The diurnal variation of water vapor pressure. Daily and annual variation of air temperature near the earth's surface Daily and annual variation of air temperature

The daily and annual course of air temperature in the surface layer of the atmosphere is determined by the temperature at a height of 2 m. Basically, this course is due to the corresponding course of the temperature of the active surface. Features of the course of air temperature are determined by its extremes, that is, the highest and lowest temperatures. The difference between these temperatures is called the amplitude of the course of air temperature. The pattern of daily and annual variations in air temperature is revealed by averaging the results of long-term observations. It is associated with periodic fluctuations. Non-periodic disturbances of the daily and annual course, caused by the intrusion of warm or cold air masses, distort the normal course of air temperature. The heat absorbed by the active surface is transferred to the adjacent air layer. In this case, there is some delay in the increase and decrease in air temperature compared to changes in soil temperature. In the normal course of temperature, the minimum temperature is observed before sunrise, the maximum is observed at 14-15 hours (Fig. 4.4).

Figure 4.4. The daily course of air temperature in Barnaul(available when downloading the full version of the tutorial)

Amplitude of diurnal variation of air temperature over land is always less than the amplitude of the daily variation of soil surface temperature and depends on the same factors, that is, on the season, latitude, cloudiness, terrain, as well as on the nature of the active surface and altitude above sea level. Amplitude of the annual cycle calculated as the difference between the mean monthly temperatures of the warmest and coldest months. Absolute annual temperature amplitude called the difference between the absolute maximum and the absolute minimum air temperature for the year, that is, between the highest and lowest temperatures observed during the year. The amplitude of the annual course of air temperature in a given place depends on the geographic latitude, distance from the sea, altitude of the place, on the annual course of cloudiness and a number of other factors. Small annual temperature amplitudes are observed over the sea and are characteristic of the maritime climate. Over land, there are large annual temperature amplitudes characteristic of the continental climate. However, the maritime climate also extends to the regions of the continents adjacent to the sea, where the frequency of sea air masses is high. Sea air brings a maritime climate to land. With the distance from the ocean deep into the mainland, the annual temperature amplitudes increase, that is, the continentality of the climate increases.

By the value of the amplitude and by the time of onset of extreme temperatures, they distinguish four types of annual variation in air temperature. equatorial type It is characterized by two maxima - after the spring and autumn equinoxes, when the Sun is at its zenith at noon, and two minima - after the summer and earth solstices. This type is characterized by a small amplitude: over the continents within 5-10°C, and over the oceans only about 1°C. tropical type characterized by one maximum - after the summer solstice and one minimum - after the winter solstice. The amplitude increases with distance from the equator and averages 10-20°С over the continents and 5-10°С over the oceans. Temperate type characterized by the fact that extremes are observed over the continents at the same time as in the case of the tropical type, and over the ocean a month later. The amplitude increases with latitude, reaching 50-60°C over the continents and 15-20°C over the oceans. polar type similar to the previous type, but differs in a further increase in amplitude, reaching 25-40°С over the ocean and coasts, and exceeding 65°С over land

January and July isotherms on the territory of Russia??????

Lucas Rein Student (237) 1 year ago

THERMAL BELT OF THE EARTH, temperature zones of the Earth, - a system for classifying climates by air temperature. Usually distinguished: hot zone - between annual isotherms 20 ° (reaches 30 ° latitude); 2 temperate zones (in each hemisphere) - between the annual isotherm of 20 ° and the isotherm of the warmest month. 10°; 2 cold belts - between the isotherms of the warmest month. 10° and 0°; 2 belts of eternal frost - from cf. temperature of the warmest month. below 0°.

Juliette Student (237) 1 year ago

Thermal belts are wide bands encircling the Earth, with close air temperatures inside the belt and differing from neighboring ones by a non-uniform latitudinal distribution of solar radiation. There are seven thermal zones: hot on both sides of the equator, limited by annual isotherms of +20°C; temperate 2 (northern and southern) with a boundary isotherm of +10°С of the warmest month; cold 2 within +10°С and 0°С of the warmest month of eternal frost 2 with an average annual air temperature below 0°С.

Optical phenomena. As already mentioned, when the rays of the Sun pass through the atmosphere, part of the direct solar radiation is absorbed by air molecules, scattered and reflected. As a result of this, various optical phenomena are observed in the atmosphere, which are perceived directly by our eye. These phenomena include: sky color, refraction, mirages, halo, rainbow, false sun, light pillars, light crosses, etc.

Sky color. Everyone knows that the color of the sky changes depending on the state of the atmosphere. A clear cloudless sky during the day has a blue color. This color of the sky is due to the fact that there is a lot of scattered solar radiation in the atmosphere, which is dominated by short waves that we perceive as blue or blue. If the air is dusty, then the spectral composition of the scattered radiation changes, the blue of the sky weakens; the sky turns white. The more cloudy the air, the weaker the blue of the sky.

The color of the sky changes with height. At a height of 15 to 20 km the color of the sky is black and purple. From the tops of high mountains, the color of the sky seems deep blue, and from the surface of the Earth - blue. This change in color from black-violet to light blue is due to the ever-increasing scattering of first violet, then blue and blue rays.

At sunrise and sunset, when the sun's rays pass through the greatest thickness of the atmosphere and at the same time lose almost all short-wave rays (violet and blue), and only long-wave rays reach the observer's eye, the color of the part of the sky near the horizon and the Sun itself has a red or orange color .

Refraction. As a result of the reflection and refraction of the sun's rays as they pass through layers of air of different density, their trajectory undergoes some changes. This leads to the fact that we see celestial bodies and distant objects on the earth's surface in a direction slightly different from the one in which they are actually located. For example, if we look at the top of a mountain from a valley, then the mountain seems to us to be elevated; when sighting from the mountain into the valley, an increase in the bottom of the valley is noticed.

The angle formed by a straight line from the observer's eye to a point and the direction in which the eye sees that point is called refraction.

The amount of refraction observed at the earth's surface depends on the distribution of the density of the lower layers of air and on the distance from the observer to the object. The density of air depends on temperature and pressure. On average, the magnitude of the earth's refraction, depending on the distance to the observed objects under normal atmospheric conditions, is:

Mirages. Mirage phenomena are associated with anomalous refraction of the sun's rays, which is caused by a sharp change in air density in the lower atmosphere. With a mirage, the observer sees, in addition to objects, their images are also lower or higher than the actual position of the objects, and sometimes to the right or left of them. Often the observer can only see the image without seeing the objects themselves.

If the air density drops sharply with height, then the image of objects is observed above their actual location. So, for example, under such conditions, you can see the silhouette of the ship above sea level, when the ship is hidden from the observer beyond the horizon.

Inferior mirages are often observed on open plains, especially in deserts, where air density increases sharply with height. In this case, a person often sees in the distance, as it were, a watery, slightly undulating surface. If at the same time there are any objects on the horizon, then they seem to rise above this water. And in this water space one can see their outlines turned upside down, as if reflected in the water. The visibility of the water surface on the plain is created as a result of a large refraction, which causes an inverse image below the earth's surface of a part of the sky behind objects.

Halo. The phenomenon of a halo refers to light or iridescent circles, sometimes observed around the Sun or Moon. A halo occurs when these celestial bodies have to be seen through light cirrus clouds or through a veil of fog, consisting of ice needles suspended in the air (Fig. 63).

The phenomenon of the halo occurs due to refraction in ice crystals and reflection from their faces of the sun's rays.

Rainbow. A rainbow is a large multi-colored arc, usually observed after rain against the background of rain clouds located against that part of the sky where the Sun shines. The magnitude of the arc is different, sometimes there is a full iridescent semicircle. We often see two rainbows at the same time. The intensity of development of individual colors in the rainbow and the width of their bands are different. In a well-visible rainbow, red is located on one side and purple on the other; the rest of the colors in the rainbow are in the order of the colors of the spectrum.

Rainbows are caused by the refraction and reflection of sunlight in water droplets in the atmosphere.

Sound phenomena in the atmosphere. Longitudinal vibrations of particles of matter, propagating through the material medium (through air, water and solids) and reaching the human ear, cause sensations called "sound".

Atmospheric air always contains sound waves of various frequencies and strengths. Some of these waves are created artificially by man, and some of the sounds are of meteorological origin.

Sounds of meteorological origin include thunder, the howl of the wind, the hum of wires, the noise and rustle of trees, the "voice of the sea", the sounds and noises that occur during the movement of sand masses in deserts and over dunes, as well as snowflakes over a smooth surface of snow, sounds when falling on the earth's surface of solid and liquid precipitation, the sounds of the surf near the shores of the seas and lakes, etc. Let us dwell on some of them.

Thunder is observed during the phenomena of a lightning discharge. It arises in connection with the special thermodynamic conditions that are created on the path of lightning movement. Usually we perceive thunder in the form of a series of blows - the so-called peals. Thunderclaps are explained by the fact that sounds generated at the same time along the long and usually winding path of lightning reach the observer sequentially and with different intensities. Thunder, despite the great power of sound, is heard at a distance of no more than 20-25 km(average about 15 km).

The howl of the wind occurs when the air moves rapidly with a swirl of some objects. In this case, there is an alternation of accumulation and outflow of air from objects, which gives rise to sounds. The buzz of wires, the noise and rustle of trees, the "voice of the sea" are also connected by air movement.

The speed of sound in the atmosphere. The speed of sound propagation in the atmosphere is affected by the temperature and humidity of the air, as well as the wind (direction and its strength). The average speed of sound in the atmosphere is 333 m per second. As the air temperature increases, the speed of sound increases slightly. A change in the absolute humidity of the air has a smaller effect on the speed of sound. The wind has a strong influence: the speed of sound in the direction of the wind increases, against the wind it decreases.

Knowledge of the speed of sound propagation in the atmosphere is of great importance in solving a number of problems in studying the upper layers of the atmosphere by the acoustic method. Using the average speed of sound in the atmosphere, you can find out the distance from your location to the location of the thunder. To do this, you need to determine the number of seconds between the visible flash of lightning and the moment the sound of thunder arrives. Then you need to multiply the average value of the speed of sound in the atmosphere - 333 m/sec. for the given number of seconds.

Echo. Sound waves, like light rays, experience refraction and reflection when passing from one medium to another. Sound waves can be reflected from the earth's surface, from water, from surrounding mountains, clouds, from the interface between air layers that have different temperatures and humidity. The sound, reflected, can be repeated. The phenomenon of repetition of sounds due to the reflection of sound waves from different surfaces is called "echo".

Especially often the echo is observed in the mountains, near the rocks, where a loudly spoken word is repeated one or several times after a certain period of time. So, for example, in the Rhine Valley there is a Lorelei rock, in which the echo is repeated up to 17-20 times. An example of an echo is the peals of thunder, which arise as a result of the reflection of the sounds of electrical discharges from various objects on the earth's surface.

Electrical phenomena in the atmosphere. Electrical phenomena observed in the atmosphere are associated with the presence in the air of electrically charged atoms and gas molecules called ions. Ions come in both negative and positive charges, and according to the size of the masses are divided into light and heavy. The ionization of the atmosphere occurs under the influence of the short-wave part of solar radiation, cosmic rays and radiation of radioactive substances contained in the earth's crust and in the atmosphere itself. The essence of ionization lies in the fact that these ionizers transfer energy to a neutral molecule or atom of air gas, under the action of which one of the outer electrons is removed from the sphere of action of the nucleus. As a result, an atom deprived of one electron becomes a positive light ion. An electron removed from a given atom quickly joins a neutral atom and in this way a negative light ion is created. Light ions, meeting with suspended particles of air, give them their charge and thus form heavy ions.

The number of ions in the atmosphere increases with height. On average for every 2 km height, their number increases by a thousand ions in one cubic meter. centimeter. In the high layers of the atmosphere, the maximum concentration of ions is observed at altitudes of about 100 and 250 km.

The presence of ions in the atmosphere creates the electrical conductivity of the air and the electric field in the atmosphere.

The conductivity of the atmosphere is created due to the high mobility of mainly light ions. Heavy ions play a small role in this respect. The higher the concentration of light ions in the air, the greater its conductivity. And since the number of light ions increases with height, the conductivity of the atmosphere also increases with height. So, for example, at a height of 7-8 km conductivity is approximately 15-20 times greater than that of the earth's surface. At about 100 km conductivity is very high.

Clean air has few suspended particles, so it contains more light ions and fewer heavy ones. In this regard, the conductivity of clean air is higher than the conductivity of dusty air. Therefore, in haze and fog, conductivity has a low value. The electric field in the atmosphere was first established by M. V. Lomonosov. In clear cloudless weather, the field strength is considered normal. Towards

Earth's surface atmosphere is positively charged. Under the influence of the electric field of the atmosphere and the negative field of the earth's surface, a vertical current of positive ions is established from the earth's surface upwards, and negative ions from the atmosphere downwards. The electric field of the atmosphere near the earth's surface is extremely variable and depends on the conductivity of the air. The lower the conductivity of the atmosphere, the greater the electric field strength of the atmosphere. The conductivity of the atmosphere mainly depends on the amount of solid and liquid particles suspended in it. Therefore, during haze, during precipitation and fog, the intensity of the electric field of the atmosphere increases and this often leads to electric discharges.

Elm's Lights. During thunderstorms and squalls in summer or snowstorms in winter, one can sometimes observe quiet electrical discharges on the tips of objects protruding above the earth's surface. These visible discharges are called "Elmo's fires" (Fig. 64). Most often, Elmo's lights are observed on masts, on mountain tops; sometimes they are accompanied by a slight crackle.

Elmo fires are formed at a high electric field strength. The tension is so great that ions and electrons, moving at high speed, split air molecules on their way, which increases the number of ions and electrons in the air. In this regard, the conductivity of the air increases and from sharp objects where electricity accumulates, the outflow of electricity and discharge begins.

Lightning. As a result of complex thermal and dynamic processes in thunderclouds, electric charges are separated: usually negative charges are located at the bottom of the cloud, positive charges at the top. In connection with such a separation of space charges inside the clouds, strong electric fields are created both inside the clouds and between them. In this case, the field strength near the earth's surface can reach several hundred kilovolts per 1 m. A large electric field strength leads to the fact that electric discharges occur in the atmosphere. Strong sparking electrical discharges that occur between thunderclouds or between clouds and the earth's surface are called lightning.

The duration of a lightning flash is on average about 0.2 sec. The amount of electricity that lightning carries is 10-50 coulombs. The current strength is very large; sometimes it reaches 100-150 thousand amperes, but in most cases it does not exceed 20 thousand amperes. Most lightning is negatively charged.

According to the appearance of the spark flash, lightning is divided into linear, flat, ball, and beaded.

The most frequently observed linear lightning, among which there are a number of varieties: zigzag, branched, ribbon, rocket, etc. If linear lightning is formed between the cloud and the earth's surface, then its average length is 2-3 km; lightning between clouds can reach 15-20 km length. The discharge channel of lightning, which is created under the influence of air ionization and through which there is an intense counter-flow of negative charges accumulated in clouds and positive charges accumulated on the earth's surface, has a diameter of 3 to 60 cm.

Flat lightning is a short-term electrical discharge covering a significant part of the cloud. Flat lightning is not always accompanied by thunder.

Ball lightning is a rare occurrence. It is formed in some cases after a strong discharge of linear lightning. Ball lightning is a fireball with a diameter of usually 10-20 cm(and sometimes up to several meters). On the earth's surface, this lightning moves at a moderate speed and has a tendency to penetrate inside buildings through chimneys and other small openings. Without causing harm and having done complex movements, ball lightning can safely leave the building. Sometimes it causes fires and destruction.

An even rarer occurrence is beaded lightning. They occur when an electric discharge consists of a series of luminous spherical or oblong bodies.

Lightning often causes great damage; they destroy buildings, start fires, melt electrical wires, split trees, and injure people. To protect buildings, industrial structures, bridges, power plants, power lines and other structures from direct lightning strikes, lightning rods are used (usually they are called lightning rods).

The greatest number of days with thunderstorms is observed in tropical and equatorial countries. So, for example, on about. Java has 220 days with thunderstorms in a year, 150 days in Central Africa, about 140 in Central America. In the USSR, the most days with thunderstorms occur in the Caucasus (up to 40 days a year), in Ukraine and in the southeast of the European part of the USSR. Thunderstorms are usually observed in the afternoon, especially between 15 and 18 hours.

Polar Lights. Auroras are a peculiar form of glow in the high layers of the atmosphere, observed at times at night, mainly in the polar and circumpolar countries of the northern and southern hemispheres (Fig. 65). These glows are a manifestation of the electrical forces of the atmosphere and occur at an altitude of 80 up to 1000 km in highly rarefied air when electric charges pass through it. The nature of the auroras has not yet been fully unraveled, but it has been precisely established that the cause of their occurrence is

the impact of the upper highly rarefied layers of the earth's atmosphere of charged particles (corpuscles) entering the atmosphere from active regions of the sun (spots, prominences and other areas) during solar flares.

The maximum number of auroras is observed near the Earth's magnetic poles. So, for example, at the magnetic pole of the northern hemisphere, there are up to 100 auroras per year.

According to the shape of the glow, the auroras are very diverse, but they are usually divided into two main groups: auroras of a non-beam form (uniform stripes, arcs, calm and pulsating luminous surfaces, diffuse glows, etc.) and auroras of a radiant structure (stripes, drapes, rays, corona and etc.). Auroras of a beamless structure are characterized by a calm glow. The radiances of the ray structure, on the contrary, are mobile, they change both the shape and the brightness and color of the glow. In addition, auroras of radiant form are accompanied by magnetic excitations.

The following types of precipitation are distinguished according to the form. Rain- liquid precipitation, consisting of drops with a diameter of 0.5-6 mm. Larger droplets break into pieces as they fall. In torrential rains, the size of the drops is larger than in continuous ones, especially at the beginning of the rain. At negative temperatures, supercooled drops can sometimes fall out. In contact with the earth's surface, they freeze and cover it with an ice crust. Drizzle - liquid precipitation, consisting of drops with a diameter of about 0.5-0.05 mm with a very low falling speed. They are easily carried by the wind in a horizontal direction. Snow- solid precipitation, consisting of complex ice crystals (snowflakes). Their forms are very diverse and depend on the conditions of education. The main form of snow crystals is a six-pointed star. Stars are obtained from hexagonal plates, because the sublimation of water vapor occurs most rapidly at the corners of the plates, where the rays grow. On these rays, in turn, branches are created. The diameters of the falling snowflakes can be very different grits, snow and ice, - precipitation consisting of icy and heavily grained snowflakes with a diameter of more than 1 mm. Most often, croup is observed at temperatures close to zero, especially in autumn and spring. Snow groats have a snow-like structure: grains are easily compressed by fingers. Nuclei of ice grains have a icy surface. It is difficult to crush them; when they fall to the ground, they jump. From stratus clouds in winter instead of drizzle fall snow grains- small grains with a diameter of less than 1 mm, resembling semolina. In winter, at low temperatures, sometimes fall out of the clouds of the lower or middle tier snow needles- sediments consisting of ice crystals in the form of hexagonal prisms and plates without branching. With significant frosts, such crystals can occur in the air near the earth's surface. They are especially well seen on a sunny day, when their facets sparkle, reflecting the sun's rays. Clouds of the upper tier are composed of such ice needles. Has a special character freezing rain- precipitation consisting of transparent ice balls (raindrops frozen in the air) with a diameter of 1-3 mm. Their loss clearly indicates the presence of a temperature inversion. Somewhere in the atmosphere there is a layer of air with a positive temperature

In recent years, several methods have been proposed and successfully tested for the artificial precipitation of clouds and the formation of precipitation from them. To do this, small particles (“grains”) of solid carbon dioxide having a temperature of about -70 ° C are scattered from an aircraft in a supercooled drop cloud. Due to such a low temperature, a huge number of very small ice crystals form around these grains in the air. These crystals are then dispersed in the cloud due to the movement of air. They serve as the germs on which large snowflakes later grow - exactly as described above (§ 310). In this case, a wide (1-2 km) gap is formed in the cloud layer along the entire path that the aircraft has traveled (Fig. 510). The resulting snowflakes can create quite a heavy snowfall. It goes without saying that only as much water can be precipitated in this way as was previously contained in the cloud. To strengthen the process of condensation and the formation of primary, smallest cloud drops is not yet within the power of man.

Clouds- products of water vapor condensation suspended in the atmosphere, visible in the sky from the surface of the earth.

Clouds are made up of tiny drops of water and/or ice crystals (called cloud elements). Droplet cloud elements are observed when the air temperature in the cloud is above −10 °C; from -10 to -15 °C, clouds have a mixed composition (drops and crystals), and at temperatures in the cloud below -15 °C, they are crystalline.

Clouds are classified into a system that uses Latin words for the appearance of clouds as seen from the ground. The table summarizes the four main components of this classification system (Ahrens, 1994).

Further classification describes the clouds according to their height. For example, clouds containing the prefix "cirr-" in their name as cirrus clouds are located in the upper tier, while clouds with the prefix " alto-" in the name, such as high-stratus (altostratus), are in the middle tier. Several groups of clouds are distinguished here. The first three groups are determined by their height above the ground. The fourth group consists of clouds of vertical development. The last group includes a collection of mixed types clouds.

Lower clouds Lower clouds are mostly composed of water droplets because they are located at altitudes below 2 km. However, when temperatures are low enough, these clouds can also contain ice particles and snow.

Clouds of vertical development These are cumulus clouds that look like isolated cloud masses, the vertical dimensions of which are of the same order as the horizontal ones. They are usually called temperature convection or front lift, and can grow to heights of 12 km, realizing the growing energy through condensation water vapor within the cloud itself.

Other types of clouds Finally, we present collections of mixed cloud types that do not fit into any of the four previous groups.

Most of Russia is characterized by moderate rainfall. In the Aral-Caspian and Turkestan steppes, as well as in the far North, they even fall very little. Very rainy areas include only some of the southern outskirts of Russia, especially Transcaucasia.

Pressure

Atmosphere pressure- the pressure of the atmosphere on all objects in it and the earth's surface. Atmospheric pressure is created by the gravitational attraction of air to the Earth. Atmospheric pressure is measured with a barometer. Atmospheric pressure equal to the pressure of a column of mercury 760 mm high at 0 °C is called normal atmospheric pressure. (International standard atmosphere - ISA, 101 325 Pa

The presence of atmospheric pressure confused people in 1638, when the idea of ​​the Duke of Tuscany to decorate the gardens of Florence with fountains failed - the water did not rise above 10.3 meters. The search for the reasons for this and experiments with a heavier substance - mercury, undertaken by Evangelista Torricelli, led to the fact that in 1643 he proved that air has weight. Together with V. Viviani, Torricelli conducted the first experiment on measuring atmospheric pressure, inventing pipe Torricelli(the first mercury barometer) - a glass tube in which there is no air. In such a tube, mercury rises to a height of about 760 mm. Measurementpressure necessary for process control and production safety. In addition, this parameter is used for indirect measurements of other process parameters: level, flow, temperature, density etc. In the SI system, the unit of pressure is taken pascal (Pa) .

In most cases, primary pressure transducers have a non-electrical output signal in the form of force or displacement and are combined in one unit with a measuring device. If the measurement results must be transmitted over a distance, then an intermediate conversion of this non-electrical signal into a unified electrical or pneumatic signal is used. In this case, the primary and intermediate converters are combined into one measuring converter.

Used to measure pressure pressure gauges, vacuum gauges, combined pressure and vacuum meters, pressure gauges, thrust gauges, thrust gauges, Pressure Sensors, differential pressure gauges.

In most devices, the measured pressure is converted into a deformation of elastic elements, so they are called deformation.

Deformation devices are widely used to measure pressure in the conduct of technological processes due to the simplicity of the device, convenience and safety in operation. All deformation devices have some kind of elastic element in the circuit, which is deformed under the action of the measured pressure: tubular spring, membrane or bellows.

Distribution

On the earth's surface Atmosphere pressure varies from place to place and over time. Non-periodic changes are especially important Atmosphere pressure associated with the emergence, development and destruction of slowly moving high pressure areas - anticyclones and relatively fast moving huge whirlwinds - cyclones, where low pressure prevails. Extreme values ​​noted so far Atmosphere pressure(at sea level): 808.7 and 684.0 mmHg cm. However, despite the large variability, the distribution of monthly averages Atmosphere pressure on the surface of the globe every year is about the same. Average annual Atmosphere pressure lowered near the equator and has a minimum of 10 ° N. sh. Further Atmosphere pressure rises and reaches a maximum at 30-35 ° north and south latitude; then Atmosphere pressure decreases again, reaching a minimum at 60-65°, and rises again towards the poles. For this latitudinal distribution Atmosphere pressure the time of year and the nature of the distribution of continents and oceans have a significant influence. Over cold continents in winter there are areas of high Atmosphere pressure So the latitudinal distribution Atmosphere pressure is disturbed, and the pressure field breaks up into a series of high and low pressure areas, which are called centers of action of the atmosphere. With height, the horizontal distribution of pressure becomes simpler, approaching the latitudinal one. Starting from a height of about 5 km Atmosphere pressure throughout the globe decreases from the equator to the poles. In the daily course Atmosphere pressure 2 maxima are detected: at 9-10 h and 21-22 h, and 2 lows: in 3-4 h and 15-16 h. It has a particularly regular daily course in tropical countries, where the daily fluctuation reaches 2.4 mmHg Art., and night - 1.6 mmHg cm. With increasing latitude, the amplitude of change Atmosphere pressure decreases, but at the same time non-periodic changes become stronger Atmosphere pressure

The air is constantly moving: it rises - an upward movement, it falls - a downward movement. The movement of air in a horizontal direction is called wind. The reason for the occurrence of wind is the uneven distribution of air pressure on the surface of the Earth, which is caused by an uneven distribution of temperature. In this case, the air flow moves from places with high pressure to the side where the pressure is less. With the wind, the air does not move evenly, but in shocks, gusts, especially near the surface of the Earth. There are many reasons that affect the movement of air: the friction of the air flow on the surface of the Earth, encountering obstacles, etc. In addition, air flows under the influence of the rotation of the Earth deviate to the right in the northern hemisphere, and to the left in the southern hemisphere. Wind is characterized by speed, direction and strength. Wind speed is measured in meters per second (m/s), kilometers per hour (km/h), points (on the Beaufort scale from 0 to 12, currently up to 13 points). The wind speed depends on the pressure difference and is directly proportional to it: the greater the pressure difference (horizontal baric gradient), the greater the wind speed. The average long-term wind speed at the earth's surface is 4-9 m/s, rarely more than 15 m/s. In storms and hurricanes (temperate latitudes) - up to 30 m/s, in gusts up to 60 m/s. In tropical hurricanes, wind speeds reach up to 65 m/s, and in gusts they can reach 120 m/s. The direction of the wind is determined by the side of the horizon from which the wind is blowing. To designate it, eight main directions (rhumbs) are used: N, NW, W, SW, S, SE, B, NE. The direction depends on the pressure distribution and on the deflecting effect of the Earth's rotation. The strength of the wind depends on its speed and shows what dynamic pressure the air flow exerts on any surface. Wind strength is measured in kilograms per square meter (kg/m2). Winds are extremely diverse in origin, nature and significance. So, in temperate latitudes, where western transport dominates, westerly winds (NW, W, SW) prevail. These areas occupy vast spaces - from about 30 to 60 in each hemisphere. In the polar regions, winds blow from the poles to low pressure zones of temperate latitudes. These areas are dominated by northeasterly winds in the Arctic and southeasterly winds in the Antarctic. At the same time, the southeast winds of the Antarctic, in contrast to the Arctic ones, are more stable and have high speeds. The most extensive wind zone of the globe is located in tropical latitudes, where the trade winds blow. The trade winds are the constant winds of tropical latitudes. They are common in the zone from 30s. sh. up to 30. sh. , that is, the width of each zone is 2-2.5 thousand km. These are steady winds of moderate speed (5-8 m/s). At the earth's surface, due to friction and the deflecting action of the Earth's daily rotation, they have a predominant northeasterly direction in the northern hemisphere and southeasterly in the southern hemisphere (Fig. IV.2). They are formed because in the equatorial belt, heated air rises, and tropical air comes in its place from the north and south. The trade winds were and are of great practical importance in navigation, especially earlier for the sailing fleet, when they were called "trade winds". These winds form stable surface currents in the ocean along the equator, directed from east to west. It was they who brought the caravels of Columbus to America. Breezes are local winds that blow from sea to land during the day and from land to sea at night. In this regard, day and night breezes are distinguished. The daytime (sea) breeze is formed as a result of the fact that during the day the land heats up faster than the sea, and a lower pressure is established above it. At this time, over the sea (more chilled), the pressure is higher and the air begins to move from the sea to the land. The night (coastal) breeze blows from land to sea, since at this time the land cools faster than the sea, and reduced pressure is above the water surface - air moves from the coast to the sea.

Wind speed at weather stations is measured with anemometers; if the device is self-recording, then it is called an anemograph. Anemorumbograph determines not only the speed, but also the direction of the wind in the mode of constant registration. Instruments for measuring wind speed are installed at a height of 10-15 m above the surface, and the wind measured by them is called the wind near the earth's surface.

The direction of the wind is determined by naming the point on the horizon from where the wind blows or the angle formed by the direction of the wind with the meridian of the place where the wind blows, i.e. its azimuth. In the first case, 8 main points of the horizon are distinguished: north, northeast, east, southeast, south, southwest, west, northwest and 8 intermediate ones. 8 main directions of the direction have the following abbreviations (Russian and international): С-N, Yu-S, З-W, В-E, СЗ-NW, СВ-NE, SW-SW, SE- SE.

Air masses and fronts

Air masses are called relatively homogeneous air masses in terms of temperature and humidity, which spread over an area of ​​​​several thousand kilometers and several kilometers in height.

They are formed under conditions of a long stay on more or less homogeneous surfaces of land or the ocean. Moving in the process of general circulation of the atmosphere to other areas of the Earth, air masses are transported to these areas and their own weather regime. The dominance of certain air masses in a given region in a given season creates characteristic climatic regime of the area.

There are four main geographical types of air masses that cover the entire troposphere of the Earth. These are the masses of the Arctic (Antarctic), temperate, tropical and equatorial air. With the exception of the rest, in each of them, marine and continental varieties are also distinguished, which are formed in accordance with land and ocean .

Polar (Arctic and Antarctic) air forms over the ice surfaces of the polar regions and is characterized by low temperatures, low moisture content and good transparency.

Moderate air is much better warmed up, it is marked in summer by an increased moisture content, especially over the ocean. The prevailing western winds and cyclones of sea temperate air are transported and Aleko to the depths of the continents, often accompanying their way with precipitation

Tropical air is generally characterized by high temperatures. But if over the sea it is also very humid, then over land, on the contrary, it is extremely dry and dusty.

Equatorial air is marked by constant high temperatures and increased moisture content both over the ocean and over land. In the afternoon, there are frequent heavy rains.

Air masses with different temperatures and humidity are constantly moving and meet each other in a narrow space. The conditional surface separating the air masses is called the atmospheric front. When this imaginary surface intersects with the earth's surface, the so-called atmospheric front line is formed.

The surface separating arctic (antarctic) and temperate air is called the arctic and antarctic fronts, respectively. Air from temperate latitudes and tropics separates the polar front. Since the density of warm air is less than the density of cold air, the front is an inclined plane that always slopes towards cold air. at a very small angle (less than 1 °) to the surface of the earth. Cold air, as thicker, when meeting with warm air, seems to swim under it and lift it up, causing the formation of XMAmar.

Having met, various air masses continue to move in the direction of the mass, which moved at a higher speed. At the same time, the position of the frontal surface that separates these air masses changes, depending on the direction of movement of the frontal surface, cold and warm fronts are distinguished. cold After the passage of a cold front, atmospheric pressure rises and air humidity decreases. When warm air advances and the front moves towards lower temperatures, the front is called warm. When a warm front passes, warming occurs, the pressure decreases, and the temperature rises.

Fronts are of great importance for the weather, since clouds form near them and precipitation often falls. In places where warm and cold air meet, cyclones originate and develop, the weather becomes bad. Knowing the location of atmospheric fronts, the direction and speed of their movement, as well as having meteorological data, characterizing air masses, make weather forecasts.

Anticyclone- an area of ​​high 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.

A high anticyclone is warm and retains closed isobars with anticyclonic circulation even in the upper troposphere. Sometimes the anticyclone is multicenter. The air in the anticyclone in the northern hemisphere moves around the center clockwise (that is, deviates from the baric gradient to the right), in the southern hemisphere - counterclockwise. The anticyclone is characterized by the predominance of clear or slightly cloudy weather. Due to the cooling of air from the earth's surface in the cold season and at night in the anticyclone, the formation of surface inversions and low stratus clouds (St) and fogs is possible. In summer, moderate daytime convection with the formation of cumulus clouds is possible over land. Convection with the formation of cumulus clouds is also observed in the trade winds on the periphery of subtropical anticyclones facing the equator. When an anticyclone stabilizes at low latitudes, powerful, high and warm subtropical anticyclones arise. The stabilization of anticyclones also occurs in the middle and polar latitudes. High, slow-moving anticyclones that disrupt the general westerly transfer of mid-latitudes are called blocking anticyclones.

Synonyms: high pressure area, high pressure area, baric maximum.

Anticyclones reach a size of several thousand kilometers in diameter. In the center of the anticyclone, the pressure is usually 1020-1030 mbar, but can reach 1070-1080 mbar. Like cyclones, anticyclones move in the direction of the general air transport in the troposphere, that is, from west to east, while deviating to low latitudes. The average speed of the anticyclone movement is about 30 km/h in the Northern Hemisphere and about 40 km/h in the Southern Hemisphere, but often the anticyclone becomes inactive for a long time.

Signs of an anticyclone:

Clear or partly cloudy weather

No wind

No precipitation

Stable weather pattern (does not change noticeably over time as long as an anticyclone exists)

In summer, the anticyclone brings hot, cloudy weather. In winter, the anticyclone brings severe frosts, sometimes frosty fog is also possible.

An important feature of anticyclones is their formation in certain areas. In particular, anticyclones form over ice fields. And the more powerful the ice cover, the more pronounced the anticyclone; that is why the anticyclone over Antarctica is very powerful, and over Greenland it is low-power, over the Arctic it is medium in severity. Powerful anticyclones also develop in the tropical zone.

Cyclone(from other Greek κυκλῶν - “rotating”) - an atmospheric vortex of huge (from hundreds to several thousand kilometers) diameter with reduced air pressure in the center.

Air movement (dashed arrows) and isobars (solid lines) in a cyclone in the northern hemisphere.

Vertical section of a tropical cyclone

Air in cyclones circulates counterclockwise in the northern hemisphere and clockwise in the southern. In addition, in air layers at a height from the earth's surface up to several hundred meters, the wind has a term directed towards the center of the cyclone along the baric gradient (in the direction of decreasing pressure). The value of the term decreases with height.

Schematic representation of the process of formation of cyclones (black arrows) due to the rotation of the Earth (blue arrows).

A cyclone is not just the opposite of an anticyclone, they have a different mechanism of occurrence. Cyclones constantly and naturally appear due to the rotation of the Earth, thanks to the Coriolis force. A consequence of Brouwer's fixed point theorem is the presence of at least one cyclone or anticyclone in the atmosphere.

There are two main types of cyclones - extratropical and tropical. The first are formed in temperate or polar latitudes and have a diameter of thousands of kilometers at the beginning of development, and up to several thousand in the case of the so-called central cyclone. Among the extratropical cyclones, southern cyclones are distinguished, which form on the southern border of temperate latitudes (Mediterranean, Balkan, Black Sea, South Caspian, etc.) and shift to the north and northeast. Southern cyclones have colossal reserves of energy; It is with the southern cyclones in central Russia and the CIS that the heaviest precipitation, winds, thunderstorms, squalls and other weather phenomena are associated.

Tropical cyclones form in tropical latitudes and are smaller (hundreds, rarely more than a thousand kilometers), but have larger baric gradients and wind speeds reaching pre-storm levels. Such cyclones are also characterized by the so-called. "eye of the storm" - a central area with a diameter of 20-30 km with relatively clear and calm weather. Tropical cyclones can transform into extratropical cyclones during their development. Below 8-10 ° north and south latitude, cyclones occur very rarely, and in the immediate vicinity of the equator they do not occur at all.

Cyclones occur not only in the Earth's atmosphere, but also in the atmospheres of other planets. For example, in the atmosphere of Jupiter, the so-called Great Red Spot has been observed for many years, which is, apparently, a long-lived anticyclone.

The daily course of air temperature is the change in air temperature during the day - in general, it reflects the course of the temperature of the earth's surface, but the moments of the onset of maxima and minima are somewhat late, the maximum occurs at 2 pm, the minimum after sunrise.

The daily amplitude of air temperature (the difference between the maximum and minimum air temperatures during the day) is higher on land than over the ocean; decreases when moving to high latitudes (the greatest in tropical deserts - up to 400 C) and increases in places with bare soil. The magnitude of the daily amplitude of air temperature is one of the indicators of the continentality of the climate. In deserts, it is much greater than in areas with a maritime climate.

The annual course of air temperature (change in the average monthly temperature during the year) is determined, first of all, by the latitude of the place. The annual amplitude of air temperature is the difference between the maximum and minimum average monthly temperatures.

Theoretically, one would expect that the diurnal amplitude, i.e., the difference between the highest and lowest temperatures, would be greatest near the equator, because there the sun is much higher during the day than at higher latitudes, and even reaches the zenith at noon on the days of the equinox, i.e., it sends out vertical rays and therefore gives the greatest amount of heat. But this is not actually observed, since, in addition to latitude, many other factors also influence the daily amplitude, the totality of which determines the magnitude of the latter. In this regard, the position of the area relative to the sea is of great importance: whether the given area represents land, remote from the sea, or an area close to the sea, for example, an island. On the islands, due to the softening influence of the sea, the amplitude is insignificant, it is even less on the seas and oceans, but in the depths of the continents it is much greater, and the magnitude of the amplitude increases from the coast into the interior of the continent. At the same time, the amplitude also depends on the time of year: in summer it is larger, in winter it is smaller; the difference is explained by the fact that in summer the sun is higher than in winter, and the duration of the summer day is much longer than that of winter. Further, cloud cover influences the diurnal amplitude: it moderates the temperature difference between day and night, retaining the heat emitted by the earth at night, and at the same time moderating the action of the sun's rays.

The most significant daily amplitude is observed in deserts and high plateaus. Desert rocks, completely devoid of vegetation, become very hot during the day and quickly radiate all the heat received during the day during the night. In the Sahara, the daily air amplitude was observed at 20-25° and more. There were cases when, after a high daytime temperature, the water even froze at night, and the temperature on the surface of the earth fell below 0 °, and in the northern parts of the Sahara even to -6, -8 °, rising much higher than 30 ° during the day.

The daily amplitude is much less in areas covered with rich vegetation. Here, part of the heat received during the day is spent on the evaporation of moisture by plants, and, in addition, the vegetation cover protects the earth from direct heating, while at the same time delaying radiation at night. On high plateaus, where the air is considerably rarefied, the balance of heat inflow and outflow at night is sharply negative, and during the day it is sharply positive, so the daily amplitude here is sometimes greater than in deserts. For example, Przhevalsky, during his trip to Central Asia, observed in Tibet a daily fluctuation in air temperature, even up to 30 °, and on the high plateaus of the southern part of North America (in Colorado and Arizona), daily fluctuations, as observations showed, reached 40 °. Insignificant fluctuations in daily temperature are observed: in polar countries; for example, on Novaya Zemlya the amplitude does not exceed 1–2 on average even in summer. At the poles and in general in high latitudes, where the sun does not appear at all during the day or months, at this time there are absolutely no daily temperature fluctuations. It can be said that the daily course of temperature merges with the annual one at the poles, and winter represents night, and summer represents day. Of exceptional interest in this respect are the observations of the Soviet drifting station "North Pole".

Thus, we observe the highest daily amplitude: not at the equator, where it is about 5 ° on land, but closer to the tropic of the northern hemisphere, since it is here that the continents have the greatest extent, and here the greatest deserts and plateaus are located. The annual temperature amplitude depends mainly on the latitude of the place, but, in contrast to the daily temperature, the annual amplitude increases with distance from the equator to the pole. At the same time, the annual amplitude is influenced by all the factors that we have already dealt with when considering daily amplitudes. In the same way, fluctuations increase with distance from the sea deep into the mainland, and the most significant amplitudes are observed, for example, in the Sahara and in Eastern Siberia, where the amplitudes are even greater, because both factors play a role here: continental climate and high latitude, while in Sahara amplitude depends mainly on the continentality of the country. In addition, fluctuations also depend on the topographic nature of the area. To see how much this last factor plays a significant role in the change in amplitude, it is sufficient to consider temperature fluctuations in the Jurassic and in the valleys. In summer, as you know, the temperature decreases with height rather quickly, therefore, on lonely peaks, surrounded on all sides by cold air, the temperature is much lower than in valleys, which are strongly heated in summer. In winter, on the contrary, cold and dense layers of air are located in the valleys, and the temperature of the air rises with height to a certain limit, so that individual small peaks are sometimes like heat islands in winter, while in summer they are colder points. Consequently, the annual amplitude, or the difference between winter and summer temperatures, is greater in the valleys than in the mountains. The outskirts of the plateaus are in the same conditions as individual mountains: surrounded by cold air, they at the same time receive less heat compared to flat, flat areas, so that their amplitude cannot be significant. The conditions for heating the central parts of the plateaus are already different. Strongly heated in summer due to rarefied air, they radiate much less heat compared to isolated mountains, because they are surrounded by heated parts of the plateau, and not by cold air. Therefore, in summer the temperature on the plateaus can be very high, while in winter the plateaus lose a lot of heat by radiation due to the rarefaction of the air above them, and it is natural that very strong temperature fluctuations are observed here.

CHAPTERIIISHELLS OF THE EARTH

Topic 2 ATMOSPHERE

§thirty. DAILY CHANGE OF AIR TEMPERATURE

Remember what is the source of light and heat on Earth.

How is clear air heated?

HOW THE AIR HEATS. From the lessons of natural history, you know that transparent air transmits the sun's rays to the earth's surface and heats it up. It is the air that does not heat up with rays, but heats up from a heated surface. Therefore, the farther from the earth's surface, the colder it is. That is why when a plane is flying high above the ground, the air temperature is very low. At the upper boundary of the troposphere, it drops to -56 °C.

It has been established that after each kilometer of altitude, the air temperature drops by an average of 6 °C (Fig. 126). High in the mountains, the earth's surface receives more solar heat than at the foot. However, heat dissipates faster with height. Therefore, while climbing the mountains, you can notice that the air temperature gradually decreases. That is why snow and ice lie on the tops of high mountains.

HOW TO MEASURE THE AIR TEMPERATURE. Of course, everyone knows that air temperature is measured with a thermometer. However, it is worth remembering that a thermometer is incorrectly installed, for example, in the sun, it will show not the air temperature, but how many degrees the device itself has heated up. At meteorological stations, to obtain accurate data, the thermometer is placed in a special booth. Its walls are slatted. This allows air to freely enter the booth, together the grilles protect the thermometer of the wii. direct sunlight. The booth is installed at a height of 2 m from the ground. Thermometer readings are recorded every 3 hours.

Rice. 126. Air temperature change with height

Flying above the clouds

In 1862, two Englishmen flew in a balloon. At an altitude of 3 km, bypassing the clouds, the researchers were shivering from the cold. When the clouds disappeared and the sun came out, it got even colder. At the height of these 5 km, the water froze. It became difficult for people to breathe, it was noisy in their ears, and with a lack of strength, it was actually the axis. So slam the rarefied air on the body. At an altitude of 3 km, one of the survivors lost consciousness. At altitudes and 11 km it was -24°C (on Earth at that time the grass was green and flowers were blooming). Both daredevils were threatened with death. Therefore, they descended to Earth as quickly as possible.

Rice. 127. Graph of the daily course of air temperature

DAILY CHANGE OF TEMPERATURE. The sun's rays during the day heat the Earth unevenly (Fig. 128). At noon, when the sun is high above the horizon, the earth's surface heats up the most. However, high air temperatures are observed not at noon (at 12 o'clock), but two or three hours after noon (at 14-15 o'clock). This is because it takes time to transfer heat from the earth's surface. In the afternoon, despite the fact that the Sun is already descending to the horizon, the air continues to receive heat from the heated surface for another two hours. Then the surface gradually cools down, the air temperature decreases accordingly. The lowest temperatures are before sunrise. True, on some days such a daily temperature pattern may be disturbed.

Consequently, the reason for the change in air temperature during the day is a change in the illumination of the Earth's surface due to its rotation around its axis. A more visual representation of the change in temperature is given by the graphs of the daily course of air temperature (Fig. 127).

WHAT IS THE AMPLITUDE OF AIR TEMPERATURE VARIATION. The difference between the highest and lowest air temperatures is called the amplitude of the temperature fluctuation (A). There are daily, monthly, annual amplitudes.

For example, if the highest air temperature during the day was +25 °C, and +9 °C, then the amplitude of the fluctuations will be 16 °C (25 - 9 = 16) (Mat. 129). The nature of the earth's surface (it is called the underlying) affects the daily amplitudes of temperature fluctuations. For example, over the oceans, the amplitude is only 1-2 °C, over the steppes 15-0 °C, and in deserts it reaches 30 °C.

Rice. 129. Determination of the daily amplitude of fluctuations in air temperature

REMEMBER

The air is heated from the earth's surface; With altitude, its temperature drops by about 6 ° C for every kilometer of altitude.

The air temperature during the day changes due to changes in surface illumination (change of day and night).

The amplitude of temperature fluctuation is the difference between the highest and lowest air temperatures.

QUESTIONS AND TASKS

1. The air temperature at the earth's surface is +17 °C. Determine the temperature outside an aircraft flying at an altitude of 10 km.

2. Why is a thermometer installed in a special booth at meteorological stations?

3. Tell us how the air temperature changes during the day.

4. Calculate the daily amplitude of air fluctuations according to the following data (in ° C): -1.0, + 4, +5, +3, -2.

5. Think about why the highest daily air temperature is not observed at noon, when the Sun is high above the horizon.

PRACTICE 5 (Beginning. See pp. 133, 141.)

Topic: Solving problems on the change in air temperature with height.

1. The air temperature at the earth's surface is +25 °C. Determine the air temperature at the top of a mountain whose height is 1500 m.

2. The thermometer on the meteorological station, located on the top of the mountain, shows 16 ° C above zero. At the same time, the air temperature at its foot is +23.2 °C. Calculate the relative height of the mountain.

The daily course of air temperature is determined by the corresponding course of the temperature of the active surface. Heating and cooling of air depend on the thermal regime of the active surface. The heat absorbed by this surface partially spreads into the depths of the soil or reservoir, and the other part is given off to the adjacent layer of the atmosphere and then spreads to the overlying layers. In this case, there is some delay in the growth and decrease in air temperature compared to the change in soil temperature.

The minimum air temperature at a height of 2 m is observed before sunrise. As the sun rises above the horizon, the air temperature rises rapidly for 2-3 hours. Then the rise in temperature slows down. Its maximum occurs after 2-3 hours in the afternoon. Further, the temperature decreases - first slowly, and then more rapidly.

Over the seas and oceans, the maximum air temperature occurs 2-3 hours earlier than over the continents, and the amplitude of the daily variation of air temperature over large water bodies is greater than the amplitude of the temperature fluctuations of the water surface. This is explained by the fact that the absorption of solar radiation by air and its own radiation over the sea is much greater than over land, since over the sea the air contains more water vapor.

Features of the diurnal variation of air temperature are revealed by averaging the results of long-term observations. With this averaging, individual non-periodic violations of the daily temperature variation associated with the intrusions of cold and warm air masses are excluded. These intrusions distort the diurnal variation of temperature. For example, during the intrusion of a cold air mass during the day, the air temperature over some points sometimes drops, rather than rises. With the invasion of a warm mass at night, the temperature can rise.

With steady weather, the change in air temperature during the day is quite clearly expressed. But the amplitude of the daily variation of air temperature over land is always less than the amplitude of the daily variation of the temperature of the soil surface. The amplitude of the daily variation of air temperature depends on a number of factors.

The latitude of the place. As the latitude increases, the amplitude of the daily variation in air temperature decreases. The greatest amplitudes are observed in subtropical latitudes. On average, for a year, the considered amplitude is about 12°С in tropical regions, 8–9°С in temperate latitudes, 3–4°С near the Arctic Circle, and 1–2°С in the Arctic.

Season. In temperate latitudes, the smallest amplitudes are observed in winter, and the largest in summer. In spring they are somewhat larger than in autumn. The amplitude of the daily temperature variation depends not only on the daytime maximum, but also on the nighttime minimum, which is lower the longer the night. In temperate and high latitudes, during short summer nights, the temperature does not have time to drop to very low values, and therefore the amplitude here remains relatively small. In the polar regions, under the conditions of a round-the-clock polar day, the amplitude of the daily variation in air temperature is only about 1 °C. During the polar night, diurnal temperature fluctuations are almost not observed. In the Arctic, the largest amplitudes are observed in spring and autumn. On Dixon Island, the highest amplitude during these seasons averages 5--6 °C.

The greatest amplitudes of the diurnal variation of air temperature are observed in tropical latitudes, and here they hardly depend on the time of year. Thus, in tropical deserts, these amplitudes are 20–22 °С throughout the year.

The nature of the active surface. Above the water surface, the amplitude of the daily variation in air temperature is less than over land. Over the seas and oceans, they average 2--3°C. With distance from the coast to the depths of the mainland, the amplitudes increase to 20–22 °C. A similar, but weaker effect on the daily course of air temperature is exerted by inland water bodies and highly moistened surfaces (swamps, places with abundant vegetation). In dry steppes and deserts, the average annual amplitude of the daily variation of air temperature reaches 30 °C.

Cloudy. The amplitude of the daily variation of air temperature on clear days is greater than on cloudy days, since fluctuations in air temperature are directly dependent on fluctuations in the temperature of the active layer, which in turn are directly related to the number and nature of clouds.

Terrain relief. The relief of the area has a significant influence on the daily course of air temperature, which was first noticed by A. I. Voeikov. With concave relief forms (hollows, hollows, valleys), the air comes into contact with the largest area of ​​the underlying surface. Here the air stagnates during the day, and at night it cools over the slopes and flows to the bottom. As a result, both daytime heating and nighttime air cooling increase inside concave landforms compared to flat terrain. Thus, the amplitudes of diurnal temperature fluctuations in such a relief also increase. With convex landforms (mountains, hills, hills), the air comes into contact with the smallest area of ​​the underlying surface. The influence of the active surface on the air temperature decreases. Thus, the amplitudes of the daily variation of air temperature in depressions, hollows, and valleys are greater than over the plains, and over the latter they are greater than over the tops of mountains and hills.

Height above sea level. With an increase in altitude, the amplitude of the daily variation in air temperature decreases, and the moments of the onset of maxima and minima are shifted to a later time. The diurnal variation of temperature with an amplitude of 1–2°C is observed even at the height of the tropopause, but here it is already due to the absorption of solar radiation by ozone contained in the air.

The annual course of air temperature is determined, first of all, by the annual course of the temperature of the active surface. The amplitude of the annual cycle is the difference between the average monthly temperatures of the warmest and coldest months.

In the northern hemisphere on the continents, the maximum average air temperature is observed in July, the minimum in January. On the oceans and coasts of the continents, extreme temperatures occur somewhat later: maximum - in August, minimum - in February - March. On land, the amplitude of the annual variation in air temperature is much greater than above the water surface.

The latitude of the place has a great influence on the amplitude of the annual variation of air temperature. The smallest amplitude is observed in the equatorial zone. With an increase in the latitude of the place, the amplitude increases, reaching the highest values ​​in the polar latitudes. The amplitude of annual fluctuations in air temperature also depends on the height of the place above sea level. As the height increases, the amplitude decreases. Weather conditions have a great influence on the annual course of air temperature: fog, rain and mainly cloudiness. The absence of clouds in winter leads to a decrease in the average temperature of the coldest month, and in summer - to an increase in the average temperature of the warmest month.

The annual course of air temperature in different geographical areas is diverse. According to the magnitude of the amplitude and the time of onset of extreme temperatures, four types of annual variation in air temperature are distinguished.

• 1. Equatorial type. In the equatorial zone, two temperature maxima are observed per year - after the spring and autumn equinoxes, when the sun is at its zenith above the equator at noon, and two minimums - after the winter and summer solstices, when the sun is at its lowest altitude. The amplitudes of the annual variation are small here, which is explained by a small change in the heat inflow during the year. Over the oceans, the amplitudes are about 1 °C, and over the continents, 5–10 °C.
• 2. Type of temperate zone. In temperate latitudes, there is also an annual variation in temperature with a maximum after the summer and a minimum after the winter solstice. Over the continents of the northern hemisphere, the maximum average monthly temperature is observed in July, over the seas and coasts - in August. Annual amplitudes increase with latitude. Over the oceans and coasts, they average 10--15 ° C, over the continents 40--50 ° C, and at a latitude of 60 ° reach 60 ° C.
• 3. Polar type. The polar regions are characterized by long cold winters and relatively short cool summers. The annual amplitudes over the ocean and the coasts of the polar seas are 25–40 °C, and on land they exceed 65 °C. The maximum temperature is observed in August, the minimum - in January.

The considered types of annual variations in air temperature are identified from long-term data and represent regular periodic fluctuations. In some years, under the influence of intrusions of warm or cold masses, deviations from the above types occur. Frequent invasions of sea air masses on the mainland lead to a decrease in amplitude. Intrusions of continental air masses on the coasts of the seas and oceans increase their amplitude in these areas. Non-periodic temperature changes are mainly associated with the advection of air masses. For example, in temperate latitudes, significant non-periodic cooling occurs when cold air masses invade from the Arctic. At the same time, returns of cold are often noted in the spring. When tropical air masses invade temperate latitudes, heat returns are observed in autumn 8, p. 285 - 291.

General information about air temperature

Definition 1

The indicator of the thermal state of air recorded by measuring instruments is called temperature.

The sun's rays, falling on the spherical shape of the planet, heat it in different ways, because they come from different angles. The sun's rays do not heat the atmospheric air, while the earth's surface heats up very strongly and transfers thermal energy to the adjacent layers of air. Warm air becomes light and rises, where it mixes with cold air, giving off part of its thermal energy. Warm air cools with height and at a height of $10$ km its temperature becomes constant $-40$ degrees.

Definition 2

In the stratosphere, temperatures are shifting, and its indicators begin to rise. This phenomenon has been named temperature inversion.

Most of all, the surface of the earth heats up where the sun's rays fall at right angles - this is the area equator. The minimum amount of heat received polar and polar regions, because the angle of incidence of the sun's rays is sharp and the rays glide over the surface, and besides, they are also scattered by the atmosphere. As a result of this, we can say that the air temperature decreases from the equator to the poles of the planet.

An important role is played by the inclination of the earth's axis to the plane of the orbit and the time of year, which leads to uneven heating of the Northern and Southern hemispheres. Air temperature is not a constant indicator; it changes throughout the day anywhere in the world. On thematic climate maps, air temperature is shown by a special symbol, which is called isotherm.

Definition 3

Isotherms- these are lines connecting points on the earth's surface with the same temperature.

On the basis of isotherms, thermal belts are distinguished on the planet, going from the equator to the poles:

• Equatorial or hot belt;
• Two temperate belts;
• two cold zones.

Thus, the air temperature is greatly influenced by:

• Geographic latitude of the place;
• Heat transfer from low latitudes to high latitudes;
• Distribution of continents and oceans;
• Location of mountain ranges;
• Currents in the ocean.

Temperature change

The air temperature changes continuously throughout the day. The land heats up quickly during the day, and the air heats up from it, but with the onset of the night, the land also cools quickly, and after it the air cools. Therefore, it will be coolest in the predawn hours, and warmest in the afternoon.

The exchange of heat, mass and momentum between the individual layers of the atmosphere occurs constantly. The interaction of the atmosphere with the earth's surface is characterized by the same processes and is carried out in the following ways:

• Radiation path (air absorption of solar radiation);
• Thermal conduction path;
• Heat transfer by evaporation, condensation or crystallization of water vapor.

The air temperature even at the same latitude cannot be constant. On Earth, only in one climatic zone there is no daily temperature fluctuation - this is a hot or equatorial zone. Here, both night and day air temperatures will have the same value. On the coasts of large reservoirs and above their surface, the daily amplitude is also insignificant, but in the desert climate zone, the difference between day and night temperatures sometimes reaches $50-60$ degrees.

In temperate climatic zones, the maximum solar radiation occurs on the days of the summer solstices - in the Northern Hemisphere it is July month, and in the southern hemisphere - January. The reason for this lies not only in intense solar radiation, but also in the fact that the very heated surface of the planet gives off a huge amount of thermal energy.

Middle latitudes are characterized by higher annual amplitudes. Any place on the planet is characterized by its average and absolute air temperatures. The hottest place on earth is Libyan desert, where the absolute maximum is fixed - ($ +58 $ degrees), and the coldest place is the Russian station "East" in Antarctica - ($ -89.2 $ degrees). All average temperatures - average daily, average monthly, average annual - are arithmetic mean values ​​of several indicators of the thermometer. We already know that air temperature in the troposphere decreases with height, but in the surface layer its distribution can be different - it can increase, decrease or remain constant. The idea of ​​how air temperature is distributed with height gives vertical gradient temperature (VGT). Time of year, time of day, weather conditions affect the value of VGT. For example, the wind contributes to the mixing of air and at different heights its temperature levels off, which means that the WGT wind decreases. VGT sharply decreases if the soil is wet, the fallow field has more VGT than a densely sown field, because these surfaces have different temperature regimes.

The sign of the VGT indicates how the temperature changes with height, if it is less than zero, then the temperature increases with height. And, conversely, if the sign is greater than zero, the temperature will decrease with distance from the surface and will remain unchanged at VGT = 0. Such a distribution of temperature with height is called inversions.

Inversions can be:

• Radiation (radiation cooling of the surface);
• Advective (formed when warm air moves onto a cold surface).

There are four types of annual temperature variation based on the average long-term amplitude and time of onset of extreme temperatures:

• Equatorial type - there are two maxima and two minima;
• Tropical type (maximum and minimum observed after the solstices);
• Moderate type (maximum and minimum are observed after the solstices);
• Polar type (minimum temperature during the polar night);

The height of a place above sea level also affects the annual course of air temperature. The annual amplitude decreases with height. Air temperature is measured by specialists at meteorological stations.