\ itîw ol intersection of logs of Greek letter "gamma" cut in stratus clouds by seeding with dry i c e . Two legs extend out of picture left for a distance of approximately 20 miles, while out of picture rigfit "gamma" pattern describes a loop. Entire pattern is a cleared a r e a some 100 sqiiare miles in size, in cloud
:
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W e a t h e r to O r d e r M. L. KASTENS, Associate Ed/for
Doing something about the weather has now passed from the realm of fantasy to that of reality . . . But now that we can w e are not sure that w e want to do or if w e should
I T is inevitable that man will ultimately be able to control t h e weather in almost all of its particular manifestations. In fact it begins t o appear that ". . . it is much easier t o control the -weather than to predict it." Data now under study by t h e author o f this statement indicate convincingly that i f man has not yet leajrned how t o control t h e weather he has at least b e e n a b l e to incfluence it on a large scale. During 1950 Irving Lang muir, chemist, physicist, Nob>elist, and re cently dubbed "rain-maker" has directed a series of controlled experiments which are unprecedented i n producing colossal efFeots from infinitesimal stimuli. Put with simple bluntness these data indicate that a few hundred grams o f silver iodide dispersed in N e w M e x i c o h.ave changed t h e weather over most of the United States. Climatological data from all over t h e country n o w b e i n g summarized for 1950 indicate that the weather has fol l o w e d the rhythm of a t u n e piped b y peariodic "seedings" i n the Southwest. Xangmuir became one of the first m e n to "do something about t h e weather" thr-ough a rather involved series of events. Laaigmuir's m o s t famous "work, of course,
icreo
has been in the field of monomolecular films and other thin layers. Such films are intimately connected with adsorption phe nomena. Early in the last war w h e n the Chemical Warfare Service determined to improve the smoke absorbing properties of their gas mask canisters they called on Langmuir to make a fundamental study of the absorption of smoke particles. Such a study required a generator which would produce monodispersed smokes of con trolled particle size and predetermined concentrations. To produce such a gadget he called o n his young protege, Vincent Schaefer, w h o turned out a burner-atom izer that was so effective that the CWS had the design scaled-up and put into production as t h e standard military smoke generator. With this project under cc itrol Lang muir and Schaefer shifted to the study of the radio interference caused by the im pact of snowflakes on airplane surfaces. This assignment led to the establishment of laboratories on Mount Washington where heavy snows were frequent and were often driven by high winds. When the interference effect had b e e n effectively characterized as a triboelectric phenome
CHEMICAL
non caused by the multiple fracturing of the ice crystals and suitable recommenda tions had been made, Langmuir and Schaefer w h o had by this time become a recognized research team, transferred to a new project. As a natural successor to their previous work they were asked to convert their Mount Washington labora tory to the investigation of conditions which led to the icing of aircraft surfaces. It was this work which led to their study of the particle size of natural precipitation, the water content of the atmosphere under various conditions, and tshe factors that lead to precipitation of water vapor from the atmosphere. Most important they discovered the prevalence of the water droplet cloud which is supercooled with respect to ice. The next phase of the story is now familiar to any reader of Sunday supple ments. By the time that they were re leased from their wartime job o n aircraft icing, Langmuir and Schaefer were con vinced that in many atmospheric situa tions sufficient moisture was present in t h e air to produce rain but that the rain d i d not fall because of a lack of proper sublimation nuclei. T h e y h a d learned
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tliat all precipitation in temperate /ones originates a s snow. They knew that clouds of w a t e r droplets frequently exist at t e m p e r a t u r e s below t h e freezing point ol water. T h e y determined that in t h e absence of p r o p e r sublimation nuclei, droplets in such clouds will not produce snow crystals spontaneously at temperatures wanner t h a n about —40° C, a n d that when freezing takes place at temperatures below — 40' C , the snow particles formed are too small ( ca. 40 micron diameter) to fall to the e a r t h . T h e y further determined that the concentration of natural sublimation nuclei a t any point in the atmosphere may vary b y a factor of 10 million; a n d that about half of t h e time there is less than the p r o b a b l e minimum concentration of nuclei r e q u i r e d to induce substantial precipitation. All of these data led them to t h e conclusion that it w o u l d be practical under many conditions to induce precipitation artificially b y seeding supercooled clouds with appropriate nuclei. Their first experiments w e r e -with solid carbon dioxide which creates local areas of below - 40° C. temperature, where an enormous n u m b e r of ice crystals are formed spontaneously. When these techniques are applied to cumulus clouds, the crystals are diffused through the clouds by natural turbulence, and they set off a chain reaction which ultimately seeds t h e entire clout! and causes it to precipitate. In the m e a n t i m e another (\V. colleague, Bernard Vonnegut. was seeking artificial nuclei which would be nearly a> effective as ice crystals but m o r e convenient to h a n d l e . Working from the familiar crystallographic principle, he sought a erystal w i t h structural dimensions as close as possible to those of water. Of the readily available compounds silver iodide crystals most nearly approximated the structure of ice. Experimental work confirmed t h e d a t a and Vonnegut found that very small crystals of silver iodide would induce crystallization in clouds as warm as — 5 e C. He designed a generator to produce large quantities of sil\er iodide smoke h a v i n g very minute particles, utilizing some of t h e principles developed by Langmuir a n d Schaefer in their work on smoke generators. H e was thus able to produce a fine smoke of silver iodide containing a b o u t 10 14 nuclei per second. The salt is fed into the nozzle dissolved in a sodium iodide in acetone solution. Hydrogen g a s is u s e d as a propellent a n d auxiliary fuel. Using a very dilute solution, the smoke generator disperses about 40 grams of silver iodide per hour. Ready to Begin W i t h these two seeding media t h e team of L a n g m u i r , Schaefer, and Vonnegut were well e q u i p p e d to study a n d alter the atmospheric phenomena associated with precipitation. Carbon dioxide was more efficient a n d could be more accurately controlled. Silver iodide h a d t h e advantage of greater persistency and it could b e u s e d without flying into t h e turbulent storm-breeding areas. T h e exV O L U M E
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periments with these materials proved to everyone's satisfaction that it was possible to alter cloud structure and generation. They proved t o almost everyone's satisfaction that rain could be induced artificially. However, they failed to convince some of the professional meteorologists that "it wouldn't have rained anyway." Run-off data, time-lapse movies, precipitation measurements, and the discredited forecasts of the professional weathermen, were all answered with, " T h e synoptic situation at the time of the precipitation could have produced rain. The seeding experiments simply advanced the onset ol the rain." Langmuir. Schaefer, and Vonnegut wenconvinced that they had discovered a technique of great potential benefit to man. However, they also knew that the> would have to prove it before it would Incompletely utilized. They were faced with a system containing a large number of variables which could not be controlled. They could not t a g the rain they produced with radioactive tracers because the concentrations involved (roughly, 1 mg. Agi per cubic mile of air) were too low to he detected. However, they could apply a technique becoming increasingly familiar to physical scientists—statistieal analysis. No Periodicity Noted Pre\ iously Many meteorologists over the years have attempted to detect soi ne periodicity in weather phenomena. However, except for the daily and annual cycles they have failed to detect any regularly recurrent pattern. Consequently, Langmuir suggested that a given area be seeded at regular intervals with a fixed amount of nuclei regardless of the synoptic or cloud conditions. Any statistical evidence of weekly periodicity in subsequent weather data could then be attributed directly to
the effects of the seeding. They recommended that the seeding be done with silver iodide generated as a ground smoke because of the ease with which this type of seeding could be accomplished and the greater persistency of the nuclei. The seeding was done on a seven-day cycle to simplify scheduling. Also the period ot influence of any particular weather condition on the weather which follows it seems to b e of this order of magnitude. They those New Mexico as the site of tin experiments because the Southwest can use all the· precipitation it can get and there was little likelihood of local objections to the work. Also the area was a potentially fertile one for seeding since none of the naturally occurring sublimation nuclei were effective at above - 1 5 (*. and less than 10rV of the potentially rain-producing clouds attained altitudes where temperatures lower than this prevailed. Furthermore, the Rio Grande valley is in a cyclogenetic or weatherbreeder area a n d the experimenters were curious to determine the maximum area of ehVctivcncss of silver iodide seeding. T h e periodic seeding was begun in Deccniher ot 1949 by Project Cirrus jointly sponsored by t h e Signal Corps, t h e Air Force, and the Office of Naval Research and is still continued. Seeding experiments conducted in New Mexico during the previous two years had given strong indications of a long range effect. Precipitation data revealed that there was indeed a pattern of rainfall that fanned out across the state downwind from t h e site of the seeding and in some cases it seemed possible to trace the wave of rainfall on up through Oklahoma and Kansas. Judging from t h e time of the rainfall t h e precipitation stimulus was traveling about 20 miles per hour. Considering the rate of travel and the distances involved it was still possible that this precipitation was
Vincent J. Schaefer prepares to make a miniature snowstorm in a freezer compartment, while Irving Langmuir, a n d the third m e m b e r of t h e "weather-making" team, Bernard Vonnegut, look on
* > MARCH
19,
1951
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DAILY PRECIPITATION
ILLIKOIS APRIL 1 9 5 0
Day of month Station Albion Aledo A l e x i s l a t e r forks Alton Due 26 Ann* 1 XV Ann***D Aatlocb Auffustt B l g h School Aurora C o l l e g e Barry l i t e r forks
.87 1 . 9 5 .58
R
1.60
.63 .75
Beardetown Beardstown Lgrng Daa R Belvldere· Sewage PI . R Bentley Beaton BlooBlngroo Korea 1 Bluffs Bradford CAA U> 6 Brookporx. Daa 52 Cairo »B C l t j Ζ
Chicago S a n Dlst D l s p Chicago S a n 01st Off Chicago S Filter PI Chicago Sprgfld Puap Chicago WB Airport Chicago WTB City Chicago u n i v e r s i t y C h i l l lc»Xbe Cicero Cisne B r o w Ctap Clinton a S Coi'lttrrlue Crete Danville Danville Hospital Danville Sevige P l a n t Decatur Des P l a i n e s 1 Κ* Dloaa Dlron
R R R R Ζ Ζ Ζ
.06
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19 . 20
.12,
.26 .24
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.12 .15 .52 .83 1 .06 1 .55 1 . 1 0 .79 .63
.60 .52 .02
.60
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R R R
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.35 .10 .08 .15 .58 .24 .68
. 5 1 1.44
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Official weather bureau chart of daily precipitation indicates seven day cycle tendency caused by the actual nuclei dispersed near Albuquerque. However, in the spring of 1950, after the periodic seeding had been in progress several weeks, heavy rains in the Ohio River Valley began to command consid erable attention in the popular press. From these reports Langimiir a n d Schaefer began t o suspect that the heaviest of these rains were occurring at seven-day intervals. Detailed examination of the weather d a t a strengthened these suspi cions. T h e experimenters immediately recommended that t h e amount of silver iodide used in the seeding operations be reduced a n d requested that Project Cir rus appoint a committee of meteorologists to examine their theory. After examina tion of die data the committee declared the apparent correlation accidental and full scale seeding was resumed. However, Dr. Langmuir was not convinced and began a close analysis of precipitation data, from throughout the country. N o w with almost an entire year's data available h e reports that almost every state in t h e union has experienced a cer tain degree of seven-day periodicity in its weather since the periodic seeding was begun. T h e effect is naturally most pro nounced in the Mississippi and Ohio River states which normally receive their weather from the A l b u q u e r q u e "weather-breeder." Furthermore, this periodicity applies to phenomena other than precipitation al though the occurrence of rain is the most spectacular effect. Statistically provable, 1092
seven-day cycles can b e determined in pressures, humidities, cloudiness a n d tem peratures. All of these cycles prove to have the same seven-day periodicity. Detailed analysis m a d e of high-level temperature readings, for April of 1950 revealed m u c h better than random cor relation with a seven-d^y cycle for points as widely scattered as Chicago, 111.; Omaha, Neb.; Columbia, Mo.; Oklahoma City, Okla.; Buffalo, Ν . Υ.; St. Cloud, Minn.; Nashville, Tenn.; Washington, D. C ; and Charleston, S. C. Chicago showed t h e highest correlation coefficient; 0.782 for the 28-day period. T h e Chicago data is given below along with the calcu lated cycle adjusted to the phase of t h e data. By treating the correlation coefficient by the equation SF =
1 (1
_
Γ»)
«.5
w h e r e r = correlation coefficient, a n d t h e exponent, 12.5, is determined b y t h e number of d a t a a n d t h e degrees of free
dom, it is found that the o d d s against such a cycle occurring by c h a n c e are about 3.4,2f>. T h e other d a t a give almost e q u a l l y impressive evidence against an e x p l a n a tion of t h e recurrent cycles as accidental. Examination of data from previous years has not revealed a single instance of sig nificant correlation with a seven-day cycle, when treated by identical statistical tech niques. F u r t h e r details of the statistical techniques used b y Dr. L a n g m u i r a r e given in an article, "A Seven-Day P e r i o d icity in W e a t h e r in United States d u r i n g April 1950," which a p p e a r e d in t h e D e cember issue of the Bulletin of the Ameri can Meteorological Society. Of course there is no possibility t h a t these effects a r e d u e to t h e physical trans port of t h e nuclei seeded in New M e x i c o . However, there is a well established meteorological theory which postulates t h e existance of "weather oscillators" which generate waves, perhaps of pressure, which determine the weather over large areas of the globe. GE's rainmakers t h i n k t h a t the experiments in N e w Mexico m a y h a v e
Daily T e m p e r a t u r e s ( 1 0 P . M . E.S.T.) in D e g r e e s C e n t i g r a d e at 850 m b L e v e l over Chicago during 28-Day Period ( V I ) April 2 to 2 9 , 1950
Average: Observed Calculated
Sun. + 6.3 + 0.8 4- 8.0 4-14.2
Mon. + 3.2 4 9.2 4 7.2 410.2
Tues. 11.2 4.2 1.8 4.8
Wccl. - 7.2 -14.2 - 4.8 - 1.5
Thurs. -2.8 -9.2 -4.0 -6.5
Fri. 4-5.2 -7.5 +0.2 + 1.8
-f 7.3 4- 8.9
4 7.4 4 5.4
2.2 1.4
- 6.9 - 6.5
-5.6 -6.0
—0.1 —0.2
4 1.8 4 4.2 412.8 4 7.8 4 6.7 4 6.4
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existence of "weather oscillators'* which triggered such a natural condition. T h e oscillator theory of the effect is supported by the fact that when weekly seeding* were skipped the periodicity did not show a gap but the peak was usually delayed about 24 hours. However, no one us yet has presumed to oiler a complete explana tion of these newly discovered long range effects. The significant point at this state is that the phenomenalogical evidence seems to be irrefutable. Full Significance Not Yet Realized T h e practical significance of these dis coveries is not yet fully revealed. It is, perhaps, not correct t o say that rain can be "created" but it may b e pos sible to adjust tlie frequency and to some extent the area of rainfall. If the area of precipitation can be moved from the valleys to the mountains, hydroelectric potential will be increased. If it can b e brought from the ocean to the interior of continents, deserts may come fertile. Con versely experiments already under w a y in tropical countries indicate that it may b e possible to reduce either the frequency or intensity of the rains in those areas to make them more adaptable to agriculture. A representative of the Chilean govern ment has already visited this country t o investigate the possibility of increasing the rainfall in his country's arid northern valleys «by regular seedings. Since this area has ample cloud formations the proj ect w o u l d seem to be feasible. In all these cases the long distance as pects of weather control m a y be more promising than the local "rainmaking" which has thus far b e e n the extent of at tempts at weather control. It is true that wheat growers around Prosser, W a s h . , say they increased the value o f their 1950
wheat crop b y $ 7 5 0 , 0 0 0 through the use of professional rainmakers. Cane growers in Louisiana have conducted experiments with "planned precipitation" which they say are very satisfactory. Both cattlemen and dirt fanners in the western plains states report success with the technique. One rancher said that last summer's in duced rain was worth $ 1 5 million to Baca Counts-, Colo. This winter a 400mile stretch of the Continental Divide will b e seeded to increase the snow peak. In 1949 pear growers in Oregon's Rogue Hiver Valley attributed the second hailfree season in history to seeding opera tions. T h e California Electric Power Co. credits three years of seeding with increas ing their hydro-power output by 14,300,000 kw.-hr., at a cost of about 1.5 mills per kw.-hi. As a n incidental result they say they produced an extra 6,500 acrefeet of water for the city of Los Angeles and q u e n c h e d at least o n e forest fire. There have probably been other success ful applications but commercial practi tioners of the n e w science are notably reluctant to advertise their results because of the as yet unresolved legal status of mamnade precipitation. T h e rainmakers are adamant o n o n e point, however. They insist that their induced rain is not taken away from adjacent areas. Their conten tion is that n o rainfall removes more than l*"r of the moisture from the air and so cannot effect the chances of rain in other areas. However, all known rainmaking at tempts have experienced the difficulty of pinpointing the area in which the in duced precipitation will fall. If this prob lem should prove insurmountable it will mean that artificial control of precipitation will h a v e to be done on a broad area basis, and perhaps with a goal of long
Dr. Vonnegut uses charcoal burning generator t o dispense stream of silver iodide particles into the atmosphere at rate of one hundred million particles per second
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range results. If this should prove the case then the "long-range effect" n o w b e ing elucidated by Langmuir may prove to be the most practical instrument for economic control of the weather. Legislative Action The broad area aspects of this technique have already been reflected in the halls of Congress. On January 3 Representative Thomas II. Werdel ( R., California) sponsored a resolution calling for the creation of a joint congressional committee to study the effectiveness of cloud nucleation and the need for an agency to develop and control the use of i h e technique. The House Committee on Rules, to which this resolution was referred, has taken no action to date and has none scheduled in the immediate future. On January 8, two bills were introduced in the Senate, o n e sponsored by Senator Clinton P. Anderson ( D., N e w Mexico) "to provide for the development and regulation of methods of weather modification and control," and the other by Senator Joseph C. O'Mahoney ( D . , W y o m i n g ) which provides, in part, for the conducting of "operations for producing water from the atmosphere." Both Senate bills provide for assumption of liability b y the government for damages caused as the results of such "operations." On February 5, 1951, Senator Francis Case ( R., South Dakota) introduced a bill to "Authorize the Secretary of Agriculture to conduct research and experiments with respect to methods of controlling and producing precipitation in moisture-deficient areas." The three bills of Senators Anderson, O'Mahoney, and Case were referred t o the Senate Committees on Interstate and Foreign Commerce, Interior and Insular Affairs, and Agriculture and Forestry, respectively. T o facilitate the handling of these related bills, the respective committees have appointed subcommittees. T h e three subcommittees have scheduled joint public hearings o n the over-all subject starting on March 14, 1951. Now that this start has been made, additional legislative and legal action defining the liability of cloud seeders may b e expected. General Electric has, for its part, offered royalty-free use of its rainmaking patents to any research investigation. As this n e w science continues to prove its effectiveness and t h e legal hurdles are cleared away or at least defined w e may expect "synthetic" or "experimental" meteorology as it has been variously called, to begin t o "do something about t h e weather." It is certainly true, as t h e meteorologists contend, that t h e synoptic conditions create the weather and the local rainmaker c a n only produce rain if the local atmospheric conditions are propitious. However, something must make the synoptic conditions. If t h e experimental meteorologists can learn to modify weather oscillators then it may indeed b e come "easier to control the weather than to predict it."
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