Types of air masses and their characteristics. Air masses

Answering the question of what an air mass is, we can say that it is the human habitat. We breathe it, see it, feel it every day. Without the surrounding air, humanity would not be able to conduct its life activities.

The role of flows in the natural cycle

What is an air mass? This is the bringer of change weather conditions. Due to natural movement environment, precipitation moves thousands of kilometers along to the globe. Snow and rain, cold and warmth come according to established patterns. Scientists can predict climate change by delving deeper into the patterns of natural disasters.

Let's try to answer the question: what is air mass? Its striking examples include cyclones that move continuously. With them comes warming or cooling. They move with a constant pattern, but in in rare cases they deviate from the normal trajectory. As a result of such disturbances, disasters are discovered in nature.

So, in the desert snow falls from encountering cyclones different temperatures or tornadoes and hurricanes are formed. This all relates to the answer to the question: what is an air mass? Its condition determines what the weather will be like, the saturation of the air with oxygen or moisture.

Change of heat and cold: reasons

Air masses is the main participant in the formation of climate on earth. Heating of the layers of the atmosphere occurs due to the energy received from the sun. Due to temperature changes, air density changes. More sparse areas are filled with dense volumes.

Air masses are a collection of various conditions gaseous layers of the atmosphere, depending on the redistribution of heat due to the change of day and night. At night, the air cools, and wind appears, moving from denser layers to rarefied ones. The strength of the flow depends on the rate of temperature decrease, terrain, and humidity.

The movement of masses is affected by both horizontal and vertical temperature differences. During the day, the earth receives heat from the sun, beginning to release it to the lower layers of the atmosphere in the evening. This process continues all night, and the next morning water vapor is concentrated in the air. This causes precipitation: dew, rain, fog.

What are the different gaseous states?

The characteristics of air masses are a quantitative value with which one can describe certain states of gaseous layers and evaluate them.

There are three main indicators of the layers of the troposphere:

• Temperature provides information about the origin of mass displacement.
• Humidity is high in places located near seas, lakes and rivers.
• Transparency is defined externally. This parameter is affected by solid dust particles suspended in the air.

Highlight the following types air masses:

• Tropical - move to the side temperate latitudes.
• Arctic - cold masses, moving towards warm latitudes from the northern part of the planet.
• Antarctic - cold, moving from the south pole.
• Moderate, on the contrary, are warm air masses and move towards the cold poles.
• Equatorial regions are the warmest and disperse into areas with lower temperatures.

Subtypes

When air masses move, they transform from one geographical type to another. There are subtypes: continental, maritime. Accordingly, the former predominate on the land side, the latter bring moisture from the vast seas and oceans. There is a pattern of temperature differences in such masses depending on the season: in the summer the winds from the land are much warmer, and in the winter they warm the sea.

Everywhere there are dominant air masses that constantly prevail due to established patterns. They determine the weather in a given area, and, as a result, this leads to differences in vegetation and animal life. IN Lately The transformation of air masses has changed significantly due to human activity.

The transformation of air masses manifests itself more clearly on the coasts, where currents from land and sea meet. In some areas the wind does not subside even for a second. More often it is dry and does not change direction for a long time.

How does flow transformation occur in nature?

Air masses become visible under certain conditions. Examples of such phenomena are clouds, clouds, fogs. They can be located both at an altitude of thousands of kilometers and directly above the ground. The latter are formed when the ambient temperature sharply decreases due to high humidity.

The sun is playing important role in the endless process of movement of air masses. The change of day and night causes the streams to rush upward, lifting particles of water with them. High in the sky they crystallize and begin to fall. IN summer season When it is warm enough, the ice has time to melt in flight, so precipitation is observed mainly in the form of rain.

And in winter, when cold streams pass over the ground, snow or even hail begins to fall. Therefore, in the equatorial and tropical latitudes warm air straightens the crystals. In the regions northern regions This precipitation occurs almost every day. Cold streams are heated by heated earth's surface, the sun's rays pass through the air layers. But the heat given off at night causes the formation of clouds, morning dew, and fog.

How do you recognize a change in weather based on certain signs?

Even in the past, they learned to predict precipitation based on obvious signs:

• In the distance, white or ray-shaped areas become barely visible.
• A sharp increase in wind indicates the approach of cold masses. It may rain or snow.
• Clouds always gather in areas low pressure. Exists the right way define this area. To do this, you need to turn your back to the stream and look a little to the left of the horizon. If condensations appear there, then this is a clear sign of inclement weather. Don't be confused: clouds on the right side are not a sign of worsening weather conditions.
• The appearance of a whitish veil when the sun begins to fog.

The wind subsides as the cold area passes. Warmer currents fill the resulting vacuum, and it often becomes stuffy after rain.

Air masses

Definition 1

Air mass– a large volume of air in the moving part of the troposphere, which has its own homogeneous properties.

Some air masses are continental, others are maritime.

Definition 2

ocean, are called marine and are more humid.

Definition 3

Air masses formed over by land, are called continental and are drier.

Different places on the planet form their own air masses:

1. IN equatorial latitudes– equatorial air masses are formed;
2. In tropical latitudes - tropical;
3. In temperate latitudes there are moderate air masses;
4. In polar latitudes there are Arctic and Antarctic air masses.

Each air mass acquires the properties of the territory over which it was formed. The properties persist for a long time, therefore, when air masses move, their properties will determine the weather of the places where they arrive. Experts distinguish between stable and unstable air masses.

Over the continents sustainable air mass is most often observed in winter time. In a stable air mass, stable vertical equilibrium predominates. It is characterized by stratus and stratocumulus clouds with a base below $300$ m, having a small vertical thickness - usually $200$-$600$ m. The second characteristic feature for it is a slight change in temperature with height in the lower layers of the atmosphere, a smooth wind without gusts, small difference between air temperature and dew point. Turbulence in bottom layer There is no stable air mass, so dust particles can accumulate. In this case, with low humidity it may be clear weather with reduced visibility.

These weather conditions in cold weather years are typical for warm resistant air mass as it moves. It moves from a fairly warm ocean to a cold continent, or from a warm area of ​​the mainland to a colder area. A warm air mass becomes stable as it moves onto a cold surface, cooling from below.

Over the continents in winter it is observed cold resistant air mass. It is not observed over seas and oceans. Frosty, cloudless weather is typical.

Unstable the air mass is characterized by unstable stratification of the atmosphere in its lower layers. With sufficient humidity in an unstable air mass, convection develops with the formation of vertical clouds, increased turbulence, strong gusty winds, showers, thunderstorms, and squalls are noted. As its instability increases, it can rise to greater heights. Warm unstable air mass is observed in summer over continents and near sea coasts. It can also be observed in winter. IN cold half of the year it can be above the oceans and seas. Experts identify various conditions for its instability. Cloud cover is usually cumulus, sometimes cumulonimbus with showers and fog. Cold unstable air mass in summer period observed over continents, and in the cold season - over oceans and seas. It is observed in the rear parts of cyclones behind cold fronts. Associated with this air mass are cumulonimbus, cumulonimbus clouds, recurring showers, thunderstorms, and fogs. A special manifestation of cold unstable air mass is observed in April, when northern zone there is still snow, and the soil southern zone already warmed up.

Formation of air masses

Arctic air mass is formed in the polar region of the planet. In winter, its formation also occurs above northern parts Taimyr, Kolyma, Chukotka, Arctic America. In summer, Arctic air reaches the Sea of ​​Okhotsk through the Laptev Sea and the Kolyma basin. At the same time, there is no cooling, because the summer sea air over the Sea of ​​​​Okhotsk is colder than the Arctic air. Cold snap causes arctic air over the Bering Sea because it intrudes directly from the North Arctic Ocean. Then it gradually transforms into sea temperate air. The Arctic air mass, formed over frozen surfaces, is mainly continental. Passing over the continent in winter, the Arctic air cools even more, because a powerful Siberian anticyclone lies in its path. The continental air of this anticyclone is much colder. It turns out that in winter, cold advection comes not from the Arctic, but from the western continental regions.

Compared to the polar regions, moderate air masses, lower winter temperatures not only at the surface of the earth, but also in the thickness of the troposphere. To the seas Far East continental temperate air arrives in winter - the winter monsoon. This air is formed in the area of ​​the Siberian anticyclone - these are Mongolia, China, Transbaikalia, Yakutia, Lena-Kolyma region, Upper Amur. Continental temperate air, which is formed directly in the central part of the Siberian anticyclone, has very low temperatures. Moving southeast, it causes strong northwest winds and a sharp drop in air temperature. Continental temperate air is humidified and warmed over warm Sea of ​​Japan and may lead to heavy rainfall. Continental temperate air, which is formed on the periphery of the Siberian anticyclone, has a higher temperature - these are Mongolia and China. Invading the Sea of ​​Japan, it becomes humid and transforms into marine temperate air. Marine and continental air masses differ in humidity, the former have high humidity, and the latter are dry. The temperature of these air masses varies by season. In winter, the temperature of marine temperate air masses is higher, in summer it is the opposite.

In temperate latitudes most often tropical air comes from subtropical rather than tropical latitudes. In summer, it can form even in the south temperate zone. Tropical air develops over central China and Mongolia. Its distinctive feature is dryness, heat and low transparency. The source of formation of tropical sea air is the region of the Pacific subtropical anticyclone, and in the west the Mediterranean region.

Note 1

Air masses are formed within $3$-$10$ days. Their properties will depend on the time of formation; the longer this time, the more clearly the properties are expressed. As air masses move, they change their properties - they can become moistened, dried, cooled, or heated.

Physical properties of air masses

The air of the troposphere is not homogeneous in its physical properties. The heterogeneity of air properties is associated with uneven distribution solar energy and the influence of the underlying surface.

The physical properties of air include:

1. Air temperature;
2. Air humidity;
3. Air mobility;
4. Barometric air pressure;
5. Electrical state of air;
6. Air inertia;
7. Air viscosity;
8. Compressibility of air.

All these physical properties of air, one way or another, have an impact on humans.

For example, temperature air is a constantly acting environmental factor. Both high and low air temperatures affect the functional state of the central nervous system person.

Humidity air affects the body's heat exchange with environment, therefore has great importance. At low temperatures, the air contains a small amount of water vapor.

Heat loss from the body is associated with mobility air. This happens through convection and evaporation of sweat. If the temperature is high and air mobility is moderate, this will help cool the skin. Very coldy without wind they are much easier to carry. Increased air mobility affects metabolic processes.

Air has mass and weight, i.e. has a certain pressure, affecting the human body. Thanks to gravitational field air masses near the surface are the densest. Air pressure decreases with altitude, and its density also decreases.

The Earth's electric field is one of the elements electrical state air. According to the seasons, the electric field strength
air is different, in winter it is higher in the middle latitudes. Its value is influenced by the weather. High pressure and fogs increase the electric field of the atmosphere by $2$-$5$ times.

Air has the property of resisting changes in its state of rest - this is its inertia. The measure of inertia is the mass density of air. The larger it is, the greater the force must be that can remove the air from its state of rest.

Air can resist the mutual displacement of particles - this is its viscosity. Its molecules have a certain speed of random chaotic movement. It depends on the air temperature and general forward motion. If air molecules enter a slow layer from a fast-moving layer, they accelerate their movement and vice versa.

Compressibility air is its property in which it can change its density if the pressure changes.

Air mass (VM) is a volume of air that is relatively homogeneous in its basic physical and meteorological properties and retains its individuality for more or less a long time. The air mass spreads over several thousand kilometers in the horizontal direction and several kilometers in the vertical direction. It is formed under the condition of a long stay of air over an area with approximately uniform physical and geographical conditions. As air masses move, they transfer their characteristic properties to different regions of the Earth.

Thermal classification VM.

cold air masses - colder than the surrounding air and/or underlying surface. Moving to a warmer surface (usually from high to low latitudes), they bring.

cold snap warm air masses - warmer than the surrounding air and/or underlying surface..

Moving to a colder surface (to higher latitudes), they bring warming

local air masses

- are in thermal equilibrium with the environment. geographical classification air masses are divided depending on the geographical location of the formation centers. Highlight:

Arctic air is divided into sea and continental;

air of temperate latitudes, divided into sea and continental;

tropical air, divided into sea and continental;

equatorial air, Not is divided into maritime and continental, since in the region of the equator the temperature and humidity of the air over land and over the sea differ little.

Continental air is drier, sea air is more humid.

Atmospheric fronts

Adjacent air masses, differing from each other in their physical properties, are separated from each other by relatively narrow transitional, i.e.frontal zones (width – up to several tens of kilometers) . Main distinguishing feature frontal zone -sudden change meteorological characteristics in the horizontal direction, i.e. large horizontal gradients these characteristics.

Intersection line frontal zone with the surface of the earth - atmospheric front .Length the front lines correspond to the horizontal dimensions of the frontal zone and can reach 5 thousand km and more. Upward, most atmospheric fronts extend to altitude no more5-6 km. (Let's look at this using a simple example. The air in the classroom is one mini-mass, outside is another: they differ from each other in temperature, humidity, air composition. The outer wall is the “frontal zone”, the base of the wall is the “atmospheric front”. Length of the wall corresponds to the length of the frontal zone and the front line, the height corresponds to the vertical extent of the frontal zone). Front surface necessarily tilted, since air masses always differ in temperature - cold air (as more dense) flows under the warm one, trying to occupy the lowest position. Interaction air masses in the zone front causes the formation of clouds, precipitation, and is accompanied by changes in weather conditions.

Depending on what air mass , warm or cold , approaching to this point , are being formed warm or cold fronts .

If it's approaching warm air mass (front warm air ) the atmospheric front is called warm. Warm front , thus moving to the side cold air mass . Wherein warm air as lighter, smoother rises along the wedge cold air , forming a corresponding system of stratiform clouds. Typically driving speed warm front is 30-40 km/h, i.e. 720 – 960 km/day. Approximationwarm front leads to the replacement of cold air with warm air.

If it's approaching cold air mass(frontcold air), the atmospheric front is called cold .Cold front moves to the side warm air mass . Cold air is denser and heavier displaces warm air up. Approximationcold front results in the replacement of warm air with cold air.

Weather

Weather reflects complex of meteorological elements(weather elements) and atmospheric phenomena observed in the area in a certain limited period of time(analogue hydrological conditions).

Weather elements: atmospheric pressure, temperature and humidity.Weather phenomena : wind, number and shape of clouds, precipitation, aurora, rainbow, mirage, etc. Weather phenomena can be catastrophic: hurricane, thunderstorm, downpour, drought, blizzard, squall, dust storm and etc.

Weather in a warm atmospheric front .Before approachingwarm front the observation point was in the area cold air mass The weather is clear cold(cool, not very warm - depending on the season), little wind. As approachingwarm front is decreasingAtmosphere pressure ,increasesair temperature .Clouds become more and more dense, fall out blanket precipitation . Sometimes observed thunderstorms.After passing warm front (behind the front line) observation point turns out entirely in the regionwarm air . Air temperature increased.Precipitation stop,Atmosphere pressure downgraded,wind subsides.

weather in cold front .Before approachingfront the observation point was in the area warm air mass . The weather is clear warm, little wind. The cloud system as a whole similar cloud system of a warm front, but it is developing in reverse order.Before passing front lines as a result of more powerful upward air movement, cumulonimbus clouds , accompanied thunderstorms . Along the entire cold front lines there is a sharp increase in wind, acquiring the character squalls .After passing front lines the observation point is entirely in the area cold air . There is a noticeable (sometimes dramatic) ) Moving to a warmer surface (usually from high to low latitudes), they bring , clarification , suddencessation of precipitation , strongincrease in pressure ,wind subsides.

Weather in a cyclone. IN cyclone circulate twoair masses, resulting in twoatmospheric front . weather in cyclone determined propertiesair masses ,activitiesatmospheric fronts , ascending air flows in the center, the size pressure gradients,season of the year. Generally, weather in area cyclone usually cloudy, rainy, windy (to stormy), often with long fogs, winter with abundant snowfalls And snowstorms . Atmosphere pressure downgraded. In summercyclones bring cool weather, warming in winter.On the peripherycyclone weather relatively calm.

IN tropical cyclone Due to very large horizontal pressure gradients, the weather is particularly violent. Wind inside hurricane (typhoon) reaches a speed of 50-60 m/s, individual gusts exceed 100 m/s. It's pouring rain .Tropical cyclones have enormous destructive force often their passing accompanied by human casualties, sometimes quite numerous. To each tropical cyclone , having a storm intensity or higher, is assigned given name.Tropical cyclones bring huge damage, which is significantly reduced thanks to a well-established warning service. Tropical cyclones included in the category of dangerous (natural) phenomena.

(At the end of October 2012 in Caribbean Sea, where it was especially powerful (69 people died, including 54 Haitians) Hurricane Sandy arose. On October 28, although weakened, it reached the east coast of the United States. Great destruction, houses along the coast were washed away, power supply was disrupted, schools and government agencies were closed, some city subway stations were flooded in New York, 7-8 thousand flights were canceled, more than 94 people were killed, economic damage was about 50 billion dollars).

IN anticyclone one air mass circulates, since atmospheric fronts are carried by air currents diverging from the center to its periphery. Weather V anticyclone depends on time of year, states underlying surface, properties air mass and other factors. Generally, weather V anticyclone usuallyclear,little wind,atmospheric pressure increased.In summeranticyclones bring hot weather, in winter - cold, frosty, but sunny. On peripheryanticyclone usually happens cloudy weather With precipitation, in the zone of contact with cyclone observed strong winds.

Anticyclones often originate in the backcourt cyclone among the masses cold air, therefore, as a rule, anticyclone usually precedes cyclone .

Air masses are called large quantities air in the troposphere, measured in the horizontal direction by thousands of kilometers, having relatively homogeneous physical properties(mainly temperature and relative humidity). These properties within the air mass can change, but slowly, continuously, without jumps. They are set by the conditions of the region of the Earth where the formation of the air mass occurs (the nature of the underlying surface and the weather).

Favorable conditions for the formation of air masses are created in slow-moving anticyclones and cyclones, where air can remain over the same geographical area for a long time, called the source of air mass formation. The underlying surface should be monotonous or almost monotonous (desert, steppe, ocean surface, ice fields, etc.).

The formation of the air mass lasts from 3 to 10 days. How more time formation, the more clearly the properties are expressed. During the movement, transformations of air masses occur. Passing over the seas and oceans, they are moistened, over land they dry out, moving towards the pole they cool, towards the tropics they heat up.

Air masses are classified as follows:

According to thermodynamic criteria

• A cold air mass moves from a colder region to a warmer one. Its arrival usually leads to colder temperatures in the area. At the same time, it gradually warms up.
• Warm water moves from a warmer region to a colder one. Its arrival leads to warming in the area. Gradually cools down.
• The local one stays in the same area for a long time and retains its properties without much change. It can be both relatively cold and relatively warm, depending on the type of neighboring air mass and the radiation balance.

All three types of energy state can be:

• Stable - having a vertical temperature gradient in the lower layer that is less than the moist adiabatic one. Convective vertical movements do not develop and cumulus clouds do not form. Steady state is typical for a warm mass when moving to a colder surface, when it is cooled from below and small vertical gradients are created.
• Unstable - having a vertical temperature gradient greater than the moist-adiabatic one. The resulting vertical convection with a sufficient supply of moisture leads to the formation of cumulus clouds and precipitation. This condition is typical for cold masses entering the warm surface. In this case, the air warms up from below and large vertical temperature gradients arise.

Geographically

Of the many types, the main ones here are four:

• The Arctic (Antarctic) air mass is formed beyond the Arctic Circle. In the place of formation it is very stable, with low temperatures and low humidity.
• Polar or temperate is formed when air remains in temperate latitudes for a long time. Stability depends on the source of formation and direction of movement.
• The tropical one is formed in the zone of subtropical anticyclones. Warming up at the place of formation, therefore unstable, with high content moisture.
• Equatorial is formed in the equatorial zone.

Each of the listed air masses can be maritime or continental, depending on the underlying surface at the place of its formation.

Stability of air masses

Stable air masses

Stable is an air mass in which stable vertical equilibrium predominates, that is, in its main thickness the vertical temperature gradient is less than the moist adiabatic one. Thermal convection does not develop in the CFM, and dynamic convection is poorly developed. The average value of the vertical temperature gradient in the UVM is usually less than 0.6°/100 m. Inversion and isotherm layers (retention layers) are found here. Turbulent exchange clouds - stratus and stratocumulus - can appear in the UCM. If the condensation level is higher upper limit turbulent layer, then clear weather is observed. Significant precipitation is not observed in the UVM; in some cases, drizzle precipitation may fall from stratus clouds that have reached significant vertical thickness, and light snow may fall from stratocumulus clouds in winter. Due to the weak vertical exchange, haze and, in some cases, fog are usually observed in the UVM.

A warm stable air mass over the continents is observed, as a rule, in the cold half of the year, and enters this region in the warm sectors of cyclones and the adjacent northern outskirts of anticyclones. IN in some cases The vertical thickness of stratus clouds increases so much that they turn into nimbostratus clouds and begin to produce continuous precipitation. The vertical distribution of air temperature is represented by layers of inversion and isothermia, or small temperature gradients up to a height of 3-4 km.

A cold, stable air mass is observed over continents, mainly in winter. The main type is frosty, cloudless weather. Additional types include significant and continuous stratus and stratocumulus clouds with occasional light snowfall.

Unstable air masses

An unstable air mass is characterized by the fact that in its lower layers (approximately below 3 km) an unstable stratification of the atmosphere is observed. With unstable stratification, the vertical temperature gradient in the air mass up to the condensation level is greater than the dry-adiabatic gradient, and above the condensation level is greater than the moist-adiabatic gradient. In an unstable air mass with sufficient humidity, convection develops with the formation of vertical clouds, increased turbulence, strong gusty winds, showers, thunderstorms, and squalls are observed.

A cold air mass, moving to a warmer underlying surface and warming up from below, becomes, as a rule, an unstable air mass. A cold unstable air mass is most often observed over the mainland in the summer in the afternoon hours in the rear part of the cyclone or in the front part of the anticyclone.

Centers for the formation of air masses

The centers of formation of air masses are usually regions where the air descends and then spreads in the horizontal direction - anticyclonic systems meet this requirement. Anticyclones are more likely than cyclones to be low-moving, so the formation of air masses usually occurs in extensive low-moving (quasi-stationary) anticyclones.

In addition, the requirements of the source are met by slow-moving and diffuse thermal depressions that arise over heated land areas. Finally, the formation of polar air occurs partly in the upper atmosphere in slow-moving, extensive and deep central cyclones at high latitudes.

In these pressure systems, the transformation (conversion) of tropical air drawn into high latitudes in the upper troposphere into temperate air occurs.

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AIR MASSES, relatively homogeneous parts of the troposphere, comparable to in large parts continents and oceans, having certain general properties, moving as a single unit. Air masses cover areas of several million km2; vertically they rarely reach the tropopause, and more often cover only the lower half of the troposphere. Adjacent air masses separate from each other atmospheric fronts, up to several thousand km long and up to several tens of km wide. The main fronts (traced to the stratosphere) separate the main types of air masses, the secondary ones (altitude of several km) - air masses of the same type. The areas of formation of air masses are vast territories that are fairly homogeneous horizontally, over which the air mass acquires the same characteristics over the entire area. The air above such a territory must remain long enough to approach dynamic equilibrium with the underlying surface, i.e., acquire uniform weather characteristics typical of the area of ​​formation. The main weather characteristics of air masses are determined by the vertical distribution of temperature and humidity. Later, moving in one of the currents general circulation atmosphere, air masses also transfer their properties, that is, their weather regime. Characteristic climate regime regions of the Earth is determined by the predominance of a certain type of air mass in a given region in a given season.

By origin, air masses are distinguished: Arctic, Antarctic, temperate latitudes (polar), tropical and equatorial, with their division (except equatorial) into marine and continental types. Each type has its own vertical temperature gradients, humidity, transparency, etc. With long-term movement, air masses are transformed and their properties change. Air masses moving from high latitudes with a colder earth's surface to low latitudes with a warmer surface are called cold. They cause cooling in the areas into which they arrive, while warming up from the earth's surface, which contributes to the development of vertical gradients, convection with the formation of rain clouds and precipitation. Air masses moving from low, warmer latitudes to high latitudes are called warm, and they accordingly bring warming; They are characterized by small vertical temperature gradients, stratus clouds and fogs. Air masses that stay in one area for a long time are called local. Their properties depend on the time of year.

Lit.: Ocean - Atmosphere: Encyclopedia. L., 1983; Khromov S.P., Petrosyants M.A. Meteorology and climatology. 6th ed. M., 2004.