The electric discharges occurring between clouds or between a cloud and the earth and being in the form of a lightning and a thunder are called as a thunder-storm (see the Thunder). What is the phenomenon — electric, was for the first time proved by Franklin in 1752 (see the Lightning rod). Thunder-storms ordinary are followed by a heavy rain, strong whirls of air, frequent a hail (see the Hail) and considerable fluctuations of temperature and humidity, rarely snow. The thunder-storm is preceded ordinary by high temperature and the large amount of water vapor which is a consequence of it in air.
Clouds in which there is a thunder-storm, belong to cumulo-nimbus (see Clouds). They consist of the cloudy masses which is heated up at each other which basis has an appearance of an even layer gray and lead, sometimes very dark, almost black color with yellow, blue and other shades which reason, most likely, consists in various thickness of clouds; other part consists of white cloudy heaps with the grayish middle; edges of thunderclouds at solar lighting seem brilliant white that makes sharp contrast with the dark basis. At top storm clouds quite often pass into the clouds reminding plumose (so-called lozhnoperisty).
In most cases height of storm clouds is small: on average a conclusion their basis is at the height of 1400 m, top — at the height of 4000 m. That circumstance that the real plumose clouds which average height about 9000 m observed sometimes over storm don't take part in that movement which happens during a thunder-storm in the lower layer of air is explained by such insignificant height of storm clouds, by the way. Geographical distribution of thunder-storms very unevenly. It depends on distribution of temperature and amount of water vapor, on rainfall, and also local conditions, as it is clear as thunder-storms are a consequence of the ascending air movements.
In total happens thunder-storms in the rainy tropical countries more; so, in Beytontsorge on the island of Java in a year more than 160 days with the thunder-storm (A. I. Voyeykov, "Meteorology", 1891); in Guiana and Venetsuele in a rainy season the thunder rattles nearly an every day all day long. In midlatitudes of a thunder-storm is more rare; so, in France their average happens 16, in Italy 38, in Bavaria 20 in a year. Behind polar circles they are extremely rare; often pass the whole years without thunder-storms. The most northern thunder-storms were observed during especially hot summer in the Kara Sea and in the western part of Spitsbergen in latitude 78°.
There are no thunder-storms in the countries of a drought, e.g. in extensive Asian and African deserts, in Lima and so forth. In areas of trade winds they happen only in those days years when hurricanes dominate, being indispensable satellites of the last. These thunder-storms are remarkable by the unusual force of electric discharges: lightnings sparkle continuously, the thunder rattles with a terrible force, fireballs (see the Fireball) in all directions plow the sky. In areas of constant barometric maxima of thunder-storms doesn't happen.
In Russia, on researches of the prof. A. V. Klossovsky ("Thunder-storms in Russia", 1884), storm activity is distributed as follows. In the Arkhangelsk and Olonets lips. the thunder-storm happens only 6-8 in a year. In Baltic lips. it is slightly more than them — about 10 at coast and 12-13 in some distance from the coast. To the East and the Southeast from here their number remains almost invariable, to the South increases, and in the Southwest of Russia reaches a maximum; here in a year happens to 20 thunder-storms. At coast of the Black Sea storm activity quickly falls; it is especially weak in the Crimea where in a year there are only about 6 thunder-storms. In the Urals the number of thunder-storms are more, than in Central and east Russia that depends on influence of mountains.
We meet strong increase in storm activity in the Caucasus. In the aralo-Caspian steppes of a thunder-storm are much less frequent, than somewhere in Europe, except the North. In a midland of Siberia, between 50 ° and 60 °, is to 15 thunder-storms a year. As the warm time of day is optimum for formation of the ascending air currents, thunder-storms in these times have to be most frequent. And it is valid, in the moderate countries of a thunder-storm of everything is more often in the summer and between 2 and 6 o'clock in the afternoon.
Night thunder-storms are most frequent in the south of Russia and in the Western region. As for before influence of seasons, in general summer — time of the most frequent thunder-storms as then conditions are favorable for the ascending currents of air and it is richer with couples. But where summer cool, and in winter there are very strong cyclones as on North Western Europe, thunder-storms are distributed more evenly, and in their Iceland even happens more in the winter, than in the summer. Then where clear and dry weather, and in the spring in the summer dominates and in the fall more often there are rains, thunder-storms are also more often in these seasons and are rare in the summer. Conditions of coast of the Mediterranean Sea, and in Russia — the southern coast of the Crimea and the plain восточн are that. Transcaucasia. Behind these exceptions in Russia summer thunder-storms resolutely prevail.
In northern and Central Russia thunder-storms most often in July, in the south — in June. Details of rather geographical distribution of thunder-storms, annual and their daily course see in compositions: H. Klein, "Das Gewitter und die dasselbe begleit. Erscheinungen" (1871); W. von Bezold, "Ueber das doppelte Maximum in der Haufigkeit der Gewitter" ("Sitzungsberichte der Munchen. Akad.", 1875); G. Hellmann, "Ueber die tagliche periode der Gewitter in Mittel Europa" ("Meteor. Zeitschr.", 1885), A. B. Klossovsky, "Thunder-storms in Russia" (1884); article A. M. Shenrok and E. Berg in "the Meteorologist. Collection", prod. Imp. act. sciences.
In 1865 according to Leverye in France the network of storm stations was for the first time organized. Norway (1867), Sweden and Russia (1871), Belgium and Italy (1876), Bavaria (1879), Wurtemberg (1880), Saxony followed the example of France (1880) soon. In Russia the correct supervision over thunder-storms began on an initiative Imp. Russian geographic general in 1871. Results for this year are printed by the prof. A. I. Voyeykov in "Notes Imp. Russian geographic general" in 1875; supervision for 1872-1882 are processed by the prof. A. V. Klossovsky and printed in his article "Thunder-storms in Russia", 1884. In 1884 the network of storm stations in Russia was organized by the main physical observatory. Supervision of this network are published in "Chronicles of the main physical observatory, and results in "the Meteor. collection", prod. Imp. act. sciences. 951 observation posts were a part it in 1891. In 1886 the prof. A. V. Klossovsky in Odessa laid the foundation of a special storm network and in the southwest of Russia.
Originally its activity was limited the Kherson province, but since the end of 1887 began to extend and on the neighboring provinces. In 1891 in it there were 378 stations. Results are printed annually in the "Works of a meteorological network of the southwest of Russia" published by the prof. A. V. Klossovsky. In 1887 the Finnish society of sciences organized a network of storm stations in Finland. It the prof. A. F. Zyondel manages; supervision are printed in "Askvadren i Finland" published by the specified society. At last, in 1892 meteorogichesky observatory унив. St. Vladimir in Kiev the foundation of the organization of the Dnieper storm network is laid. From all these networks the most frequent — fr. and Bavarian with vyurtembergsky. In the first now about 4000 stations, in the second — 529. Results of the first are printed in "Annales du Bureau Central Meteorologique de France" supplied by fine cards of thunder-storms, the second — in "Beobachtungen der meteorolog. Stationen in Konigreich Bayern". Also storm network Kherson lips is very frequent.
Supervision of storm networks led to many curious results in relation to thunder-storms of Europe from which we will specify the major. At research of thunder-storms, they are applied ordinary on meteorological charts (see also Storms). Betsold, the organizer of the Bavarian network, plotted the moments at which observers were audible the first and last thunder (the beginning and the end of a thunder-storm; "Beobachtungen der meteorolog. Stationen im Konigreiche Bayern", 1880). Through points with the simultaneous beginnings or the simultaneous ends of thunder-storms lines — izobronta were drawn.
The Italian meteorologist of Ferrari, meaning that time of approach of the greatest force of a thunder-storm is defined by observers more true, suggested to plot the moments of approach of a maximum of a thunder-storm or, something, the moments when the thunder-storm was in the next distance from a supervision place (Cirro Ferrari, "Osservazioni dei temporali raccolte nel 1880"). The lines corresponding to these moments received the name isochrone. Comparison изохрон with isobars (see atmosphere Pressure) shows that thunder-storms ordinary happen in private barometric minima, or the private cyclones (see Storms) which are formed in areas of ordinary (main) cyclones and together with them moving. Together with private cyclones also thunder-storms move.
Private cyclones, and together with them and thunder-storms, are most often formed in cyclones at their suburbs in a belt of 755 mm — 760 mm in southeast part them. In anti-cyclones (see atmosphere Pressure) thunder-storms don't happen. In Europe most often thunder-storms move about the SKID, Z and SZ, as well as it was necessary to assume on the basis of their communication with cyclones; the thunder-storms going since Century are most rare. The same belongs, of course, and to Russia, apparently from the following table showing how often there are thunder-storms from the different countries of light as a percentage:
Speed of distribution of a thunder-storm is depending on the speed of the movement of private minima: in Russia, on average a conclusion, it 38 km/h, in France 41, in Italy 34, in Bavaria 38, in Norway 38. It is more for the thunder-storms moving from the West, and less for the thunder-storms going from the East. Izokhrona in most cases represent themselves the curves close to straight lines. But sometimes thunder-storms move from an education place radially, in all directions; then izokhrona are close to circles of circles. The area occupied on a meteorological chart of an izokhronama of this thunder-storm carries the name of storm area. Width of storm area — some tens, length — some honeycombs of km. In storm area a narrow strip the hail strip (Cirro Ferrari, 1881, also "Meteor settles down ordinary. Zeitschr.", 1885).
On the table "Thunder-storms" (fig. I) continuous lines presented izokhrona of the thunder-storm which was in Russia on May 31, 1886. (A. Shenrok "To a question of research of thunder-storms in Russia", enc. to the LXI t. Zap. Imp. act. sciences).
Numbers, at them standing, show, in what hours the thunder-storm was in those places through which they pass. They are carried out in an hour. Dashed lines an isobar essence for 9 h. evenings on May 31. Shooters point to the general direction of a thunder-storm. The main minimum is in the north of Russia, and private — about Kostroma (an isobar of 752 mm). To the SKID of an isobar from it find a new private minimum. At that moment for which nacherchena of an isobar, thunder-storms were located on the line close to an axis of this minimum (an izokhron of 9 hours) . The first a thunder-storm appeared on May 31 at 1 o'clock in the afternoon in the Vitebsk province and in two places Novgorod and went three separate waves to YuV from here. At 3 o'clock p.m. all three waves connected in one and then all in the same direction, and, however, send a long line sowing. - east wave outstripped others two owing to what bends in the izokhronakh were formed. Just in these bends the strongest thunder-storms as it is visible on the table (fig. I) on which broken shooters designated places where there were lightning strokes were observed. After 9 h. thunder-storms stopped, except for a South zap. and sowing. - вост. fronts where they were observed to 12 h., even till one o'clock in the morning (letters and and р, standing on the drawing at numbers, mean: the first — time of 12 h. nights to 12 h. day, the second — other part of days; the triangle means a hail).
Also distribution of temperature in 9 h is specified the tab. evenings: the maximum of temperature is located before storm area, and the minimum lies behind it. To In from the southern part of a maximum of temperature one more private minimum (curved isobars) in which the new storm wave which went on Z to temperature maximum — the movement was at about noon formed is visible, to them, most likely, speaking. Thundersnows as very rare, are especially curious. One of those is described by E. Berg in "Prilozh. to the LXIII t. notes Imper. act. sciences". This thunder-storm was in the night of the 1st for December 2nd, 1887. It was formed in 6 h. 30 min. evening in Sweden to the East from Uppsala also I went from here to YuV, and then the South, having passed over average part of the Baltic Sea, Finland and Baltic lips. It stopped in Kovensky and Vilensky lips., having passed unusually considerable distance. Speed of its movement equaled 48 km/h.
Almost on all way it was followed by a storm, which with a special force of a svirpstvoval over the northernmost tip of the island of Dago and over the island Vormsom. The hurricane brought the sea, bichuyemy a hail and a rain, into extraordinary excitement, and the beacon (vormskiya) fluctuated even; on space of 8 versts round a beacon 1500 trees were broken. This thunder-storm was in a South vost. parts of a cyclone which center passed from зап. прибрежья Scandinavian to an island floor to sowing. to the end of the Gulf of Bothnia. The remarkable thundersnow is described also by the prof. A. V. Klossovsky ("Meteorologich. Messenger", 1892, February). It was formed in 1 h. day on January 15, 1892 in sowing. also I took place parts of the Crimean poluo-v on In to sowing. to the coast of the Sea of Azov.
This thunder-storm was formed in a South vost. parts of a private cyclone. Sometimes it happens that thunder-storms meet one another. Thus they are ordinary mutually destroyed that is explained by the air cooling followed a thunder-storm, interfering thunder-storm distribution. Such case is presented on the table "Thunder-storms" (the drawing of II). On it the thunder-storms which were in the southern Russia on June 5, 1886 are represented. (A. Shenrok, "To a question of research of thunder-storms in Russia", "Enc. to the LXI volume зап. Akkad. sciences"). In the morning this day in different places of the southern Russia thunder-storms which went in very various directions were formed, sometimes coinciding, being sometimes crossed by one with another. One of storm areas of this drawing represents itself area of radial distribution of a thunder-storm. (round izokhrona).
Passing to the essence of the storm phenomena, we will point to very important result to which send Asmann (Assmann, "Gewitter in Mitteldeutschland", 1885), Klossovsky ("Thunder-storms in Russia"), etc. It appears that the storm phenomena in this storm area consist of a number of the storm vikhrik moving progressively. Existence of these vikhrik is found detailed maps of isobars and winds, and also fast changes of the direction in wind force in that place about which there passes the thunder-storm. In ways of storm vikhrik, or so-called storm threads, it is possible to see repetition of difficult ways of cyclones in a miniature: there are both straight lines, and curves, both loops, and curls, and filched. Storm threads of one thunder-storm intertwine between themselves, segmented and merge, but generally move in the same direction, as well as air in a cyclone, seeking to be wrapped in the last.
Curious details about storm vikhrika are reported by S. Popruzhenko in the article "Storm Activity in the Southwest of Russia in 1890." ("Works" of a network of the southwest of Russia). From its researches the speed of distribution of vikhrik in southwest Russia turned out equal 39,7 to., i.e. approximately equal to the average speed of the movement of a thunder-storm in Russia, and the average radius of a storm whirlwind = 30,3 to. In compliance with it each izokhrona should be considered as the line connecting the separate vikhrik observed at the same moment. Storm activity happens, therefore, not on all izokhrena, but only in places. For formation of a thunder-storm of high temperature and big moisture it isn't enough: still existence of the ascending movement, at least and slow is necessary. These three conditions are most often satisfied in a South vost. parts of a cyclone at the suburb of the last where winds and the sky warm and rich with steam Yu, YuYuZ and YuYuV in places clearly blow, why here sunshine have a free access to a terrestrial surface.
Here the local heatings conducting for itself the local ascending currents in which top parts there is a plentiful sedimentation of vapors and formation of dense clouds are. Allocation of the hidden warmth supports the currents involving in themselves from below air and making thereof the vorticose movements and at the same time and falling of a barometer (a private minimum). The ascending currents are promoted by the fast decrease of temperature with height happening in a South vost. parts of cyclones that is proved theoretically and is confirmed by supervision on balloons (L. Sohnke, "Der Ursprung der Gewitterelectricitat" 1885). Currents are sometimes so strong that tornadoes (F. Erk, "by Eine Windhose zwischen Gewitterwolken, Beobacht are formed. der meteorol. Stationen in Bayern" 1892, also H. Hildebrandsson, "Les orages dans la peninsule Scandinave" — "Nova Acta Soc. Reg. Sc. Ups." 1888, also Th. Wigert, "Orage accompagne de trombes pres Upsala" — "Bihang till Kongl. Svenska Vet. Akad. Handl." Band 14, 1888). Storm tornadoes in sowing are especially remarkable. - the American. tornado (Finlay, "Report on the Character of Six Hundred Tornadoes" — "Professional Papers of the Signal Service" No. VII, Vashingt., 1882).
As the main reason of rainfall — the ascending currents of damp air, it is natural to expect close connection between them and thunder-storms that really and is confirmed (Klossovsky, "Thunder-storms in Russia").
Movement of thunder-storms depends mainly on the movement of the air in a cyclone which is carrying away the whirlwind formed in his environment. It, by the way, is proved to that the direction of the wind prevailing during a thunder-storm coincides with the direction of the movement of a thunder-storm (S. by Ferrari, "Sulla dinamica dei temporali"). It is caused also to a certain extent by temperature and humidity, and also local conditions. So, thunder-storms, meeting on the way cold districts (the rivers, lakes and so forth), bend around them, or jump through them, or, at last, absolutely stop; opposite to that, districts marshy, rich with water vapor, and sometimes strongly heating up, as if attract thunder-storms and in general promote development of storm activity. The same belongs and to the mountainous places representing favorable conditions for formation of the ascending currents.
Before a thunder-storm the atmospheric pressure and relative humidity decrease, temperature and absolute humidity increase. At the time of thunder-storm approach the first two reach a minimum, and the second — a maximum. After that pressure and relative humidity do jump up, and temperature — jump down. The reason of it consists in the rain making pressure upon the lower layers and at the same time their cooling. After a rain pressure becomes less, temperature starts increasing slowly. During a thunder-storm the curvature of isobars specified on the drawing very characteristic for thunder-storms, and in connection with it — the provision of a rain strip of R is explained by just specified changes of atmospheric pressure: one minimum of pressure, m, precedes a thunder-storm, another, weaker, n, follows it.
Wind force before a thunder-storm is ordinary small, at its beginning quickly increases and a maximum reaches at the end of a thunder-storm then quickly decreases. Owing to invasion from above of the air masses which are carried away by heavy rain and a hail during a thunder-storm there are quite often strong flaws (W. Koppen, "Gewitterboe" — "Annalen des Hydrographie", 1882, p. 595 and 714). A large amount of the water vapor escaping from craters of volcanoes during eruption serves as the reason remarkable by the force of volcanic thunder-storms.
When writing this text material was used from
Encyclopedic dictionary of Brockhaus F.A. and Efron I.A. (1890 — 1907).
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