What is a cyclone? Almost every person is interested in the weather - looks at forecasts, reports. At the same time, he often hears about cyclones and anticyclones. Most people know that these atmospheric phenomena are directly related to the weather outside the window. In this article we will try to figure out what they are.
What is a cyclone
A cyclone is a low pressure zone covered by a system of circular winds. Simply put, it is a grandiose flat atmospheric vortex. Moreover, the air in it moves in a spiral around the epicenter, gradually approaching it. The reason for this phenomenon is considered to be low pressure in the central part. Therefore, warm moist air masses rush upward, rotating around the center of the cyclone (the eye). This causes the accumulation of high density clouds. Strong winds rage in this zone, the speed of which can reach 270 km / h. In the Northern Hemisphere, air rotates counterclockwise withsome twist towards the center. In anticyclones, on the contrary, the air swirls clockwise. A tropical cyclone in the Southern Hemisphere works much the same way. However, the directions are reversed. Cyclones can reach different sizes. Their diameter can be very large - up to several thousand kilometers. For example, a large cyclone is able to cover the entire European continent. As a rule, these atmospheric phenomena are formed in certain geographical points. For example, the southern cyclone comes to Europe from the Balkans; areas of the Mediterranean, Black and Caspian Seas.
Cyclone formation mechanism – first phase
What is a cyclone and how does it form? On the fronts, that is, in the zones of contact between warm and cold air masses, cyclones arise and develop. This natural phenomenon is formed when a mass of cold polar air meets a mass of warm, moist air. At the same time, warm air masses burst into an array of cold ones, forming something like a tongue in them. This is the beginning of the cyclone. Sliding relative to each other, these flows with different temperatures and air densities create a wave on the frontal surface, and, consequently, on the front line itself. It turns out a formation resembling an arc, turned by concavity towards warm air masses. Its segment, located in the front eastern part of the cyclone, is a warm front. The western part, which is located behind the atmospheric phenomenon, is a cold front. ATIn the interval between them in the cyclone, there are often zones of good weather, which usually lasts only a few hours. Such a deflection of the front line is accompanied by a decrease in pressure at the top of the wave.
Cyclone evolution: second phase
Atmospheric cyclone continues to evolve further. The formed wave, moving, as a rule, to the east, northeast or southeast, is gradually deformed. The tongue of warm air penetrates further to the north, forming a well-defined warm sector of the cyclone. In its front part, warm air masses float on colder and denser ones. As it rises, steam condenses and forms a powerful cumulonimbus cloud, which leads to precipitation (rain or snow) that lasts a long time. The width of the zone of such frontal precipitation is about 300 km in summer and 400 km in winter. At a distance of several hundred kilometers ahead of the warm front near the earth's surface, the ascending air flow reaches a height of 10 km or more, at which moisture condenses to form ice crystals. They form white cirrus clouds. Therefore, it is precisely from them that one can predict the approach of a warm front of a cyclone.
The third phase of the formation of an atmospheric phenomenon
Further characteristics of the cyclone. Humid warm air of the warm sector, passing over the colder surface of the Earth, forms low stratus clouds, fogs, and drizzle. After the passage of a warm front, warm cloudy weather with southerly winds sets in. Signs of this are often the appearance of haze and light fog. Then a cold front approaches. Cold air, passing along it, swims under warm air and displaces it upward. This leads to the formation of cumulonimbus clouds. They are the cause of showers, thunderstorms, which are accompanied by strong winds. The cold front precipitation zone is about 70 km wide. Over time, the back of the cyclone comes to replace. It brings strong winds, cumulus clouds and cool weather. Over time, cold air pushes warm air to the east. After that, clear weather sets in.
How Cyclones Form: Phase Four
As the tongue of warm air penetrates into the mass of cool air, it becomes more and more surrounded by cold air masses, and itself is forced upwards. This creates a zone of low pressure in the center of the cyclone, where the surrounding air masses rush. In the Northern Hemisphere, under the influence of the rotation of the Earth, they turn counterclockwise. As mentioned above, southern cyclones have opposite directions of rotation of air masses. It is precisely due to the fact that the Earth turns around its axis that the winds are not directed towards the center of the atmospheric phenomenon, but go tangentially to the circle around it. As the cyclone develops, they intensify.
The fifth phase of cyclone evolution
Cool air in the atmospheric phenomenon moves at a higher speed than warm air. Therefore, the cold front of the cyclone gradually merges with the warm one, forming the so-called occlusion front. AtThe surface of the Earth is no longer a warm zone. Only cold air masses remain there.
Warm air rises, where it gradually cools and is released from moisture reserves that fall to the ground in the form of rain or snow. The difference between the temperature of cold and warm air is gradually leveled. At the same time, the cyclone begins to fade. However, there is no complete homogeneity in these air masses. Following this cyclone, a second one appears near the front on the crest of a new wave. These atmospheric phenomena always come in series, with each following somewhat south of the previous one. The height of the cyclone vortex often reaches the stratosphere, that is, it rises to a height of 9-12 km. Especially large ones can be found at altitudes of 20-25 km.
Cyclone speed
Cyclones are almost always on the move. Their speed of movement can be very different. However, it decreases as the atmospheric phenomenon ages. Most often they move at a speed of about 30-40 km / h, covering a distance of 1000-1500 km or more in 24 hours. Sometimes they move at a speed of 70-80 km per hour and even more, passing 1800-2000 km per day. At this rate, the cyclone that raged today in the region of England, in 24 hours may already be in the region of Leningrad or Belarus, provoking a sharp change in the weather. As the center of the atmospheric phenomenon approaches, the pressure drops. There are various names for cyclones and hurricanes. One of the most famous is Katrina, which caused serious damage to the United States.
Atmospheric fronts
What iscyclones, we have already figured it out. Next, we will talk about their structural components - atmospheric fronts. What causes the huge masses of moist air in a cyclone to rise high up? To get an answer to this question, we first need to understand what the so-called atmospheric fronts are. We have already said that warm tropical air moves from the equator to the poles and on its way meets cold air masses of temperate latitudes. Since the properties of warm and cool air differ sharply, it is natural that their arrays cannot immediately mix. At the meeting point of air masses of different temperatures, a clearly defined band appears - a transition zone between air fronts with different physical properties, which in meteorology is called the frontal surface. The zone separating the air masses of temperate and tropical latitudes is called the polar front. And the frontal surface between temperate and arctic latitudes is called arctic. Since the density of warm air masses is less than that of cold ones, the front is an inclined plane, which always inclines towards the cold massif at an extremely small angle to the surface. Cool air, as denser, when meeting with warm air, raises the latter up. When imagining a front between air masses, one must always keep in mind that this is an imaginary surface tilted above the ground. The line of the atmospheric front, which is formed when this surface crosses the earth, is marked on weather maps.
Typhoon
I wonder if there is anything more beautiful in nature than such a phenomenon as a typhoon? A clear calm sky over a well of walls created by a crazy whirlwind, pierced by zigzags of lightning, walls two Everests high? However, big trouble threatens anyone who ends up at the bottom of this well…
Starting at equatorial latitudes, typhoons head west and then (in the Northern Hemisphere) turn northwest, north or northeast. Although each of them does not exactly follow the path of the other, most of them follow a curve that has the shape of a parabola. The speed of typhoons increases as they move northward. If near the equator and towards the west they move at a speed of only 17-20 km / h, then after turning to the northeast their speed can reach 100 km / h. However, there are times when, unexpectedly deceiving all forecasts and calculations, typhoons either stop completely or rush forward insanely.
Eye of the Hurricane
The eye is a bowl with convex walls of clouds, in which there is a relatively weak wind or complete calm. The sky is clear or partly cloudy. The pressure is 0.9 of the normal value. The eye of a typhoon can range in size from 5 to 200 km in diameter, depending on the stage of its development. In a young hurricane, the size of the eye is 35-55 km, while in a developed one it decreases to 18-30 km. As the typhoon fades, the eye grows again. The more clearly it is outlined, the more powerful the typhoon. In such hurricanes, the winds are stronger near the center. Closing all streams around the eye, the winds whirlat speeds up to 425 km/h, gradually slowing down as you move away from the center.
