Omaha daily bee. (Omaha [Neb.]) 187?-1922, August 22, 1915, EDITORIAL SOCIETY, Image 19
The Omaha Sunday How tbe Rising Hot Air Currents Start the Formation of a Thunderstorm. A 1 Cross 8ectlon of a Thunderstorm. (A) Rising Hot Air Currents. (B) De eending Cold Air Currents. (C) The Storm Collar, a Constriction Which Produces Violent Winds. (S) The Roll Scud, or Hot Air Driven Upwards by the Cold Descending Current. (D) Wind Gust. (H) Hall Produced by Ice Particles Blown Up and Down In the Cloud. (T) Where the Thunder and Lightning Appear. (R) Rain In the Thunder Cloud (R1) Rain Produced In Adjacent Cloud. Science at Last Penetrates the Mystery of Cyclones, Tornadoes, Cloud-Bursts, Thunder and Lightning, Which Have Heretofore Been WHY do we have thunderstorms ( toward the close of a hot Sum- A UZZlljalS? mer's afternoon? Many features of this familiar occur- TT JL rence have not been clear even to sclen- lVJl VSlCITIGS tlst.s, and Professor William J. Humphreys, J the well-known meteorologist of the United States Government, has recently furnished' Rome interesting information on the sub ject. The rain of the thunderstorm occurs because the earth, heated much more rap Idly than the upper air on a hot Summer's day, sends a violent current of hot surface air into the upper region. This current gathers moisture as It rises, is finally cooled, and then falls In the form of rain. Why thunder and lightning accompany the storm is a more obscure matter, and is explained by Professor Humphreys by a description of a recent experiment in which a minute thunderstorm was pro duced. Thn exnerlmrnter allowed (Irons of distilled water to fall through a vertical Diane oi air ot sunicieui gtrcngui to lnouuce spray. From this the following facts were ascertained: 1. The breaking of drops of water is accompanied by the production of both negative and positive ions (the particles of which electricity is composed). 2. Three times as many negative ions as positive are released. Now this experiment closely reproduces the conditions that produce a thunder storm. Such a storm is characterized by strong upward currents of hot air. aud these are strong enough to account for the breaking up ot all rain drops which would otherwise fall through them. Hence at the top of the uprushlng air current of the storm, 1. e., within the thundercloud, a rapid electrical separation goes on, the first result of which is positively charged rain drops and free negative particles. The positive charges of the rain drops are con tinually increased by the successive dlvi slon and union of the drops. These posi tively charged drops fall to the earth when ever the air current becomes weak enough to permit their passage. The negative particles are carried up Into the higher part of the cloud, wher they unite with the cloud particles and facilitate their formation into negatively charged drops. These ultimately fall in the gentler rain of the storm. The reunion of the two separated forms of electricity produces lightning. Any weather condition In which a layer oi warm air is beneath a layer of cold air is likely to give rise to a thunderstorm if the temperature contrast be strong enough. Buch a situation is unstable and leads to the violent moving about of different strata of the air, which is the essential feature of a thunderstorm. The storm may arise from intense local beatlug of the earth's surface. In which case it is knows as a local or heat thunder storm, or from the over-running of one layer of air by another at a different tem perature. Thunderstorms may also result from the under-running, and consequent uplift, of a saturated layer of air bv a denser layer. Non-local types cf thunderstorms are classified by the wc.ither experts as cy clonic, tornadic, an'l-cyclonic and border thunderstorms, ucio.din to their position with respect to cyclonic and anti-cyclonic formations In th a-i.io-i.!'ere. A line or row of tornalic storms extending from a cyclonic te.it re constitute the well-known "line snua'.l." On land thunderstoms occur most fre quently In the esr!y afternoon and in Sum mer, and at sea they are most frequent at nitsht and in Winter. This is because the relative temperature :t the air as com pared wlh land aud with water at the two seasons is reversed. Thunderstorms are more frequent In warm and wet years than in cold and dry ones. Heat is the determ ining factor in producing them, and con sequently they ore most frequent at the period of minimum sun spots and least frequent at times of maximum sun spots. Professor Humphreys explains the struc ture of a typical thunderstorm in a very interesting manner. First we have sir L 1W flowing in from all sides, rising, cooling by expansion, and building up the thun dercloud. As a result of this process rain is formed at a considerable altitude where the air is quite cold in fact, so cold that hail Is often formed. This cold rain, or a combination of rain and hall, as it falls to tho earth, chills the air all the way down to the ground, partly as a result of its low temperature at the start, and partly b-L-ause of ttw evaporation that takes place during its fall. This cold current of air Is correspondingly dense and becomes a strong downward current The frlctlonal drag of the falling rain is an additional factor in giving it this downward move ment. The current plunges down and at the same time is carried forward by the gen eral movement of the storm, under-running and buoying up the warm adjacent air in front. This current Is a typical thunder squall, which rushes forward from an ap proaching thunderstorm, agreeably cooling the air. Between the uprising sheet of warm air and the adjacent descending sheet ot cold .iir horizontal funnels are formed, in which the two currents are more or less mixed. These become visible at a point near the front lower ed?e cf the main thundercloud, where the rising air has eo nearly reached 'he rain point that the somewhat lower temperature produced by the admixture of the descending cold air is sufficient to produce a fog-like condensation. This constitutes what weather experts call a nail cloud" or "roll scud." Tiiese are the stages of a thunderstorm in order: (1) An abrupt fall of tempera ture, due to the rain-cooled descending urrent; (2) a sharp rise of barometlc temperature, which Professor Humphreys believes to be due to lower temperature, decreasing humidity and other more ob scure factors; (3) a violent gust of wind or thunder squall, already referred to; and (4) initial heavy rata of the storm. .The name of "rain gush" is given to a . sudden acceleration to rainfall immediate ly fallowing a heavy clap of thunder. The uxi ...nation is that excessive condensation In tue thunder cloud leads to a local ex cess of electrification and electrical dis charge, sine the latter processes depend upon the presence and abundance of water ' Ibt SMmmer After mooms t How the High Buildings r I. 4 t . ,1 a " Photograph of a Thunder storm in Course of Formation Taken from a Balloon. . - h .a t-i 'H.V f v7 .-7.1 lrops Hence excessive condensation or rain formation really precedes the thunder slap, but as sound travels faster than rain falls we hear tbe. thunder before the rain push reaches us. When the descending current of rain is very heavy, the drops being so large and close together that they form an almost continuous sheet of water, we have what is known as "a cloudburst." They usually occur over very dry sections of country which have sent an unusually strong hot air current rushing up into the cold air region. Cloudbursts are often very de structive, especially in hilly country, where the entire fall of water floy suddenly into the tiearby valley. Hall, which Is a phenomenon of severe thunderstorms, consists of roughly con centric layers of tnow and ice. It can only be formed In the upper part of a thunder cloud, where both snowftakes and excessively cooled water drops sre present. The nucleus of the hailstone having been formed in this cold region gets into one of th upper weaker undrafts of the storm and fall fo the level of liquid drops, where its own low temperature enables it to gather a coating of ice. Presently a more violent upward puff carries it aloft strain, and it acquires a coating of snow. This process may be reneatcd several times, until the halftone U too heavy to be supported by ascending currents and falls to earth. Itpcent photographs of the lightning flash by scientific observers have done . much to elucidate the real shape of this startling l henomennn. It Is now known that the old, popular and artistic concep tion of a zig zag streak of lightning is mis taken, and that the fash has several typi cal forms, all quite different from this con ception. The fact is. of course, that a llghtnin? flash Is so dazzling that the hu man eye ran not obtain an accurate im pression of It. The photographs show that most often the lightning flash fills itself up gradually, and consists of several successive dis charges along the same path. The dis charge differs from that of an electrical machine in one important respect the dis tribution of the charge. In the case of tho machine this takes place almost wholly on the surface of the apparatus, while In that of lightning It is Irregularly dlstrlb- Copyright, 1013, by the Star Company. Bee Magazine Page of Now York and the Narrow Streets Between Them When Superheated Particularly Violent Thunderstorms. ' ' k ' ' i( . .. . S , ' ... " . J . 7 v " . . I-. liaitWyyiW. v t ' ' ' " Remarkable Lightning Effects Photographed During a Thunderstorm uted throughout the cloud. In both cases, however, the air must be charged with particles of one kind of electricity before the discharge can take place freely. This condition at times seems to establish It self gradually. According to Professor Humphreys's view the lightning spark, once started, "Ionizes" the air and makes Its own con ductor as it goes. A similar condition can be produced on a photographic plate by bringing in contact with the film some dis tance apart two conducting points attached to the opposite poles of an electrical ma chine, "lirusb" discharges develop about each point, but the glow at the negative pole detaches itself and slowly meanders across the plate toward the positive point This explanation furnishes a possible clue to the cause of "rocket lightning," which is a flash progressing slowly across the sky line a sky-rocket and of "ball light ning." Professor Humphreys has investigated the question whether lightning is unidirec tional, i. e., flowing In one direction or oscillatory. He has come to the conclu sion that it Is unidirectional, for the fol lowing reasons: (1) Lightning operates telegraph instruments; if these discharges were alternating it would not be so; (2) at times it reverses the polarity ot dyna mos; this requires a direct and not a high frequency alternating discharge; (3) the oscillograph shows each surge or pulsa tion, as well as the whole flash, to bs flowing In one direction. If the day grows excessively warm and toward evening the clouds seem to rest on the western horizon and become grayish at the base, if the wind dies away and the atmosphere seems unusually quiet, it is the best evidence of a coming thunder storm. Thunderstorms are more dangerous over waterways than over dry land, because water is a good conductor ot electricity. Over a river the lines ot electrical force are concentrated between tbe low-lyinz clouds and tbe water, which creates an electrical disturbance of greater energy than is observed over the land. Why Many Go-Carts Are So Bad for Babies T 'HE choice of a vehicle for the baby is a matter of great importance. The folding cart, which may be taken on the street cars, permits mother and baby to go out many times when it would not otherwise be possible. The great convenience of this cart cannot be denied, but such cars should be used only for the purpose for which they are intended, namely, to cenvey the baby short distances, and not as pleasure veh icles, nor should the baby be left to sit fastened In one of these small carts for any great length of time. Some of the go-carts of the present day are so small., so stiff, and so 111 adapted to the baby's anatomy that they can Qreat Britain Rights Keetrvsd 'MM&er "H , . ... , A cyclone occurs at an area of low pre I- of one hundred to two hundred miles be sure that is, where the atmospheric pres- fore it is dissipated. sure is least, or where the barometer reads The explanation of a tornado is that the lowest, and is nothing more or less than a comparative vacuum In tbe atmos phere, into which the winds from all sides blow. The system of winds established by blowing toward the low-pressure centre Is called the "cyclonic system," for the rea son that they blow spirally inward and up ward, with a motion contrary to the direc tion of movement ot the hands of a watch, and when nearlng the centre the spiral motion becomes more pronounced. The storm centre Is known by sailors as the "eye of the storm." At the centre of tbe cyclone the atmosphere for an hour or two In tbe most extensive storms be comes clear, the clouds disappear, the barometer shows a slight rise, and to all appearances, except to the experienced ob server, tbe storm is practically over. This condition changes after the storm centre passes, when the wind shifts from the easterly quarter from which It has been blowing to a westerly one and attains a greater force. This peculiar phenomenon Is due to the ascending current of air at the storm cen tre being dissipated by a descending cur rent from higher altitudes, thus prevent ing the formation of clouds at that point. The tornado Is the smallest and yet the most powerful and destructive of all storms. It is of local origin, limited In width and length of its path. Its chief characteristic is a funnel-shaped cloud, which dips to the earth's surface and has a violent rotary motion. The upper surrounding sky is covered with a mass ot black, treacherous looking clouds. A tornsdo and a cyclone are very different formations, and are only alike In that each is a storm of whirling motion. The cyclone is a wide-area storm, covering flv hundred to two thousand miles, with brisk to high winds extending from its centre to Its outer edge. Tbe tornado Is only from fifty to a thousand feet wide and usually travels a distance hardly be recommended even for tem porary use. Also, they are so close to the ground that tbe child is propelled through only the lower and colder air currents, which fling an unending stream of germ laden dust off the street into his face. They frequently have no cover with which to shield the baby from the heat or cold, or sun or wind, and in cold weather It Is impossible to keep baby sufficiently warm In one of them. The best vehicle for ordinary use about the borne Is one which Is at least two feet high. It should have room for the baby, with the necessary wrappings, in any position, and a cover that can be readily adjusted to secure the needed protection. It should have strong, well balanced in Summer Cause , ; ..v-..-'vi . 'V r n at Sea. when an area of low pressure passes over the country the general circulation of winds from all sides flows toward Its cen tre, which brings the colder, dry winds from the north and west, and the warmer, moist winds from the south and the east into the general circulation of air bearing toward the storm centre. It Is believed that In this rush of warm and cold air there must be a point of meet, ing where there Is a great difference ot temperature. In tills general case the war mer current uuderruna the colder layers of air, and In seeking an outlet forces Its way through the place of least density, causing a violent upsetting of the atmos phere, which results in the formation ot a funnel-shaped cloud of condensation of moisture from tbe uprushlng ot warm, moist air. The greater the difference In tbe temperature between the warmer and colder air layers tbe greater will be the violence of tbe rotary motion which takes place at the vortex. A tornado as it advances produces a ter rible roar, which has been compared to the , noise of thousands of trains ot cars pass-' ing through a tunnel at the same time. This terriflo noise usually occurs about fifteen minutes before tbe arrival of the tornado, and elves warning of its approach. It Is probably due to friction caused by the violent rotary motion of tbe tornado fun nel. No power has ever resisted the force ot a tornado except a mountain range. To be within the tornado path is almost cer tain death. On tbe south side one may stand within a distance ot five hundred feet with impunity, but on the north side It Is almost certain destruction to be with in a thousand feet The tornado uproots trees, blows down houses, lifts bridges and large buildings from their foundations, blows trains of cars from their tracks and lifts them several feet In the air before overturning them. springs and stand squarely on four wheels. .A safety strap which fastens about the baby's waist gives greater pro tection than the ordinary carriage strap. Carriage outings are, at best, not an unmixed advantage to the baby, although often they afford the only available means of his getting the out-of-door air. The lack of exercise and tbe more or less rigid position maintained for considerable periods ot time serve to tire the baby. Also It is no doubt true that a baby sent out in charge ot another child or ot some person not altogether competent to Judge ot his comfort la often neglected. A more wholesome and natural place for the baby to take his airing is In the yard or on the porch, where he can be under the mother's supervision.