01 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. . National Academy of Sciences is collaborating with JSTOR to digitize, preserve and extend access to Proceedings of the National Academy of Sciences of the United States of America. http://www.jstor.org This content downloaded from 194.29.185.102 on Mon, 5 May 2014 12:01:49 PM All use subject to JSTOR Terms and Conditions

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Page 1: Evidence for Winds in the Outer Atmosphere

Evidence for Winds in the Outer AtmosphereAuthor(s): Fred L. WhippleSource: Proceedings of the National Academy of Sciences of the United States of America,Vol. 40, No. 10 (Oct. 15, 1954), pp. 966-972Published by: National Academy of SciencesStable URL: http://www.jstor.org/stable/89356 .

Accessed: 05/05/2014 12:01

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

National Academy of Sciences is collaborating with JSTOR to digitize, preserve and extend access toProceedings of the National Academy of Sciences of the United States of America.

http://www.jstor.org

This content downloaded from 194.29.185.102 on Mon, 5 May 2014 12:01:49 PMAll use subject to JSTOR Terms and Conditions

Page 2: Evidence for Winds in the Outer Atmosphere

8 D. Fultz, "Experiments with Thermally Produced Lateral Mixing in a Rotating Hemispheri- Shell of Liquid," J. Meteorol., 6, 17-33, 1949. 9 "The Role of Atmospheric Disturbances in the General Circulation," Quart. J. Roy. Meteorol. 7., 77,337-354, 1951. 0 E. W. Barrett, L. R. Herndon, and H. T. Carter, "Distribution of Water Vapor in the Strato- lere," Tellus, 2, 302-311, 1950. 1 W. N. Shaw (see D. Brunt, Physical and Dynamical Meteorology [Cambridge: At the Uni- 'sity Press, 1944], p. 12). 2 Meteorology, Part I: Discussion, British Antarctic Expedition, 1910-13 (Calcutta, 1919).

EVIDENCE FOR WINDS IN THE OUTER ATMOSPHERE*

BY FRED L. WHIPPLE

HARVARD COLLEGE OBSERVATORY

In presenting evidence for winds in the outer atmosphere, I shall limit the dis- ssion to altitudes higher than those already investigated by balloon ascensions, ighly 40 km. The attainment of a thorough understanding of winds in the upper atmosphere ,olves at least the following five major operational steps: (a) the search for and

exploitation of observational techniques that may be relevant to the problem; the validation of these various techniques, as providing measures of the actual motions at the levels observed; (c) the elimination of the observational selection ;tors that may prejudice the results; (d) the compilation and correlation analysis the relevant data with respect to a number of possible variables (including [1] ison; [2] latitude; [3] longitude; [4] energy input, transfer, storage, and dis- ation, including solar terrestrial phenomena; [5] general geomagnetic and iono- leric forces; [6] solar and lunar tides and their higher modes of oscillation; and

meteorological influences of the lower atmosphere, etc.); (e) finally, correla- n and analytical coupling of the observed data with adequate theories of atmos- eric circulation, turbulence and energy input, transfer, storage, and dissipation. 3ur interest at the moment centers on the first two steps, i.e., the observational hniques and their validation. I shall discuss each method separately with pect to these two steps. Historically, winds were first observed in the upper atmosphere through the ition of the persistent trains left behind extraordinary bright meteors or fire- [Is. E. Biot,1 in 1841, recorded early Chinese observations of this phenomenon ck to 32 B.C. Although Biot was probably quite aware of the significance of . motions and had some rough estimate of their heights, E. E. Barnard2 first ;cessfully systematized the results in 1882, while C. C. Trowbridge3 produced the It comprehensive paper on the subject in 1907. Since then, S. Kahlke,4 E. O. ilbert,5 C. P. Olivier,6 and V. V. Fedinski7 have collected the data thoroughly c from them have drawn certain limited generalizations concerning the circula- n of the high atmosphere. Quite recently, W. Lillers and F. L. Whipple9 have photographed the persistent ,ins from brighter meteors and have demonstrated numerically the enormously ;h values of wind shear commonly present in the altitude range from 81 to 113

8 D. Fultz, "Experiments with Thermally Produced Lateral Mixing in a Rotating Hemispheri- Shell of Liquid," J. Meteorol., 6, 17-33, 1949. 9 "The Role of Atmospheric Disturbances in the General Circulation," Quart. J. Roy. Meteorol. 7., 77,337-354, 1951. 0 E. W. Barrett, L. R. Herndon, and H. T. Carter, "Distribution of Water Vapor in the Strato- lere," Tellus, 2, 302-311, 1950. 1 W. N. Shaw (see D. Brunt, Physical and Dynamical Meteorology [Cambridge: At the Uni- 'sity Press, 1944], p. 12). 2 Meteorology, Part I: Discussion, British Antarctic Expedition, 1910-13 (Calcutta, 1919).

EVIDENCE FOR WINDS IN THE OUTER ATMOSPHERE*

BY FRED L. WHIPPLE

HARVARD COLLEGE OBSERVATORY

In presenting evidence for winds in the outer atmosphere, I shall limit the dis- ssion to altitudes higher than those already investigated by balloon ascensions, ighly 40 km. The attainment of a thorough understanding of winds in the upper atmosphere ,olves at least the following five major operational steps: (a) the search for and

exploitation of observational techniques that may be relevant to the problem; the validation of these various techniques, as providing measures of the actual motions at the levels observed; (c) the elimination of the observational selection ;tors that may prejudice the results; (d) the compilation and correlation analysis the relevant data with respect to a number of possible variables (including [1] ison; [2] latitude; [3] longitude; [4] energy input, transfer, storage, and dis- ation, including solar terrestrial phenomena; [5] general geomagnetic and iono- leric forces; [6] solar and lunar tides and their higher modes of oscillation; and

meteorological influences of the lower atmosphere, etc.); (e) finally, correla- n and analytical coupling of the observed data with adequate theories of atmos- eric circulation, turbulence and energy input, transfer, storage, and dissipation. 3ur interest at the moment centers on the first two steps, i.e., the observational hniques and their validation. I shall discuss each method separately with pect to these two steps. Historically, winds were first observed in the upper atmosphere through the ition of the persistent trains left behind extraordinary bright meteors or fire- [Is. E. Biot,1 in 1841, recorded early Chinese observations of this phenomenon ck to 32 B.C. Although Biot was probably quite aware of the significance of . motions and had some rough estimate of their heights, E. E. Barnard2 first ;cessfully systematized the results in 1882, while C. C. Trowbridge3 produced the It comprehensive paper on the subject in 1907. Since then, S. Kahlke,4 E. O. ilbert,5 C. P. Olivier,6 and V. V. Fedinski7 have collected the data thoroughly c from them have drawn certain limited generalizations concerning the circula- n of the high atmosphere. Quite recently, W. Lillers and F. L. Whipple9 have photographed the persistent ,ins from brighter meteors and have demonstrated numerically the enormously ;h values of wind shear commonly present in the altitude range from 81 to 113

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Page 3: Evidence for Winds in the Outer Atmosphere

i. above the earth's surface. In one installce this shear reached the value of sec., or a wind change of some 150 km/hr in 0.5 km. of altitude.

Fhe persistent trains occasionally indicate winds exceeding 100 m/sec, or 300 km/ but average values are of the order of 50 m/sec, centered about an altitude

ir 90 km. (See Figs. 1 and 2.) By the use of electronic techniques involving the measurement of Doppler- fted echoes from the ionization left behind ordinary meteors, L. A. Manning, G. Villard, and A. M. Peterson,10 of Stanford University, and also J. S. Green- w,1 of Manchester, England, have developed techniques for measuring wind ocities and directions in the meteor region. The results are in good agreement ;h the visual and photographic techniques of measurement from trains. All ;thods agree that the wind system is highly stratified and highly variable. Layers ighly a scale height apart vertically, 5-10 km., tend to differ markedly in ve- ity. Phe radio techniques in the hands of the Stanford group give, for the first time, ne indication of the vertical wind components, which do not exceed some 10 sec and are probably considerably smaller. The motion of a persistent meteor train or a meteor ion column can be shown :oretically9 to be a close approximation to the true air motion. Nevertheless, all errors are certainly introduced by the meteoric phenomenon itself. Spurious eral components arising from spraying of material must be small, but the in- ning meteoroid introduces some longitudinal motion along the trail, while heat- ; effects produce a small amount of convection. Nevertheless, it seems rather tain that we can use the motions of persistent meteor trains and meteor ioniza- n as a fairly reliable standard for calibrating other techniques. The radio- 'teor techniques have great potential value for synoptic studies, with the enor- ,us advantage of daytime operation. The altitude range, however, is firmly ablished by the physical phenomena and can rarely be utilized outside the range m 81 to 113 km. at right, but much lower in the daytime. 'he observations of noctilucent clouds, particularly by 0. Jesse,"l C. Stormer,13

I E. H. Vestine,14 give values of wind motions in a very restricted region of alti- le close to 82 km. This technique, however, is sadly limited by the infrequency noctilucent clouds over most of the earth, and their high concentration during summer in high geographical latitudes. The motions appear, however, to meas-

: closely the wind velocities. 3bservations of atmospheric nightglow by various techniques indicate rapid itions in the high atmosphere. Auroral motions, visually and photographically, ige as high as 1,400 m/sec, according to A. B. Meinel,l5 of Yerkes Observatory. radio reflections from auroras, H. G. Booker, C. W. Gartlein, and B. Nichols,"5

Cornell University, find velocities as high as 300 m/sec. In the opinion of Booker I of the majority of the investigators, the auroral motions do not strictly repre- Lt air motions but are more analogous to motions of directed beams. The lower Lit of the auroral activity is in the region of the persistent meteor trains, but the roras often appear at much greater heights. The interpretation of auroral ,tions requires much more consideration in future studies. X closely related phenomenon, in terms of motion, concerns the nightglow ac- ity observed by F. F. Roach and H. B. Pettit,l6 of the Naval Ordnance Test

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Page 4: Evidence for Winds in the Outer Atmosphere

94

" 3

94 -....-- ... . *..

793___ -_.-.- ----' -

92 ___

I.

91 _________ ________ ________

?

89

87

Min. Corr. Factor to Horizontal Velocity =1.0

83

82____

81 -30 -25 -20 -15 -50 -5 0 +5 +10 +15 +20 +25 +30 +35 +40 +45 +50 +55 +60

Velocity (m./sec.)

FIG. 1.-Train velocities, December 23.38, U.T., 1951 (New Mexico; observer, Wells).

.968

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Page 5: Evidence for Winds in the Outer Atmosphere

112

111 - "

110

109 - .

108.

107 - -

105 - " '

104

103 - .s,

102

101

100

98

^9 7 _ * First Exposure 0 to 1s2 .

" o0 Second i3 to 2. .

I 96 * Third 3s5to48 . . e Fourth " 5S6to6.0 fI

95 --- Seventh " 17S7

Min. Corr. Factor to Horizontal Velocity =1.016 .h

93

92

91

90

910 - -----------.--

89

88 -U-

87

86

85 - ( o

84

83

82 -------

81 Vector Towards 30? W of So. <- - Vector Towards 30? E of No.

30 -t1. -120 -110-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 +10 +20 +30 +40 +50 +60

Velocity (m./sec.)

FIG. 2.-Train velocities, March 20.39, U.T., 1953 (New Mexico; observer, Whidden).

969

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Page 6: Evidence for Winds in the Outer Atmosphere

ation at Inyokern. At a height of roughly 200 km., the airglow pattern moves Astward at velocities of the order of 140 m/sec during the evening hours, stops ar midnight, and tends to return toward the east during the morning hours. lis type of motion, similar to that observed for the aurora by Meinel, seems ficult to explain in terms of winds but certainly represents, as do the auroras, )st significant information concernilng energy distribution and flow in the high nosphere. Many visual observations of motion ii the nightglow sky pattern have been ide by C. Hoffmeisterl7 in Germany. At a level near 65 km., C. T. Elvey, now at Fairbanks, Alaska, has recently"5 )orted evidence of motion in the infrared night sky pattern of emission from the I molecule. The pattern as observed at two stations on three nights in 1941 )ved at speeds from 35 to 75 m/sec. This technique appears to measure actual nds in an altitude region which is practically unobservable from the ground by y other known technique, excepting occasionally the anomalous propagation of und. An extensive program of measuring the OH radiation seems highly de- able. Another method of great value for the determination of winds just above the lloon limit is that involving the anomalous propagation of sound. The method Ls exploited earlier, largely for atmospheric temperature measures, by F. J. W.

hipplel8 in England and by B. Gutenbergl9 in Germany. More recently, this athod has been pursued with excellent results by A. P. Crary,2? of the Air Force

Lmbridge Research Laboratories, and by E. F. Cox," of the Naval Electronic

,boratory. Since the temperature maximum at about 50-km. altitude appears ircely hot enough to guarantee the return of sound from a ground explosion, the easurement of sound velocities at high altitudes by a returning signal is highly pendent upon the wind structure at all relevant altitudes. Crary has measured nds at various latitudes from the Canal Zone to Alaska in a height range from 40 60 km. and found velocities as high as 80 m/sec. By means of very heavy ex- 8sive charges in the southwest, Cox has shown striking evidence in the 30-50-

n. level of eastward-moving air currents during winter, and westward-moving 1 currents during summer.

Although the reduction techniques for such acoustic data are extremely com- icated, the method must in principle yield true wind velocities, because relatively tle energy is injected at the altitude levels involved. Crary has well demon- rated the general flexibility of the method for application at various times and at ,rious geographical positions. Many ionospheric techniques in use for the motions of reflecting layers are ex-

amely ingenious, and some of them have been developed to a remarkable degree usefulness. The methodology used by B. H. Briggs, G. J. Phillips, and D. H.

inn,2' of Cambridge, England, is the most complex and completely developed any that have come to the writer's attention. The pattern of ionospheric re-

ction is recorded continuously at three near-by points on the ground and an-

yzed by automatic autocorrelation techniques. The horizontal motion of the fad-

g pattern in the ionosphere directly overhead registers directly. In the E-layer the normal reflection level, Briggs and his associates find a clear indication of

e semidiurnal solar tide, which shows a statistically constant motion of 30 m/see,

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Page 7: Evidence for Winds in the Outer Atmosphere

th the velocity vector rotating clockwise twice in 24 hours. The north-south stematic drift is zero at all seasons, but the east-west component moves eastward summer and westward in winter at about 50 m/sec. In the F-layer, on the other hand, these investigators find no semidiurnal tide but ;her that the east-west component moves toward the east by day and toward e west by night at all seasons. The north-south component is considerably .aller, with some seasonal effects. The average velocities are only slightly greater an those for the E-layer, that is, about 70 m/sec. Further, they find that the locities in the F-layer increase with increasing magnetic activity, reaching values high as 1,000 m/sec during magnetic storms. The direction of such motion is edominantly toward the west. Somewhat similar results via analogous ionospheric reflection techniques have en obtained by J. H. Chapman,22 of Montreal; A. G. McNish,l5 of the United ates National Bureau of Standards; H. W. Wells,15 of the Carnegie Institution of ashington; and by others. N. C. Gerson,23 of the Air Force Cambridge Research boratories, has derived comparable velocities in sporadic-E clouds from ob- 'vations made by amateur radio operators. Although at one time there was considerable uncertainty as to whether the mo- ns recorded by the moving reflection pattern from ionospheric layers represent z true motions of the air in these regions, or possibly some phenomenon analogous the auroral types of motion, the accumulating evidence suggests strongly that

ise motions are indeed very closely related to, if not exactly the same as, the itions of the atmosphere itself, at least for the E-regions. More thorough inter- nparison among the various methods is desirable to establish with certainty the nificance of the electronic measures of motion. We must bear in mind that lfour Stewart's highly valuable dynamo theory of the daily geomagnetic vari- ons requires motions in the ionized layers that can be checked quantitatively th the winds, ion densities, and current densities in these regions. An excellent riew of this attack is given by E. H. Vestine.24 Clear evidence for vertical turbulence arises from other observations. High xing rates, or lack of diffusive separation, are now clearly apparent to an itude of 130 km. from recent rocket measurements by J. W. Townsend,25 of the val Research Laboratory. This fact demands vertical turbulence of a few ters per second, as is also required by M. Nicolet's26 evidence for the lack of atification of the oxygen molecule in the high atmosphere. Hence it is abund- tly evident that techniques for measuring the vertical structure of high atmos- eric turbulence are urgently needed at the present time. HIigh-altitude rockets provide the newest and most sophisticated method of asuring winds in the altitude range from 30 to 80 km. and probably higher. J. Brasefield,15 of the Signal Corps Electronic Laboratories at Fort Monmouth, s had excellent success in'six firings. To measure winds he uses the times and ections of sound travel from rocket-borne grenade explosions at various alti- les. He finds systematic seasonal effects and winds of comparable magnitudes those at higher levels. This method shows extremely great promise, especially en the rocket-balloon combination, the rockoon of J. Van Allen, is used to reduce expense of firings. rhe application of these many techniques during the Geophysical Year should

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Page 8: Evidence for Winds in the Outer Atmosphere

far toward clarifyiing the world-wide circulation patterns in the high atmos- ere. We may expect to increase vastly our understanding of the relationships long the motor sources for atmospheric motions, the ozone layer, the ionospheric ,ers, solar-related phenomena, terrestrial magnetism, and other of the many errelated processes in the high atmosphere. Perhaps such observations will 'e us some clue as to a dynamic coupling between the upper and the lower at-

)sphere, involving meteorology.

In this discussion I am much indebted to H. K. Kallmann,l5 of the University of lifornia at Los Angeles, who made such an excellent report of the first "Confer- ee on Motions in the Upper Atmosphere." This conference was sponsored by

National Science Foundation and was held at the University of New Mexico at

buquerque in September, 1953. Special reference should also be made to the

4liminary statement of a general circulation pattern at high levels by W. Kellogg d G. F. Schilling.27 * This research has been supported by the Geophysics Research Directorate of the Air Force

mbridge Research Center under Contract No. AF19(122)-482. 1 Catalogue gen6ral des etoiles filantes (Paris: Academy of Sciences, 1841). 2 Sidereal Messenger, 1,174, 1882. 3 Astrophys. J., 26, 95, 1907. 4 Ann. hydrographie et maritime meteorol., 49, 294, 1931. 5 Publs. Astron. Soc. Pacific, 44, 178, 1932. 6 Proc. Am. Phil. Soc., 91,315, 1947. 7 Meteoritics, No. 7, p. 95, 1950.

J. Meteorol., 10, 390, 1953. 9 "High-Altitude Winds by Meteor-Train Photography," J. Atm. and Terrest. Phys. (suppl.) indon: Pergamon Press, Ltd., 1954) (in press). ? Proc. I.R.E., 38, 877, 1950; J. Geophys. Research, 59, 47, 1954. 1Phil. Mag., ser. 7, 41, 682, 1950.

Sitzber. Akad. Wiss. Berlin, 40, 1031, 1890. 3 Publ. Unmv. Obs. Oslo, No. 6, 1933. 4 J. Roy. Astron. Soc. Can., 28, 249, 1934. 5 Proceedings of the Conference on Motions in the Upper Atmosphere (reported by H. K. Kall-

nn; National Science Foundation and University of New Mexico, September, 1953) (in press). Mem. Soc. roy. sci. Liege, Vol. 12, Fascs. I-II, 1952.

7 J. Brit. Astron. Assoc., 62, 288, 1952. 8 Quart. J. Roy. Meteorol. Soc., 57, 331, 1931; 58, 471, 1.932; 60, 80, 1934. 9 Gerlands Beitr. Geophys., 27, 217, 1930. 3 J. Meteorol., 7, 233, 1950. 1Proc. Phys. Soc. London, B, 63, 106, 1950. 2 Can. J. Phys., 31, 120, 1953. 3 In H. E. Landsberg (ed.), Advances in Geophysics, New York: (Academic Press, 1952), L55. 4 J. Geophys. Research, 59, 93, 1954. 5 Rept. Upper Atm. Rocket Research Panel, No. 36, October, 1953. 6 1953 (in press). 7 J. Meteorol., 8, 222, 1951.

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