Show nucleation Proceed ure explained this is the me second in a serle series of six fix articles artiles on iraln makan J by living irving P krick the term rainmaker rain maker is not entirely accurate in n the ceic rl tion of the engaged in cloud se seeding iding or artificial nucleation clea tion no one can C lakeit ma keit rate when it going to rain anyway what the meteorological scientist can do is to help nature i along py by increasing the volume of rainfall available from any favorable cloud formation the scientist cannot however make rain min fall occur unless conditions are such that some rain would have fallen from the clouds without his help the scientist can increase the volume of rain th atwill fall during a given storm in ratios ranging from 50 rex per cent to per cent he should be called a rain increaser rather than a rain raia maker cloud claud seeding from ground generators can best be explained by first undertaking a description I of how rainfall occurs in nati nature lre every raindrop that falls from the clouds from a storm has been formed around a tiny particle or of solid substance th s could be a t tiny my speck of dust drawn from the earths surface by gusts of wind it could bs be a miniscule pie aws e of loam or quartz or any one df or hundreds of other particles invisible to the eye but constantly floating through the atmosphere before any such particle can function to mahe rain it must encounter a super cooled cloud whose i interior temperatures are belon freezing I 1 I 1 these various particles are able I 1 to neu cleate or draw moisture to themselves at varying temperatures depend depending iniz upon the character of ohp hartcle part cle As thy float through tie the eky y an ana enter clouds of consider consi deraNe aKe moisture contort content these dinv particles are ready tr to I 1 ago go to work provided the temper of the cloud is actable aa table to t their particular nu I 1 needs minute very cold water droplets droplet that have ben been flo floating atiniz inside the clond are drawn abou I 1 these nuclei retting etting up a chal chait reaction wh ch att acts add aidt ional moisture when tho particle has surrounded iosef with sufi sufficient clent m moisture it becomes a small lea ice crystal or anor flake of sufficient weil ht to fall fron from the sky toward the Rr arolyn olyn if te temperatures below the are below belov i freezing then it re ches the earth as a snow hike if th thi i tempera tures ere re above freezing it melts and falls as a braind o on in any rain or snow torm this process is repeated literally billions of tip tines es now let m whit h at happens wh iodide are inu t U od P d into the rhoud to sup plemert plemer lt the work done by nature continued on page 6 dr kmicic continued from page 3 an in supplying those clouds clouda with tiny particles which will ultimately become first ice crystals then either snowflakes or raindrops the silver iodide generator is essentially a simple device small quarter inch particles of boundary foun dary coke axe are soaked in a liquid solution of silver wide iodide carefully prepared and weighed so that the volume of 0 silver iodide in each pound of coke Is definitely known i to the supervising meteorologist these small pieces of coke are thien then put into a firey crucible equipped with a blower and heated i to a temperature of between 2500 and degrees fahrenheit fahren helt at that temperature silver iodide is expelled from the crucible as a gas and forced upward into the atmosphere by the blower immediately inedia tely upon reacel reaching F the colder outside air this gas which is invisible becomes literally billions upon billions of tiny particles of solid silver iodide crystals the output from the generator is regulated at about thirty quadrillion tiny particles of silver iodide per min 1 ute each one of which will be e a L wu potential ice part particle acl when it t reaches the super cooled cloud toward which it is projected because the generator is used only during times of likely storm when there is natural turbulence coupled with abnormal updrafts up drafts inthe iri the air these particles are quickly swept aloft and into the clouds it has already been mentioned that the particles introduced by nature into the clouds attract moisture and become ice crystals at varying temperatures some of them nucleate at temperatures kofl of zero degrees fahrenheit or con sider ably bly below the great ad 1 vantage of silver iodide is that its particles begin to attract moisture at a temperature of approximately 25 degrees fahrenheit thereby functioning at much higher temperatures than most of natures particles in nature the lower temperatures adapt adaptable abl for nucleation by natural ex 1 normally only at high atmospheric i levels because silver iodide functions at higher temperatures it is thus able to wring more water out of clouds thin than would fall naturally by acting upon thel moisture in lower portions of a cloud mass it is important to that raindrops or snow flakes in ii the areas in which this method metho is teal always beggi beg first a as 3 ice crystals in super cited cooled alo lodi d A silver iodide particle wll will form an ice crystal at a temperature 1 of 25 degrees F whereas a pirt icle of clay dust will not draw moisture to it unless the temperature of the cloud is zero F thus the advantage of sir silver iodide that in brief is the story of artificial nucleation through the projection of silver iodide particles into the air from ground generators tors although this explain aaion has been somewhat over simplified all the essential facts are here it would be a perfectly normal question for you to ask if its as simple as that why must the work be undertaken uni un i der the supervision of a meteorologist experienced in the technique why a rancher build a venerator Rene himself buy some silver iodide then oplie a chance of any clouds on almost any day until he succeeds in making the volume of rain falling on his land increase 01 the answer is that the work must be attempted under the guidance of an experienced meteorologist eor because unsupervised seeding can actually d er crase ase the volume of normal rainfall that would have occurred bv over seeding for example with too many particles particle of hilved iodide for the available moisture of a given cloud so many billions of minute crystals fire are formed that the moisture of the cloud is exhausted in becoming 9 ice crystals i so 90 small that they do not have continued on page 7 dr krick 1 continued from page 6 i enough weight to fall from the sky A meteorologist trained in the technique of cloud seeding can measure this moisture potential and is able to judge how much silver iodide should be projected furthermore the most advantageous sites for the generator can vary from storm to storm and the trained mete orol fists knowledge of surface an and upper upper air wind currents is important in choosing the sites best suited for actual seeding operations under any given condition just as you cannot use high octane gasoline in a kerosene motor so you must measure the volumes of silver iodide to be used under varying conditions that is why the presence ot of a meteors meteoro meteorologist I 1 ogis t with both field experience peri ence and la laboratory borato ry experience is imperative in this work |