Thunderstorm is a natural phenomenon. Development, classification, thunderstorm activity

Thunderstorm - what is it? From where do the lightning cut through the whole sky and the thunderous peals of thunder? Thunderstorm is a natural phenomenon. Lightnings, called electric discharges, can form within the clouds (cumulonimbus), or between the earth's surface and the clouds. They are usually accompanied by thunder. Lightning is associated with heavy rains, heavy wind, and often with hail.

Activity

Thunderstorm is one of the most dangerous natural phenomena. People affected by lightning, survive only in isolated cases.

At the same time, there are approximately 1500 thunderstorms on the planet. The intensity of the discharges is estimated at a hundred lightnings per second.

The distribution of thunderstorms on the Earth is uneven. For example, over continents there are 10 times more of them than over the ocean. Most (78%) of lightning discharges are concentrated in the equatorial and tropical zones. Especially often there is a thunderstorm in Central Africa. But the polar regions (Antarctica, the Arctic) and poles of lightning practically do not see. The intensity of the thunderstorm turns out to be connected with the heavenly body. In the middle latitudes, its peak falls on the afternoon (daytime) hours, for the summer. But the minimum is registered before sunrise. Important and geographical features. The most powerful storm centers are in the Cordilleras and the Himalayas (mountainous areas). The annual number of "thunderstorm days" is also different in Russia. In Murmansk, for example, there are only four of them, for example, there are only four in Murmansk, fifteen in Arkhangelsk, eighteen in Kaliningrad, 16 in Petersburg, 24 in Moscow, 28 in Bryansk, 26 in Voronezh, 31 in Rostov, Sochi in 50, Samara in Samara, Ekaterinburg - 28, Ufa - 31, Novosibirsk - 20, Barnaul - 32, Chita - 27, Irkutsk and Yakutsk - 12, Blagoveshchensk - 28, Vladivostok - 13, Khabarovsk - 25, Yuzhno-Sakhalinsk - 7, Petropavlovsk-Kamchatsky - 1.

Thunderstorm development

How does it go? A cloud of cloud is formed only under certain conditions. It is necessary to have an upward flow of moisture, while there must be a structure where one part of the particles is in an ice state, the other in a liquid state. Convection, which will lead to the development of thunderstorms, will arise in several cases.

1. Uneven heating of surface layers. For example, over water with a significant temperature difference. Over large cities, the thunderous intensity will be somewhat stronger than in the vicinity.

2. When cold air is replaced by warm air. Frontal convention often develops simultaneously with complex and layered-rain clouds (clouds).

3. When air rises in mountain ranges. Even small elevations can lead to an increase in the formation of clouds. This is forced convection.

Any storm cloud, regardless of its type, necessarily passes through three stages: cumulus, maturity, the stage of decay.

Classification

Thunderstorms were classified for a time only at the place of observation. They were divided, for example, into orthographic, local, frontal. Now thunderstorms are classified according to characteristics that depend on those meteorological environments in which they develop. Ascending streams are formed because of the instability of the atmosphere. To create thunderclouds, this is the basic condition. The characteristics of such flows are very important. Depending on their power and magnitude, various types of thunderclouds are formed, respectively. How are they subdivided?

1. Cumulonimbus monocots, (local or intramuscular). Have a gradual or stormy activity. Transverse sizes from 5 to 20 km, vertical - from 8 to 12 km. Such cloud lasts up to an hour. After a thunderstorm the weather practically does not change.

2. Multicell cluster. Here the scale is more impressive - up to 1000 km. A multicell cluster covers a group of thunderstorm cells that are at different stages of formation and development and at the same time are a single whole. How are they arranged? Mature thunderous cells are located in the center, decaying - on the leeward side. Their transverse dimensions can reach 40 km. Cluster multicell storms "give" gusts of wind (squall, but not strong), downpour, hail. The existence of one mature cell is limited to half an hour, but the cluster itself can "live" for several hours.

3. Squall lines. This is also a multi-cell thunderstorm. They are also called linear. They can be either solid or with gaps. Gusts of wind are more prolonged (on the front line). The multicell line at approach seems like a dark wall of clouds. The number of flows (both ascending and descending) is quite large here. That is why such a complex of thunderstorms is classified as multicellular, although the thunderstorm structure is different. The squall line is capable of giving an intense downpour and a large hail, but more often it is "restricted" by strong descending flows. Often it passes before the cold front. In the pictures such a system has the shape of a curved bow.

4. Supercell storms. There are such thunderstorms rarely. They are especially dangerous for property and human life. The cloud of this system is similar to the one-cell system, since both are characterized by the same upflow zone. But they have different sizes. Super-cloud cloud - huge - close to 50 km in radius, height - up to 15 km. Its boundaries can be in the stratosphere. The shape resembles a single semicircular anvil. The rate of ascending currents is much higher (up to 60 m / s). A characteristic feature is the presence of rotation. It creates dangerous, extreme phenomena (large hail (more than 5 cm), destructive tornadoes). The main factor for the formation of such a cloud are the surrounding conditions. This is a very strong convention with a temperature of +27 and a wind with a variable direction. Such conditions arise when wind shears in the troposphere. Formed in ascending currents, the precipitation is transferred to the descending zone, which ensures a long life to the cloud. Precipitation is distributed unevenly. Downpours go near the ascending current, and hail - closer to the northeast. The back of the thunderstorm can shift. Then the most dangerous zone will be next to the main ascending current.

There is also the concept of "dry thunderstorm". This phenomenon is quite rare, typical for monsoons. With such a thunderstorm there are no precipitations (simply do not reach, evaporating as a result of exposure to high temperatures).

Movement speed

In an isolated thunderstorm, it is about 20 km / h, sometimes faster. If the cold fronts are active, the speed can be 80 km / h. In many thunderstorms, old thunderstorm cells are replaced with new ones. Each of them passes a relatively small path (about two kilometers), but in the aggregate the distance increases.

The mechanism of electrification

Where do the lightning come from? Electric charges around the clouds and inside them are constantly moving. This process is rather complicated. The easiest way to visualize the work of electric charges in mature clouds. The dipole positive structure dominates in them. How is it distributed? A positive charge is placed at the top, and a negative charge is placed beneath it, inside the cloud. According to the main hypothesis (this area of science can still be considered little-known), heavier and larger particles are charged negatively, and small and light particles have a positive charge. The first fall faster than the second. This causes the spatial separation of space charges. Such a mechanism is confirmed by laboratory experiments. Possess a strong transfer of charge may particles of ice grits or hail. The magnitude and sign will depend on the water content of the cloud, air temperature (ambient), collision velocity (main factors). Other mechanisms are not excluded. Discharges occur between the earth and the cloud (or neutral atmosphere, or ionosphere). It is at this moment that we observe flashing skies. Or lightning. This process is accompanied by loud rumblings (thunder).

Thunderstorm is a complex process. It can take many decades to study, and perhaps even centuries.