The concept of an atmospheric front is commonly understood as a transition zone in which adjacent air masses meet. different characteristics. Fronts are formed when warm and cold air masses collide. They can stretch for tens of kilometers.

Air masses and atmospheric fronts

The circulation of the atmosphere occurs due to the formation of various air currents. Air masses located in the lower layers of the atmosphere are able to combine with each other. The reason for this is general properties these masses or identical origin.

Change weather conditions is due to movement air masses. Warm temperatures cause warming, and cold temperatures cause cooling.

There are several types of air masses. They are distinguished by the origin. Such masses are: arctic, polar, tropical and equatorial air masses.

Atmospheric fronts occur when various air masses collide. Collision areas are called frontal or transitional. These zones instantly appear and also quickly collapse - it all depends on the temperature of the colliding masses.

The wind generated by such a collision can reach speeds of 200 km/k at an altitude of 10 km from earth's surface. Cyclones and anticyclones are the result of collisions of air masses.

Warm and cold fronts

Warm fronts are fronts moving in the direction of cold air. The warm air mass moves along with them.

As warm fronts approach, pressure decreases, clouds thicken, and heavy precipitation falls. After the front has passed, the direction of the wind changes, its speed decreases, the pressure begins to gradually rise, and the precipitation stops.

A warm front is characterized by the flow of warm air masses onto cold ones, which causes them to cool.

It is also often accompanied by heavy rainfall and thunderstorms. But when there is not enough moisture in the air, precipitation does not fall.

Cold fronts are air masses that move and displace warm air. stand out cold front of the first kind and a cold front of the second kind.

The first genus is characterized by the slow penetration of its air masses under warm air. This process forms clouds both behind the front line and within it.

The upper part of the frontal surface consists of a uniform cover of stratus clouds. The duration of the formation and decay of a cold front is about 10 hours.

The second kind is cold fronts moving at high speed. Warm air is instantly displaced by cold air. This leads to the formation of a cumulonimbus region.

The first signals of the approach of such a front are high clouds, visually resembling lentils. Their education takes place long before his arrival. The cold front is located two hundred kilometers from the place where these clouds appeared.

Cold front of the 2nd kind in summer period accompanied by heavy precipitation in the form of rain, hail and squally winds. Such weather can spread for tens of kilometers.

In winter, a cold front of the 2nd kind causes a snow blizzard, strong winds, and turbulence.

Atmospheric fronts of Russia

The climate of Russia is mainly influenced by the Arctic Ocean, the Atlantic and the Pacific.

In summer, Antarctic air masses pass through Russia, affecting the climate of Ciscaucasia.

The entire territory of Russia is prone to cyclones. Most often they form over the Kara, Barents and Okhotsk Seas.

Most often in our country there are two fronts - the Arctic and the Polar. They move south or north during different climatic periods.

The southern part of the Far East is subject to the influence of the tropical front. Heavy rainfall for middle lane Russia are caused by the impact of the polar dandy, which operates in July.

atmospheric front, tropospheric fronts - a transition zone in the troposphere between adjacent air masses with different physical properties.

An atmospheric front occurs when masses of cold and warm air approach and meet in the lower layers of the atmosphere or in the entire troposphere, covering a layer up to several kilometers thick, with the formation of an inclined interface between them.

Types :

warm front - an atmospheric front moving towards colder air (heat advection is observed). Behind the warm front this region warm air comes in.

On the weather map, a warm front is marked in red or as black semicircles pointing in the direction of the front movement. As the warm front line approaches, pressure begins to drop, clouds thicken, and heavy precipitation falls. In winter, when the front passes, low stratus clouds usually appear. The temperature and humidity of the air are slowly rising. When a front passes, temperature and humidity usually increase rapidly, and the wind increases. After the passage of the front, the direction of the wind changes (the wind turns clockwise), the pressure drop stops and its weak growth begins, the clouds dissipate, and precipitation stops. The baric tendencies field is represented as follows: a closed area of ​​pressure drop is located in front of the warm front, and behind the front there is either an increase in pressure or a relative increase (a drop, but less than in front of the front).

In the case of a warm front, warm air, moving towards a cold front, flows into a wedge of cold air and performs an upward sliding along this wedge and is dynamically cooled. At a certain altitude, determined by the initial state of the rising air, saturation is reached - this is the level of condensation. Above this level, cloud formation occurs in the rising air. The adiabatic cooling of warm air sliding along the cold wedge is enhanced by the development of ascending motions from nonstationarity with a dynamic pressure drop and from wind convergence in the lower layer of the atmosphere. Cooling of warm air during upward sliding over the surface of the front leads to the formation characteristic system stratus clouds (ascending clouds): cirrostratus - altostratus -nimbostratus (Cs-As-Ns).

When approaching a point of a warm front with well-developed cloudiness, cirrus clouds first appear in the form of parallel bands with claw-like formations in the front (harbingers of a warm front), elongated in the direction of air currents at their level (Ci uncinus). The first cirrus clouds are observed at a distance of many hundreds of kilometers from the front line near the Earth's surface (about 800-900 km). Cirrus clouds then pass into cirrostratus clouds (Cirrostratus). These clouds are characterized by halo phenomena. Clouds of the upper tier - cirrostratus and cirrus (Ci and Cs) consist of ice crystals, and precipitation does not fall out of them. Most often, Ci-Cs clouds are an independent layer, the upper boundary of which coincides with the axis of the jet stream, that is, close to the tropopause.

Then the clouds become denser: altostratus clouds (Altostratus) gradually turn into nimbostratus clouds (Nimbostratus), heavy precipitation begins to fall, which weaken or completely stop after passing the front line. As we approach the front line, the base height Ns decreases. Its minimum value is determined by the height of the level of condensation in the rising warm air. Highly stratified (As) are colloidal and consist of a mixture of tiny droplets and snowflakes. Their vertical power is quite significant: starting at a height of 3-5 km, these clouds extend to heights of the order of 4-6 km, that is, they are 1-3 km thick. The precipitation falling from these clouds in the summer, passing through warm part atmosphere, evaporate and do not always reach the Earth's surface. In winter, precipitation from As in the form of snow almost always reaches the Earth's surface, and also stimulates precipitation from the underlying St-Sc. In this case, the wide precipitation zone can reach a width of 400 km or more. The closest to the Earth's surface (at a height of several hundred meters, and sometimes 100-150 m or even lower) is bottom line nimbostratus clouds (Ns) from which extensive precipitation falls in the form of rain or snow; nimbus clouds often develop under nimbus clouds (St fr).

Clouds Ns extend to heights of 3...7 km, that is, they have a very significant vertical power. The clouds also consist of ice elements and drops, and the drops and crystals, especially in the lower part of the clouds, are larger than in As. The lower base of the As-Ns cloud system in in general terms coincides with the surface of the front. Since the upper boundary of the As-Ns clouds is approximately horizontal, their greatest thickness is observed near the front line. Near the center of the cyclone, where the system of warm front clouds is most developed, the width of the cloud zone Ns and the zone of overt precipitation is on average about 300 km. In general, As-Ns clouds have a width of 500-600 km, the width of the Ci-Cs cloud zone is about 200-300 km. If projected this system on a surface map, then all of it will be in front of the warm front line at a distance of 700-900 km. In some cases, the zone of cloudiness and precipitation can be much wider or narrower, depending on the angle of inclination of the frontal surface, the height of the condensation level, and the thermal conditions of the lower troposphere.

At night, radiative cooling of the upper boundary of the As-Ns cloud system and a decrease in temperature in the clouds, as well as increased vertical mixing when the cooled air descends into the cloud, contribute to the formation of an ice phase in the clouds, the growth of cloud elements and the formation of precipitation. As you move away from the center of the cyclone, the ascending air movements weaken, and precipitation stops. Frontal clouds can form not only over inclined surface front, and in some cases - and on both sides of the front. This is especially true for initial stage cyclone, when ascending movements capture the frontal area - then precipitation can also fall on both sides of the front. But behind the front line, the frontal cloudiness is usually highly stratified, and behind the frontal precipitation is more often in the form of drizzle or snow grains.

In the case of a very flat front, the cloud system can be shifted forward from the front line. In the warm season, ascending movements near the front line become convective, and cumulonimbus clouds often develop on warm fronts and showers and thunderstorms are observed (both during the day and at night).

In summer, in the daytime, in the surface layer behind the warm front line, with significant cloud cover, the air temperature over land can be lower than ahead of the front. This phenomenon is called warm front masking.

The cloudiness of old warm fronts can also be stratified along the entire length of the front. Gradually, these layers dissipate and precipitation stops. Sometimes a warm front is not accompanied by precipitation (especially in summer). This happens when the moisture content of warm air is low, when the level of condensation lies at a considerable height. When the air is dry, and especially in the case of its noticeable stable stratification, the upward sliding of warm air does not lead to the development of more or less powerful clouds - that is, there are no clouds at all, or a band of clouds of the upper and middle tiers is observed.

cold front - an atmospheric front (a surface separating warm and cold air masses) moving towards warm air. Cold air advances and pushes warm air: cold advection is observed, a cold air mass comes to the region behind the cold front.

On the weather map, a cold front is marked in blue or as black triangles pointing in the direction of the front movement. When crossing the line of a cold front, the wind, as in the case of a warm front, turns to the right, but the turn is more significant and sharp - from the southwest, south (in front of the front) to the west, northwest (behind the front). This increases the wind speed. Atmospheric pressure ahead of the front changes slowly. It can fall, but it can also grow. With the passage of a cold front, a rapid increase in pressure begins. Behind the cold front, the pressure increase can reach 3–5 hPa/3 h, and sometimes 6–8 hPa/3 h or even more. A change in the pressure trend (from falling to rising, from slow to stronger growth) indicates the passage of a surface front line.

Before the front, precipitation is often observed, and often thunderstorms and squalls (especially in the warm half of the year). The air temperature after the passage of the front drops (cold advection), and sometimes quickly and sharply - by 5 ... 10 ° C or more in 1-2 hours. The dew point decreases along with the air temperature. Visibility tends to improve as cleaner, less humid air from northern latitudes invades behind the cold front.

The nature of the weather on a cold front differs markedly depending on the speed of the front displacement, the properties of warm air in front of the front, and the nature of the ascending motions of warm air above the cold wedge.

There are two types of cold fronts:

cold front of the first kind, when cold air advances slowly,

cold front of the second kind, accompanied by a rapid onset of cold air.

Front of occlusion - an atmospheric front associated with a heat ridge in the lower and middle troposphere, which causes large-scale ascending air movements and the formation of an extended zone of clouds and precipitation. Often, the occlusion front occurs due to closure - the process of displacing warm air upwards in the cyclone due to the fact that the cold front “catches up” with the warm front moving ahead and merges with it (the process of cyclone occlusion). Occlusion fronts are associated with intense precipitation, summer time- heavy showers and thunderstorms.

Due to downward movements in the cold air behind the cyclone, the cold front moves faster than the warm front and overtakes it over time. At the stage of cyclone filling, complex fronts arise - occlusion fronts, which are formed when cold and warm atmospheric fronts meet. In the occlusion front system, three air masses interact, of which the warm one no longer comes into contact with the Earth's surface. Warm air in the form of a funnel gradually rises up, and its place is taken by cold air coming from the sides. The interface that occurs when the cold and warm fronts meet is called the occlusion front surface. Intense precipitation is associated with occlusion fronts, and severe thunderstorms in summer.

Air masses closing during occlusion usually have different temperature- one may be colder than the other. In accordance with this, two types of occlusion fronts are distinguished - occlusion fronts of the warm front type and occlusion fronts of the cold front type.

In central Russia and the CIS, warm fronts of occlusion predominate in winter, since temperate sea air enters in the rear of the cyclone, which is much warmer than continental temperate air in front of the cyclone. In summer, cold fronts of occlusion are mainly observed here.

The baric field of the occlusion front is represented by a well-defined trough with V-shaped isobars. In front of the front on the synoptic map there is an area of ​​pressure drop associated with the surface of the warm front, behind the front of occlusion there is an area of ​​pressure increase associated with the surface of the cold front. The point on the synoptic map from which the remaining open sections of the warm and cold fronts in the occluding cyclone diverge is the point of occlusion. As the cyclone occludes, the occlusion point shifts to its periphery.

In the anterior part of the occlusion front, cirrus (Ci), cirrostratus (Cs), altostratus (As) clouds are observed, and in the case of active occlusion fronts, nimbostratus (Ns). If a cold front of the first kind is involved in the occlusion, then a part of the cold front cloud system may remain above the upper warm front. If a cold front of the second kind is involved, then a clearing occurs behind the upper warm front, but a shaft of cumulonimbus clouds (Cb) can develop near the lower cold front already in the front cold air, displaced by a colder rear wedge. Thus, precipitation from Altostratus and Doge Stratoclouds (As-Ns), if it occurs, may begin before the occurrence of showers, either simultaneously with or after the passage of a lower cold front; Precipitation can fall on both sides of the lower front, and the transition from heavy precipitation to showers, if it occurs, occurs not ahead of the lower front, but in close proximity to it.

The approaching cloud systems of warm and cold fronts mainly consist of As-Ns. As a result of the approach, a powerful Cs-As-Ns cloud system arises with the greatest thickness at the upper cold front. In the case of a young occlusion front, the cloud system starts with Ci and Cs, which change to As, then to Ns. Sometimes Ns can be followed by Cb, followed again by Ns. A weak upward sliding of the rear air along the occlusion surface can lead to the formation of stratus and stratocumulus (St-Sc) clouds along it, which do not reach the level of ice cores. Of these, drizzling precipitation will fall in front of the lower warm front. In the case of an old warm front of occlusion, the cloud system consists of cirrostratus (Cs) and altocumulus (Ac) clouds, sometimes joined by altostratus (As); rainfall may be absent.

Stationary front

1. A front that does not change its position in space.

2. A front along which air masses move horizontally; front without slips.

32) cyclones and anticyclones. Stages of their development, systems of winds and clouds in them.

Anticyclone- area of ​​increased atmospheric pressure with closed concentric isobars at sea level and with a corresponding wind distribution. In a low anticyclone - cold, the isobars remain closed only in the lowest layers of the troposphere (up to 1.5 km), and in the middle troposphere, increased pressure is not detected at all; the presence of a high-altitude cyclone above such an anticyclone is also possible.

Atmospheric fronts or simply fronts are transitional zones between two different air masses. The transition zone starts from the surface of the Earth and extends upward to the height where the differences between air masses are erased (usually to the upper limit of the troposphere). The width of the transition zone near the Earth's surface does not exceed 100 km.

In the transition zone - the zone of contact of air masses - there are drastic changes values ​​of meteorological parameters (temperature, humidity). Significant cloudiness is observed here, the most precipitation falls, the most intense changes in pressure, speed and wind direction occur.

Depending on the direction of movement of warm and cold air masses located on both sides of the transition zone, the fronts are divided into warm and cold. Fronts that change their position little are called inactive. A special position is occupied by occlusion fronts, which are formed when warm and cold fronts meet. Fronts of occlusion can be of the type of both cold and warm fronts. On weather maps, fronts are drawn either with colored lines or are given symbols(see Fig. 4). Each of these fronts will be discussed in more detail below.

2.8.1. warm front

If the front moves in such a way that cold air recedes, giving way to warm air, then such a front is called warm. Warm air, moving forward, not only occupies the space where cold air used to be, but also rises up along the transition zone. As it rises, it cools and the water vapor in it condenses. As a result, clouds are formed (Fig. 13).

Figure 13. Warm front on the vertical section and on the weather map.


The figure shows the most typical cloudiness, precipitation and air currents of a warm front. The first sign of a warm front approaching will be the appearance of cirrus clouds (Ci). The pressure will start to drop. After a few hours, cirrus clouds, condensing, pass into a veil of cirrostratus clouds (Cs). Following the cirrostratus clouds, even denser high-stratus clouds (As) flow in, gradually becoming opaque to the moon or the sun. At the same time, the pressure drops more strongly, and the wind, turning slightly to the left, intensifies. Precipitation can fall from altostratus clouds, especially in winter, when they do not have time to evaporate along the way.

After some time, these clouds turn into nimbostratus (Ns), under which there are usually nimbus clouds (Frob) and nimbus clouds (Frst). Precipitation from nimbostratus clouds falls more intensely, visibility deteriorates, pressure drops rapidly, wind increases, often takes on a gusty character. When crossing the front, the wind turns sharply to the right, the pressure drop stops or slows down. Precipitation may stop, but usually they only weaken and turn into drizzle. The temperature and humidity of the air gradually increase.

Difficulties that may be encountered when crossing a warm front are mainly associated with a long stay in a zone of poor visibility, the width of which varies from 150 to 200 NM. It is necessary to know that the conditions of navigation in temperate and northern latitudes when crossing a warm front in the cold half of the year worsen due to the expansion of the zone of poor visibility and possible icing.

2.8.2. cold front

A cold front is a front moving towards a warm air mass. There are two main types of cold fronts:

1) cold fronts of the first kind - slowly moving or slowing down fronts, which are most often observed on the periphery of cyclones or anticyclones;

2) cold fronts of the second kind - fast moving or moving with acceleration, they occur in the inner parts of cyclones and troughs moving at high speed.

Cold front of the first kind. A cold front of the first kind, as was said, is a slowly moving front. In this case, warm air slowly rises up the wedge of cold air that invades under it (Fig. 14).

As a result, nimbostratus clouds (Ns) are first formed over the interface zone, passing at some distance from the front line into highly stratus (As) and cirrostratus (Cs) clouds. Precipitation begins to fall at the very front line and continues after it has passed. The width of the frontal precipitation zone is 60-110 nm. IN warm time In the forward part of such a front, favorable conditions are created for the formation of powerful cumulonimbus clouds (Cb), from which showers fall, accompanied by thunderstorms.

The pressure just before the front drops sharply and a characteristic “thunderstorm nose” is formed on the barogram - a sharp peak facing downwards. The wind turns towards it just before the passage of the front, i.e. makes a left turn. After the front passes, the pressure begins to increase, the wind turns sharply to the right. If the front is located in a well-defined hollow, then the wind turn sometimes reaches 180 °; for example, a southerly wind can be replaced by a northerly one. With the passage of the front comes a cold snap.


Rice. 14. Cold front of the first kind on a vertical section and on a weather map.


Sailing conditions when crossing a cold front of the first kind will be affected by poor visibility in the precipitation zone and squally winds.

Cold front of the second kind. This is a fast moving front. The rapid movement of cold air leads to a very intense displacement of prefrontal warm air and, as a consequence, to a powerful development of cumulus clouds (Cu) (Fig. 15).

Cumulonimbus clouds on high altitudes usually stretch forward 60-70 NM from the front line. This front part of the cloud system is observed in the form of cirrostratus (Cs), cirrocumulus (Cc), as well as lenticular altocumulus (Ac) clouds.

The pressure in front of the approaching front drops, but weakly, the wind turns to the left, and heavy rain falls. After the passage of the front, the pressure increases rapidly, the wind turns sharply to the right and increases significantly - it takes on the character of a storm. The air temperature sometimes drops by 10 ° C in 1-2 hours.


Rice. 15. Cold front of the second kind on a vertical section and on a weather map.


Navigation conditions when crossing such a front are unfavorable, since near the front line powerful ascending air currents contribute to the formation of a vortex with destructive wind speeds. The width of such a zone can be up to 30 NM.

2.8.3. Sedentary, or stationary, fronts

The front, which does not experience a noticeable shift either towards the warm or towards the cold air mass, is called stationary. Stationary fronts are usually located in a saddle or in a deep trough, or on the periphery of an anticyclone. The cloud system of a stationary front is a system of cirrostratus, altostratus and nimbostratus clouds, which looks approximately like a warm front. In summer, cumulonimbus clouds often form at the front.

The direction of the wind on such a front hardly changes. The wind speed on the side of cold air is less (Fig. 16). The pressure does not change significantly. In a narrow band (30 NM) heavy rain falls.

Wave disturbances can form on the stationary front (Fig. 17). The waves quickly move along the stationary front in such a way that the cold air remains on the left - in the direction of the isobars, i.e. in a warm air mass. The speed of movement reaches 30 knots or more.


Rice. 16. Sedentary front on the weather map.



Rice. 17. Wave disturbances on a sedentary front.



Rice. 18. The formation of a cyclone on a sedentary front.


After the passage of the wave, the front restores its position. Strengthening of the wave disturbance before the formation of a cyclone is observed, as a rule, if cold air is leaking from the rear (Fig. 18).

In spring, autumn, and especially summer, the passage of waves on a stationary front causes the development of intense thunderstorm activity, accompanied by squalls.

Navigation conditions when crossing a stationary front are complicated due to the deterioration of visibility, and in summer, due to the wind strengthening to a storm.

2.8.4. Fronts of occlusion

Occlusion fronts are formed as a result of the merging of cold and warm fronts and the displacement of warm air upwards. The closure process occurs in cyclones, where a cold front, moving at high speed, overtakes a warm one.

Three air masses are involved in the formation of an occlusion front - two cold and one warm. If the cold air mass behind the cold front is warmer than the cold mass ahead of the front, then it, while displacing the warm air upwards, will simultaneously itself flow onto the front, colder mass. Such a front is called warm occlusion (Fig. 19).


Rice. 19. Front of warm occlusion on the vertical section and on the weather map.


If the air mass behind the cold front is colder than the air mass ahead of the warm front, then this rear mass will flow both under the warm and under the front cold air mass. Such a front is called cold occlusion (Fig. 20).

Occlusion fronts go through a number of stages in their development. The most difficult weather conditions on the fronts of occlusion are observed at the initial moment of closure of the thermal and cold fronts. During this period, the cloud system, as seen in Fig. 20 is a combination of warm and cold front clouds. Precipitation of a general nature begins to fall out of stratified-nimbus and cumulonimbus clouds, in the front zone they turn into showers.

The wind before the warm front of occlusion increases, after its passage it weakens and turns to the right.

Before the cold front of occlusion, the wind increases to a storm, after its passage it weakens and turns sharply to the right. As warm air is displaced into higher layers, the occlusion front gradually erodes, the vertical power of the cloud system decreases, and cloudless spaces appear. Nimbostratus cloudiness gradually turns into stratus, altostratus into altocumulus and cirrostratus into cirrocumulus. Rainfall stops. The passage of old fronts of occlusion is manifested in the flow of high-cumulus clouds of 7-10 points.


Rice. 20. Front of cold occlusion on a vertical section and on a weather map.


The conditions of navigation through the zone of the front of occlusion in the initial stage of development are almost the same as the conditions of navigation, respectively, when crossing the zone of warm or cold fronts.

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cold VM weather

Warm VM weather

A warm VM, moving to a cold region, becomes stable (cooling from the cold underlying surface). The air temperature, falling, can reach the level of condensation with the formation of haze, fog, low stratus clouds with precipitation in the form of drizzle or small snowflakes.

Flight conditions in a warm airframe in winter:

Light and moderate icing in clouds at low temperatures;

Clear sky, good visibility at H = 500-1000 m;

Weak chatter at H = 500-1000 m.

In the warm season, the conditions for flights are favorable, except for areas with separate centers of thunderstorms.

When moving to a warmer region, the cold VM heats up from below and becomes unstable VM. Powerful ascending air movements contribute to the formation of cumulonimbus clouds with heavy precipitation, thunderstorms.

atmospheric front- this is the section between two air masses that differ from one another in physical properties (temperature, pressure, density, humidity, cloudiness, precipitation, wind direction and speed). The fronts are located in two directions - horizontally and vertically.

The boundary between air masses along the horizon is called front line, the boundary between air masses along the vertical - called. frontal zone. The frontal zone is always inclined towards cold air. Depending on which VM comes - warm or cold, they distinguish warm TF and cold HF fronts.

characteristic feature fronts is the presence of the most dangerous (difficult) meteorological conditions for the flight. Frontal cloud systems are characterized by significant vertical and horizontal extent. Thunderstorms, turbulence, icing are observed on the fronts in the warm season, fogs, snowfall, and low clouds are observed in the cold season.

warm front is a front that moves in the direction of cold air, followed by warming.

A powerful cloud system is associated with the front, consisting of cirrostratus, altostratus, nimbostratus clouds, formed as a result of the rise of warm air along a cold wedge. SMU on the TF: low cloudiness (50-200m), fog ahead of the front, poor visibility in the precipitation zone, icing in the clouds and precipitation, ice on the ground.

The conditions of flight through the TF are determined by the height of the lower and upper boundaries of the clouds, the degree of stability of the VM, the temperature distribution in the cloud layer, moisture content, terrain, time of year, day.

1. If possible, stay in the zone of negative temperatures as little as possible;

2. Cross the front perpendicular to its location;


3. Choose a flight profile in the zone of positive temperatures, i.e. below the 0° isotherm, and if the temperature is below zero in the entire zone, the flight should be carried out where the temperature is below -10°. When flying from 0° to -10°, the most intense icing is observed.

When meeting with dangerous MU (thunderstorm, hail, heavy icing, heavy turbulence), you must return to the departure airfield or land at an alternate airfield.

- cold front - this is a section of the main front moving sideways high temperatures followed by a cold snap. There are two types of cold fronts:

-Cold front of the first kind (HF-1r)- this is a front moving at a speed of 20 - 30 km / h. Cold air, flowing like a wedge under warm air, displaces it upwards, forming cumulonimbus clouds, heavy rainfall, and thunderstorms ahead of the front. Part of the TV flows onto the HV wedge, forming layered clouds and extensive precipitation behind the front. Heavy turbulence ahead of the front, poor visibility behind the front. The conditions of flight through the HF -1p are similar to the conditions for crossing the TF.

At the intersection of HF -1r, one can meet a weak and moderate turbulence, where warm air is displaced by cold air. Flying at low altitudes can be hampered by low clouds and poor visibility in the rain zone.

Cold front of the second kind (HF - 2p) - This is a front moving fast at a speed = 30 - 70 km/h. Cold air quickly flows under warm air, displacing it vertically upwards, forming vertically developed cumulonimbus clouds in front of the front, heavy rainfall, thunderstorms, and squalls. It is forbidden to cross the KhF - the 2nd kind due to strong turbulence, a flurry of thunderstorm activity, a strong development of cloudiness along the vertical - 10 - 12 km. The width of the front near the ground is from tens to hundreds of kilometers. As the front passes, the pressure increases.

Under the influence of downward flows in the front, after its passage, a clearing occurs. Subsequently, the cold air, falling on the warm underlying surface, becomes unstable, forming cumulus, powerful cumulus, cumulonimbus clouds with showers, thunderstorms, squalls, strong turbulence, wind shear, and secondary fronts are formed.

Secondary fronts - These are fronts that form within the same VM and separate areas with warmer and colder air. The flight conditions in them are the same as on the main fronts, but weather phenomena are less pronounced than on the main fronts, but here you can also find low clouds, poor visibility due to precipitation (blizzards in winter). Thunderstorms, heavy rainfall, squalls, and wind shear are associated with secondary fronts.

Stationary fronts - these are fronts that remain motionless for some time, are located parallel to the isobars. The cloud system is similar to TF clouds, but with a small horizontal and vertical extent. Fog, ice, icing can occur in the front zone.

Upper fronts this is the state when the surface of the front does not reach the surface of the earth. This happens if a strongly cooled layer of air is encountered on the path of the front or the front is washed out in the surface layer, and difficult weather conditions (jet, turbulence) still persist at heights.

Fronts of occlusion formed as a result of the merging of cold and warm fronts. When the fronts close, their cloud systems close. The process of closure of TF and HF begins in the center of the cyclone, where HF, moving at a higher speed, overtakes the TF, gradually spreading to the periphery of the cyclone. Three VMs are involved in the formation of the front: - two cold and one warm. If the air behind the HF is less cold than before the TF, then when the fronts close, a complex front is formed, called WARM FRONT OCCLUSION.

If the air mass behind the front is colder than the front, then the rear part of the air will flow under the front, which is warmer. Such a complex front is called COLD FRONT OF OCCLUSION.

Weather conditions on occlusion fronts depend on the same factors as on the main fronts: - the degree of VM stability, moisture content, heights of the lower and upper cloud boundaries, terrain, season, day. At the same time, the weather conditions of cold occlusion in the warm season are similar to the weather conditions of the HF, and the weather conditions of warm occlusion in the cold season are similar to the weather of the TF. Under favorable conditions, occlusion fronts can turn into main fronts - warm occlusion in the TF, cold occlusion into a cold front. The fronts move along with the cyclone, turning counterclockwise.

The weather in our country is unstable. This is especially evident in the European part of Russia. This is due to the fact that different air masses meet: warm and cold. Air masses differ in properties: temperature, humidity, dust content, pressure. Atmospheric circulation allows air masses to move from one part to another. Where air masses of different properties come into contact, atmospheric fronts.

Atmospheric fronts are inclined to the Earth's surface, their width reaches from 500 to 900 km, and they extend for 2000-3000 km in length. In the frontal zones, there is an interface between two types of air: cold and warm. Such a surface is called frontal. As a rule, this surface is inclined towards cold air - it is located under it as a heavier one. And warm air, lighter, is located above the frontal surface (see fig. 1).

Rice. 1. Atmospheric fronts

The line of intersection of the frontal surface with the surface of the Earth forms front line, which is also briefly called front.

atmospheric front- transitional zone between two dissimilar air masses.

Warm air, being lighter, rises. Rising, it cools, saturated with water vapor. Clouds form and precipitation falls. Therefore, the passage of an atmospheric front is always accompanied by precipitation.

Depending on the direction of movement, moving atmospheric fronts are divided into warm and cold. warm front formed when warm air flows into cold air. The front line moves in the direction of cold air. After the passage of a warm front, warming occurs. The warm front forms a continuous band of clouds hundreds of kilometers long. There are long drizzling rains, and warming comes. The rise of air during the onset of a warm front occurs more slowly compared to a cold front. Cirrus and cirrostratus clouds forming high in the sky are a harbinger of an approaching warm front. (see Fig. 2).

Rice. 2. Warm atmospheric front ()

It is formed when cold air leaks under warm air, while the front line moves towards warm air, which is forced upward. As a rule, a cold front moves very quickly. It causes strong winds, heavy, often heavy rainfall with thunderstorms, and snowstorms in winter. After the passage of a cold front, a cold snap sets in. (See Fig. 3).

Rice. 3. Cold front ()

Atmospheric fronts are stationary and moving. If air currents do not move towards cold or towards warm air along the front line, such fronts are called stationary. If the air currents have a movement velocity perpendicular to the front line and move either towards cold or towards warm air, such atmospheric fronts are called moving. Atmospheric fronts arise, move and collapse in about a few days. The role of frontal activity in climate formation is more pronounced in temperate latitudes ah, so most of Russia is characterized by unstable weather. The most powerful fronts occur when the main types of air masses come into contact: arctic, temperate, tropical (see Fig. 4).

Rice. 4. Formation of atmospheric fronts in Russia

Zones reflecting their long-term positions are called climate fronts. On the border between arctic and temperate air, over the northern regions of Russia, a arctic front. Air masses of temperate latitudes and tropical ones are separated by a polar temperate front, which is located mainly to the south of the borders of Russia. The main climatic fronts do not form continuous strips of lines, but are broken into segments. Long-term observations have shown that the Arctic and Polar fronts are shifting southward in winter and northward in summer. In the east of the country, the Arctic front reaches the coast of the Sea of ​​Okhotsk in winter. To the northeast of it, very cold and dry arctic air dominates. In European Russia, the Arctic front does not move that far. This is where the warming effect of the North Atlantic Current comes into play. The branches of the polar climate front stretch over the southern territories of our country only in summer, in winter they lie over mediterranean sea and Iran and occasionally capture the Black Sea.

In the interaction of air masses take part cyclones And anticyclones- large moving atmospheric vortices carrying atmospheric masses.

An area of ​​low atmospheric pressure with a specific pattern of winds blowing from the edges towards the center and deviating counterclockwise.

An area of ​​high atmospheric pressure with a specific pattern of winds blowing from the center to the edges and deviating clockwise.

Cyclones are impressive in size, extend into the troposphere to a height of up to 10 km, and a width of up to 3000 km. Pressure increases in cyclones and decreases in anticyclones. In the northern hemisphere, the winds blowing towards the center of the cyclones are deflected by the force of the axial rotation of the earth to the right (the air spins counterclockwise), and in the central part the air rises. In anticyclones, the winds directed to the outskirts also deviate to the right (the air swirls clockwise), and in the central part the air descends from the upper layers of the atmosphere down (see fig. 5, fig. 6).

Rice. 5. Cyclone

Rice. 6. Anticyclone

The fronts on which cyclones and anticyclones originate are almost never rectilinear, they are characterized by wavy bends. (See Fig. 7).

Rice. 7. Atmospheric fronts (synoptic map)

In the formed bays of warm and cold air, rotating tops are formed atmospheric vortices (see fig. 8).

Rice. 8. Formation of an atmospheric vortex

Gradually, they separate from the front and begin to move and carry air on their own at a speed of 30-40 km / h.

Atmospheric vortices live for 5-10 days before destruction. And the intensity of their formation depends on the properties of the underlying surface (temperature, humidity). Several cyclones and anticyclones form daily in the troposphere. There are hundreds of them throughout the year. Every day our country is under the influence of some kind of atmospheric vortex. Since the air rises in cyclones, cloudy weather with precipitation and winds is always associated with their arrival, cool in summer and warm in winter. During the entire stay of the anticyclone, cloudless dry weather prevails, hot in summer And frosty in winter. This is facilitated by the slow sinking of air down from the higher layers of the troposphere. The descending air heats up and becomes less saturated with moisture. In anticyclones, the winds are weak, and in their inner parts there is complete calm - calm(see fig. 9).

Rice. 9. Air movement in an anticyclone

In Russia, cyclones and anticyclones are confined to the main climatic fronts: polar and arctic. They also form on the border between maritime and continental air masses of temperate latitudes. In the west of Russia, cyclones and anticyclones arise and move in the direction of the general air transport from west to east. In the Far East, in accordance with the direction of the monsoons. When moving with westward transfer in the east, cyclones deviate to the north, and anticyclones deviate to the south (see fig. 10). Therefore, the paths of cyclones in Russia most often pass through the northern regions of Russia, and anticyclones - through the southern ones. In this regard, the atmospheric pressure in the north of Russia is lower, there may be inclement weather for many days in a row, in the south there are more sunny days, dry summer and snowy winter.

Rice. 10. Deviation of cyclones and anticyclones when moving from the west

Areas where intense winter cyclones pass: the Barents, Kara, Okhotsk Seas and the northwest of the Russian Plain. In summer, cyclones are most frequent on Far East and in the west of the Russian Plain. Anticyclonic weather prevails throughout the year in the south of the Russian Plain, in the south of Western Siberia, and in winter over all of Eastern Siberia, where the Asian maximum pressure is established.

The movement and interaction of air masses, atmospheric fronts, cyclones and anticyclones change the weather and affect it. Data on weather changes are applied to special synoptic maps for further analysis of weather conditions on the territory of our country.

The movement of atmospheric vortices leads to a change in the weather. Her condition for each day is recorded on special maps - synoptic(see fig. 11).

Rice. 11. Synoptic map

Weather observations are carried out by an extensive network of meteorological stations. Then the results of the observations are transmitted to the centers of hydrometeorological data. Here they are processed, and weather information is applied to synoptic maps. The maps show atmospheric pressure, fronts, air temperature, wind direction and speed, cloudiness and precipitation. The distribution of atmospheric pressure indicates the position of cyclones and anticyclones. Having studied the patterns of flow atmospheric processes you can predict the weather. Accurate forecast weather is an extremely complex matter, since it is difficult to take into account the whole complex of interacting factors in their constant development. Therefore, even short-term forecasts of the hydrometeorological center are not always justified.

Source).).

  • Dust storm over the Arabian Sea ().
  • Cyclones and anticyclones ().

    • Homework

    1. Why does precipitation fall in the atmospheric front zone?
    2. What is the main difference between a cyclone and an anticyclone?