Thermal regime of the earth's surface and air. Thermal regime of the atmosphere

Thermal regime of the earth's surface. Solar radiation coming to the Earth heats mainly its surface. The thermal state of the earth's surface is therefore the main source of heating and cooling of the lower layers of the atmosphere.

The conditions for heating the earth's surface depend on its physical properties. First of all, there are sharp differences in the heating of the surface of land and water. On land, heat propagates in depth mainly by inefficient molecular heat conduction. In this regard, daily temperature fluctuations on the land surface extend only to a depth of 1 m, and annual - up to 10-20 m. In the water surface, the temperature spreads in depth mainly by mixing the water masses; molecular thermal conductivity is negligible. In addition, deeper penetration of radiation into water plays a role here, as well as a higher heat capacity of water compared to land. Therefore, daily and annual temperature fluctuations propagate in water to a greater depth than on land: daily - by tens of meters, annual - by hundreds of meters. As a result, heat entering and leaving the earth's surface is distributed in a thinner layer of land than the water surface. This means that the daily and annual temperature fluctuations on the land surface should be much greater than on the water surface. Since air is heated from the earth's surface, then with the same value of solar radiation in summer and during the day, the air temperature over land will be higher than over the sea, and vice versa in winter and at night.

The heterogeneity of the land surface also affects the conditions of its heating. Vegetation during the day prevents the strong heating of the soil, and at night reduces its cooling. Snow cover protects the soil from excessive heat loss in winter. Diurnal temperature amplitudes under vegetation will thus be reduced. The combined effect of vegetation cover in summer and snowy winter reduces the annual temperature amplitude compared to the bare surface.

The extreme limits of land surface temperature fluctuations are as follows. In the deserts of the subtropics, the temperature can rise to +80°, on the snowy surface of Antarctica it can drop to -90°.

On the water surface, the moments of the onset of the maximum and minimum temperature in the daily and annual course are shifted compared to land. The daily maximum occurs around 15-16 hour, at least 2-3 hour after sunrise. The annual maximum temperature of the ocean surface occurs in the northern hemisphere in August, the annual minimum - in February. The maximum observed temperature of the ocean surface is about 27 °, the surface of the inland water basins 45°; the minimum temperature is -2 and -13°, respectively.

Thermal regime of the atmosphere.The change in air temperature is determined by several reasons: solar and terrestrial radiation, molecular thermal conductivity, evaporation and condensation of water vapor, adiabatic changes and heat transfer with air mass.

For the lower layers of the atmosphere, the direct absorption of solar radiation is of little importance; their absorption of long-wave terrestrial radiation is much more significant. Molecular thermal conductivity heats the air immediately adjacent to the earth's surface. When water evaporates, heat is expended, and consequently, the air cools; when water vapor condenses, heat is released, and the air heats up.

has a great influence on the distribution of air temperature adiabatic change her, i.e., a change in temperature without heat exchange with the surrounding air. Rising air expands; work is expended on expansion, which leads to a decrease in temperature. When the air is lowered, the reverse process occurs. Dry or non-saturated air cools adiabatically every 100 m lift by 1°. Air saturated with water vapor cools down by a smaller amount (on average by 0.6 per 100 m rise), since in this case condensation of water vapor occurs, which is accompanied by the release of heat.

The transfer of heat together with the mass of air has a particularly great influence on the thermal regime of the atmosphere. As a result general circulation atmosphere, both vertical and horizontal movement of air masses occurs all the time, capturing the entire thickness of the troposphere and penetrating even into the lower stratosphere. The first is called convection second - advection. These are the main processes that determine the actual distribution of air temperature over land and sea surfaces and at different altitudes. Adiabatic processes are only a physical consequence of temperature changes in air moving according to the laws of atmospheric circulation. The role of heat transfer together with the mass of air can be judged by the fact that the amount of heat received by air as a result of convection is 4,000 times greater than the heat received by radiation from the earth's surface, and 500,000 times more

than the heat generated by molecular heat conduction. Based on the equation of state for gases, the temperature should decrease with height. However, under special conditions of heating and cooling the air, the temperature may increase with altitude. Such a phenomenon is called temperature inversion. An inversion occurs when the earth's surface is strongly cooled as a result of radiation, when cold air flows into depressions, when air moves downward in a free atmosphere, i.e. above the level of friction. Temperature inversions play big role in atmospheric circulation and affect weather and climate. Daily and annual course air temperatures depend on the course of solar radiation. However, the onset of the temperature maximum and minimum is delayed in relation to the maximum and minimum of solar radiation. After noon, the influx of heat from the Sun begins to decrease, but the air temperature continues to rise for some time, because the decrease in solar radiation is replenished by heat radiation from the earth's surface. At night, the decrease in temperature continues until sunrise due to terrestrial heat radiation (Fig. 11). A similar pattern applies to the annual temperature variation. The amplitude of fluctuations in air temperature is less than that of the earth's surface, and with distance from the surface, the amplitude of fluctuations naturally decreases, and the moments of maximum and minimum temperature are more and more late. The magnitude of diurnal temperature fluctuations decreases with increasing latitude and with increasing cloudiness and precipitation. Over the water surface, the amplitude is much less than over land.

If the earth's surface were homogeneous, and the atmosphere and hydrosphere were stationary, then the distribution of heat over the surface would be determined only by the influx of solar radiation, and the air temperature would gradually decrease from the equator to the poles, remaining the same at each parallel. This temperature is called solar.

Actual temperatures depend on the nature of the surface and interlatitudinal heat exchange and differ significantly from solar temperatures. different latitudes in degrees are shown in Table. one.

A visual representation of the distribution of air temperature on the earth's surface is shown by maps of isotherms - lines connecting points with the same temperatures (Fig. 12, 13).

As can be seen from the maps, the isotherms strongly deviate from parallels, which is explained by a number of reasons: unequal heating of land and sea, the presence of warm and cold sea currents, the influence of the general circulation of the atmosphere (for example, westerly transport to temperate latitudes), the influence of the relief (barrier effect on the air movement of mountain systems, the accumulation of cold air in intermountain basins, etc.), the magnitude of the albedo (for example, the large albedo of the snow-ice surface of Antarctica and Greenland).

The absolute maximum air temperature on Earth is observed in Africa (Tripoli) - about +58°. Absolute minimum noted in Antarctica (-88°).

Based on the distribution of isotherms, thermal belts on the earth's surface. The tropics and polar circles, limiting the belts with a sharp change in the illumination regime (see Chap. 1), are, in the first approximation, the boundaries of the change in the thermal regime. Since the actual air temperatures differ from solar ones, characteristic isotherms are taken as thermal zones. Such isotherms are: annual 20° (border of sharply pronounced seasons of the year and small temperature amplitude), the warmest month 10° (forest distribution boundary) and the warmest month 0° (border of eternal frost).

Between the annual isotherms of 20° of both hemispheres there is a hot zone, between the annual isotherm of 20° and the isotherm of the

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Directly from the sun's rays, the earth's surface is heated, and already from it - the atmosphere. The surface that receives and gives off heat is called active surface . In the temperature regime of the surface, the daily and annual temperature variations are distinguished. The diurnal variation of surface temperatures – change in surface temperature during the day. The daily course of land surface temperatures (dry and devoid of vegetation) is characterized by one maximum at about 13:00 and one minimum before sunrise. Daytime maxima of land surface temperature can reach 80 0 C in the subtropics and about 60 0 C in temperate latitudes.

The difference between the maximum and minimum daily surface temperature is called daily temperature range. The daily temperature amplitude can reach 40 0 ​​С in summer, the smallest amplitude of daily temperatures in winter - up to 10 0 С.

Annual variation of surface temperature- change in the average monthly surface temperature during the year, due to the course of solar radiation and depends on the latitude of the place. In temperate latitudes, the maximum land surface temperatures are observed in July, the minimum - in January; on the ocean, the highs and lows are a month late.

Annual amplitude of surface temperatures equal to the difference between the maximum and minimum average monthly temperatures; increases with increasing latitude of the place, which is explained by the increase in fluctuations in the magnitude of solar radiation. The annual temperature amplitude reaches its greatest values ​​on the continents; much less on the oceans and seashores. The smallest annual temperature amplitude is observed in the equatorial latitudes (2-3 0), the largest - in the subarctic latitudes on the continents (more than 60 0).

Thermal regime of the atmosphere. Atmospheric air is slightly heated by direct sunlight. Because the air shell freely passes the sun's rays. The atmosphere is heated by the underlying surface. Heat is transferred to the atmosphere by convection, advection and condensation of water vapor. The layers of air, heated by the soil, become lighter and rise upwards, while the colder, therefore, heavier air descends. As a result of thermal convection heating of high layers of air. The second heat transfer process is advection– horizontal air transfer. The role of advection is to transfer heat from low to high latitudes; in the winter season, heat is transferred from the oceans to the continents. Water vapor condensation- an important process that transfers heat to high layers of the atmosphere - during evaporation, heat is taken from the evaporating surface, during condensation in the atmosphere, this heat is released.

Temperature decreases with height. The change in air temperature per unit distance is called vertical temperature gradient on average, it is 0.6 0 per 100 m. At the same time, the course of this decrease in different layers of the troposphere is different: 0.3-0.4 0 up to a height of 1.5 km; 0.5-0.6 - between heights of 1.5-6 km; 0.65-0.75 - from 6 to 9 km and 0.5-0.2 - from 9 to 12 km. In the surface layer (2 m thick), the gradients, when converted to 100 m, are hundreds of degrees. In rising air, the temperature changes adiabatically. adiabatic process - the process of changing the air temperature during its vertical movement without heat exchange with the environment (in one mass, without heat exchange with other media).

Exceptions are often observed in the described vertical temperature distribution. It happens that the upper layers of air are warmer than the lower ones adjacent to the ground. This phenomenon is called temperature inversion (increase in temperature with altitude) . Most often, an inversion is a consequence of a strong cooling of the surface layer of air caused by a strong cooling of the earth's surface on clear, quiet nights, mainly in winter. With a rugged relief, cold air masses slowly flow down the slopes and stagnate in basins, depressions, etc. Inversions can also form when air masses move from warm to cold regions, since when heated air flows onto a cold underlying surface, its lower layers noticeably cool (compression inversion).

Its value and change on the surface that is directly heated by the sun's rays. When heated, this surface transfers heat (in the long-wave range) both to the underlying layers and to the atmosphere. The surface itself is called active surface.

The maximum value of all elements of the heat balance is observed in the near noon hours. The exception is the maximum heat exchange in the soil, which falls on the morning hours. The maximum amplitudes of the diurnal variation of the heat balance components are observed in summer, and the minimum ones in winter.

In the diurnal course of surface temperature, dry and devoid of vegetation, on a clear day, the maximum occurs after 14 hours, and the minimum is around sunrise. Cloudiness can disturb the diurnal variation of temperature, causing a shift in the maximum and minimum. Humidity and surface vegetation have a great influence on the course of temperature.

Daily surface temperature maximums can be +80 o C or more. Daily fluctuations reach 40 o. The values ​​of extreme values ​​and temperature amplitudes depend on the latitude of the place, season, cloudiness, thermal properties of the surface, its color, roughness, nature of the vegetation cover, slope orientation (exposure).

The spread of heat from the active surface depends on the composition of the underlying substrate, and will be determined by its heat capacity and thermal conductivity. On the surface of the continents, the underlying substrate is soil, in the oceans (seas) - water.

Soils in general have a lower heat capacity than water and a higher thermal conductivity. Therefore, they heat up and cool down faster than water.

Time is spent on the transfer of heat from layer to layer, and the moments of the onset of maximum and minimum temperature values ​​during the day are delayed by every 10 cm by about 3 hours. The deeper the layer, the less heat it receives and the weaker the temperature fluctuations in it. The amplitude of diurnal temperature fluctuations with depth decreases by 2 times for every 15 cm. At an average depth of about 1 m, the daily fluctuations in soil temperature "fade out". The layer where they stop is called layer of constant daily temperature.

The longer the period of temperature fluctuations, the deeper they spread. Thus, in the middle latitudes, the layer of constant annual temperature is at a depth of 19–20 m, in high latitudes, at a depth of 25 m, and in tropical latitudes, where the annual temperature amplitudes are small, at a depth of 5–10 m. years are delayed by an average of 20-30 days per meter.

The temperature in the layer of constant annual temperature is close to the average annual air temperature above the surface.

Soil is a component of the climate system, which is the most active accumulator solar heat arriving at the earth's surface.

The daily course of the underlying surface temperature has one maximum and one minimum. The minimum occurs around sunrise, the maximum occurs in the afternoon. The phase of the diurnal cycle and its daily amplitude depend on the season, the state of the underlying surface, the amount and precipitation, and also, on the location of the stations, the type of soil and its mechanical composition.

According to the mechanical composition, soils are divided into sandy, sandy and loamy, differing in heat capacity, thermal diffusivity and genetic properties(particularly the color). Dark soils absorb more solar radiation and therefore warm up more than light soils. Sandy and sandy loamy soils, characterized by a smaller, warmer than loamy.

The annual course of the underlying surface temperature shows a simple periodicity with a minimum in winter and a maximum in summer. In most of the territory of Russia, the highest soil temperature is observed in July, on Far East in the coastal strip of the Sea of ​​Okhotsk, on and - in July - August, in the south of Primorsky Krai - in August.

The maximum temperatures of the underlying surface during most of the year characterize the extreme thermal state of the soil, and only for the coldest months - the surface.

The weather conditions favorable for the underlying surface to reach maximum temperatures are: cloudy weather, when the influx of solar radiation is maximum; low wind speeds or calm, since an increase in wind speed increases the evaporation of moisture from the soil; a small amount of precipitation, since dry soil is characterized by lower heat and thermal diffusivity. In addition, in dry soil there is less heat consumption for evaporation. Thus, absolute temperature maxima are usually observed during the clearest sunny days on dry soil and usually in the afternoon.

The geographical distribution of averages from the absolute annual maxima of the underlying surface temperature is similar to the distribution of isogeotherms of the average monthly temperatures of the soil surface in summer months. Isogeotherms are mainly latitudinal. The influence of the seas on the temperature of the soil surface is manifested in the fact that on the western coast of Japan and, on Sakhalin and Kamchatka, the latitudinal direction of the isogeoterms is disturbed and becomes close to the meridional (repeats the outlines of the coastline). In the European part of Russia, the values ​​of the average of the absolute annual maxima of the underlying surface temperature vary from 30–35°С on the coast northern seas up to 60–62°С in the south Rostov region, in Krasnodar and Stavropol Territory, in the Republic of Kalmykia and the Republic of Dagestan. In the area, the average of the absolute annual maxima of soil surface temperature is 3–5°C lower than in the nearby flat areas, which is associated with the influence of elevations on the increase in precipitation in the area and soil moisture. Plain territories, closed by hills from the prevailing winds, are characterized by a reduced amount of precipitation and lower wind speeds, and, consequently, increased values ​​of extreme temperatures of the soil surface.

The most rapid increase in extreme temperatures from north to south occurs in the zone of transition from the forest and zones to the zone, which is associated with a decrease in precipitation in steppe zone and changes in soil composition. In the south, with a general low level of moisture content in the soil, the same changes in soil moisture correspond to more significant differences in the temperature of soils that differ in mechanical composition.

There is also a sharp decrease in the average of the absolute annual maxima of the temperature of the underlying surface from south to north in the northern regions of the European part of Russia, during the transition from the forest zone to zones and tundra - areas of excessive moisture. The northern regions of the European part of Russia, due to active cyclonic activity, among other things, differ from the southern regions in an increased amount of cloudiness, which sharply reduces the arrival of solar radiation to the earth's surface.

In the Asian part of Russia, the lowest average absolute maxima occur on the islands and in the north (12–19°C). As we move southward, there is an increase in extreme temperatures, and in the north of the European and Asian parts of Russia, this increase occurs more sharply than in the rest of the territory. In areas with a minimum amount of precipitation (for example, the areas between the Lena and Aldan rivers), pockets of increased extreme temperatures are distinguished. Since the regions are very complex, the extreme temperatures of the soil surface for stations located in various forms of relief (mountainous regions, basins, lowlands, valleys of large Siberian rivers) differ greatly. The average values ​​of the absolute annual maximum temperatures of the underlying surface reach the highest values ​​in the south of the Asian part of Russia (except for coastal areas). In the south of Primorsky Krai, the average of absolute annual maxima is lower than in continental regions located at the same latitude. Here their values ​​reach 55–59°С.

The minimum temperatures of the underlying surface are also observed under quite specific conditions: on the coldest nights, at hours close to sunrise, during anticyclonic weather conditions, when low cloudiness favors maximum effective radiation.

The distribution of average isogeotherms from the absolute annual minima of the underlying surface temperature is similar to the distribution of isotherms of minimum air temperatures. In most of the territory of Russia, except for the southern and northern regions, the average isogeotherms of the absolute annual minimum temperatures of the underlying surface take on a meridional orientation (decreasing from west to east). In the European part of Russia, the average of the absolute annual minimum temperatures of the underlying surface varies from -25°C in the western and southern regions to -40 ... -45°C in the eastern and, especially, northeastern regions (Timan Ridge and Bolshezemelskaya tundra). The highest mean values ​​of the absolute annual temperature minima (–16…–17°С) take place in Black Sea coast. In most of the Asian part of Russia, the average of the absolute annual minimums vary within -45 ... -55 ° С. Such an insignificant and fairly uniform distribution of temperature over a vast territory is associated with the uniformity of the conditions for the formation of minimum temperatures in areas subject to the influence of the Siberian.

In the districts Eastern Siberia with a complex relief, especially in the Republic of Sakha (Yakutia), along with radiation factors, the relief features have a significant impact on the decrease in minimum temperatures. Here, in the difficult conditions of a mountainous country in depressions and basins, especially favorable conditions are created for cooling the underlying surface. The Republic of Sakha (Yakutia) has the lowest average values ​​of the absolute annual minimums of the underlying surface temperature in Russia (up to –57…–60°С).

On the coast of the Arctic seas, due to the development of active winter cyclonic activity, the minimum temperatures are higher than in the interior. The isogeotherms have an almost latitudinal direction, and the decrease in the average of the absolute annual minima from north to south occurs rather quickly.

On the coast, the isogeotherms repeat the outlines of the shores. The influence of the Aleutian minimum is manifested in the increase in the average of the absolute annual minimums in the coastal zone compared to the inland areas, especially on the southern coast of Primorsky Krai and on Sakhalin. The average of the absolute annual minimums here is –25…–30°C.

The freezing of the soil depends on the magnitude of negative air temperatures in the cold season. The most important factor preventing soil freezing is the presence of snow cover. Its characteristics such as formation time, power, duration of occurrence determine the depth of soil freezing. The late establishment of snow cover contributes to greater freezing of the soil, since in the first half of winter the intensity of soil freezing is greatest and, conversely, the early establishment of snow cover prevents significant freezing of the soil. The influence of the thickness of the snow cover is most pronounced in areas with low air temperatures.

At the same depth of freezing depends on the type of soil, its mechanical composition and humidity.

For example, in the northern regions of Western Siberia, with low and thick snow cover, the depth of soil freezing is less than in more southern and warmer regions with small. A peculiar picture takes place in areas with unstable snow cover (southern regions of the European part of Russia), where it can contribute to an increase in the depth of soil freezing. This is due to the fact that with frequent changes of frost and thaw, an ice crust forms on the surface of a thin snow cover, the thermal conductivity coefficient of which is several times greater than the thermal conductivity of snow and water. The soil in the presence of such a crust cools and freezes much faster. The presence of vegetation cover contributes to a decrease in the depth of soil freezing, as it retains and accumulates snow.

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1 THERMAL REGIME OF THE ATMOSPHERE AND THE EARTH'S SURFACE

2 Heat balance of the earth's surface The total radiation and the counter radiation of the atmosphere enter the earth's surface. They are absorbed by the surface, that is, they go to heat the upper layers of soil and water. At the same time, the earth's surface itself radiates and loses heat in the process.

3 Earth surface (active surface, underlying surface) i.e. the surface of soil or water (vegetation, snow, ice cover), continuously different ways gains and loses heat. Through the earth's surface, heat is transferred up into the atmosphere and down into the soil or water. In any period of time, the same amount of heat goes up and down from the earth's surface as it receives from above and below during this time. If it were otherwise, the law of conservation of energy would not be fulfilled: it would be necessary to assume that energy arises or disappears on the earth's surface. Algebraic sum of all incomes and expenses of heat on the earth's surface should be equal to zero. This is expressed by the equation of the heat balance of the earth's surface.

4 heat balance equation To write the heat balance equation, firstly, we combine the absorbed radiation Q (1- A) and the effective radiation Eef = Ez - Ea into a radiation balance: B=S +D R + Ea Ez or B= Q (1 - A) - Eef

5 Radiation balance of the earth's surface - This is the difference between absorbed radiation (total radiation minus reflected) and effective radiation (radiation of the earth's surface minus counterradiation) B=S +D R + Ea Ez B=Q(1-A)-Eef 0 Therefore V= - Eeff

6 1) The arrival of heat from the air or its release into the air by thermal conductivity, we denote P 2) The same income or consumption by heat exchange with deeper layers of soil or water, we will call A. 3) The loss of heat during evaporation or its arrival during condensation on the earth's surface, we denote LE where L is the specific heat of vaporization and E is evaporation/condensation (mass of water). Then the equation for the heat balance of the earth's surface will be written as follows: B \u003d P + A + LE The heat balance equation refers to the unit area of ​​​​the active surface All its members are energy flows They have the dimension of W / m 2

7, the meaning of the equation is that the radiative balance on the earth's surface is balanced by non-radiative heat transfer. The equation is valid for any period of time, including for many years.

8 Components of the heat balance of the Earth-atmosphere system Received from the sun Released by the earth's surface

9 Heat balance options Q Radiation balance LE Evaporation heat loss H Turbulent heat flux from (into) the atmosphere from the underlying surface G -- Heat flux into (from) the depth of the soil

10 Arrival and consumption B=Q(1-A)-Eef B= P+A+LE Q(1-A)- The flux of solar radiation, partially reflecting, penetrates deep into the active layer to different depths and always heats it Effective radiation usually cools the surface Eeff Evaporation also always cools the surface LE The flow of heat into the atmosphere Р cools the surface during the day when it is hotter than the air, but warms it at night when the atmosphere is warmer than the earth's surface. Heat flow into the soil A, removes excess heat during the day (cools the surface), but brings the missing heat from the depths at night

11 The average annual temperature of the earth's surface and the active layer varies little from year to year From day to day and from year to year, the average temperature of the active layer and the earth's surface varies little in any place. This means that during the day, almost as much heat enters the depths of the soil or water during the day as it leaves it at night. But still, during the summer days, the heat goes down a little more than it comes from below. Therefore, the layers of soil and water, and their surface, are heated day by day. In winter, the reverse process occurs. These seasonal changes in the heat input and output in soil and water are almost balanced over the year, and the average annual temperature of the earth's surface and the active layer varies little from year to year.

12 The underlying surface is the earth's surface that interacts directly with the atmosphere.

13 Active surface Types of heat exchange of the active surface This is the surface of soil, vegetation and any other type of land and ocean surface (water), which absorbs and gives off heat. It regulates the thermal regime of the body itself and the adjacent air layer (surface layer)

14 Approximate values ​​of the parameters of the thermal properties of the active layer of the Earth Substance Density Kg / m 3 Heat capacity J / (kg K) Thermal conductivity W / (m K) air 1.02 water, 63 ice, 5 snow, 11 wood, 0 sand, 25 rock, 0

15 How the earth warms up: thermal conductivity is one of the types of heat transfer

16 Mechanism of heat conduction (transfer of heat deep into bodies) Heat conduction is one of the types of heat transfer from more heated parts of the body to less heated ones, leading to temperature equalization. At the same time, energy is transferred in the body from particles (molecules, atoms, electrons) with higher energy to particles with lower energy. flow q is proportional to grad T, that is, where λ is the thermal conductivity, or simply thermal conductivity, does not depend on grad T. λ depends on state of aggregation substance (see table), its atomic and molecular structure, temperature and pressure, composition (in the case of a mixture or solution), etc. The heat flux into the soil In the heat balance equation, this is A G T c z

17 The transfer of heat to the soil obeys the laws of Fourier thermal conductivity (1 and 2) 1) The period of temperature fluctuation does not change with depth 2) The amplitude of fluctuation decays exponentially with depth

18 The spread of heat into the soil The greater the density and moisture of the soil, the better it conducts heat, the faster it spreads to the depth and the deeper the temperature fluctuations penetrate. But, regardless of the type of soil, the period of temperature fluctuations does not change with depth. This means that not only on the surface, but also at depths, there remains a daily course with a period of 24 hours between each two successive maximums or minimums, and an annual course with a period of 12 months.

19 Formation of temperature in the upper soil layer (What cranked thermometers show) The amplitude of fluctuations decreases exponentially. Below a certain depth (about cm cm), the temperature hardly changes during the day.

20 Daily and annual variation of soil surface temperature The temperature on the soil surface has a daily variation: The minimum is observed approximately half an hour after sunrise. By this time, the radiation balance of the soil surface becomes equal to zero; the heat transfer from the upper soil layer by effective radiation is balanced by the increased influx of total radiation. The non-radiative heat exchange at this time is negligible. Then the temperature on the soil surface rises up to hours, when it reaches a maximum in the daily course. After that, the temperature starts to drop. The radiation balance in the afternoon remains positive; however, during the daytime heat is released from the upper soil layer to the atmosphere not only through effective radiation, but also through increased thermal conductivity, as well as increased evaporation of water. The transfer of heat into the depth of the soil also continues. Therefore, the temperature on the soil surface drops from the hours to the morning low.

21 Daily variation of temperature in the soil at different depths, the amplitudes of fluctuations decrease with depth. So, if on the surface the daily amplitude is 30, and at a depth of 20 cm - 5, then at a depth of 40 cm it will already be less than 1. At some relatively shallow depth, the daily amplitude decreases to zero. At this depth (about cm), a layer of constant daily temperature begins. Pavlovsk, May. The amplitude of annual temperature fluctuations decreases with depth according to the same law. However, annual fluctuations propagate to a greater depth, which is quite understandable: there is more time for their propagation. The amplitudes of annual fluctuations decrease to zero at a depth of about 30 m in the polar latitudes, about 10 m in the middle latitudes, and about 10 m in the tropics (where the annual amplitudes are also lower on the soil surface than in the middle latitudes). At these depths begins, a layer of constant annual temperature. The diurnal cycle in the soil attenuates with depth in amplitude and lags in phase depending on soil moisture: the maximum occurs in the evening on land and at night on the water (the same is true for the minimum in the morning and afternoon)

22 Fourier heat conduction laws (3) 3) The oscillation phase delay increases linearly with depth. the time of the onset of the temperature maximum shifts relative to the higher layers by several hours (towards evening and even night)

23 The fourth Fourier law The depths of the layers of constant daily and annual temperature are related to each other as the square roots of the periods of oscillations, i.e. as 1: 365. This means that the depth at which the annual oscillations decay is 19 times greater than the depth where the diurnal fluctuations are damped. And this law, like the rest of Fourier's laws, is quite well confirmed by observations.

24 Formation of temperature in the entire active layer of the soil (What is shown by exhaust thermometers) 1. The period of temperature fluctuations does not change with depth 2. Below a certain depth, the temperature does not change over the year. 3. Depths of propagation of annual fluctuations are approximately 19 times greater than daily fluctuations

25 Penetration of temperature fluctuations deep into the soil in accordance with the thermal conductivity model

26 . The average daily temperature variation on the soil surface (P) and in the air at a height of 2 m (V). Pavlovsk, June. The maximum temperatures on the soil surface are usually higher than in the air at the height of the meteorological booth. This is understandable: during the day, solar radiation primarily heats the soil, and already the air heats up from it.

27 annual course of soil temperature The temperature of the soil surface, of course, also changes in the annual course. In tropical latitudes, its annual amplitude, i.e., the difference in long-term average temperatures of the warmest and coldest months of the year, is small and increases with latitude. In the northern hemisphere at latitude 10 it is about 3, at latitude 30 about 10, at latitude 50 it averages about 25.

28 Temperature fluctuations in the soil attenuate with depth in amplitude and lag in phase, the maximum shifts to autumn, and the minimum to spring Annual maxima and minima are delayed by days for each meter of depth. Annual variation of temperature in the soil at different depths from 3 to 753 cm in Kaliningrad. In tropical latitudes, the annual amplitude, i.e., the difference in long-term average temperatures of the warmest and coldest months of the year, is small and increases with latitude. In the northern hemisphere at latitude 10 it is about 3, at latitude 30 about 10, at latitude 50 it averages about 25.

29 Thermal isopleth method Visually represents all the features of temperature variation both in time and with depth (in one point) Example of annual variation and daily variation Isoplets of annual temperature variation in soil in Tbilisi

30 Daily course of air temperature of the surface layer The air temperature changes in the daily course following the temperature of the earth's surface. Since the air is heated and cooled from the earth's surface, the amplitude of the daily temperature variation in the meteorological booth is less than on the soil surface, on average by about one third. The rise in air temperature begins with the rise in soil temperature (15 minutes later) in the morning, after sunrise. In hours, the temperature of the soil, as we know, begins to drop. In hours it equalizes with the air temperature; from that time on, with a further drop in soil temperature, the air temperature also begins to fall. Thus, the minimum in the daily course of air temperature near the earth's surface falls on the time shortly after sunrise, and the maximum at hours.

32 Differences in the thermal regime of soil and water bodies There are sharp differences in the heating and thermal characteristics of the surface layers of soil and the upper layers of water bodies. In soil, heat is distributed vertically by molecular heat conduction, and in lightly moving water also by turbulent mixing of water layers, which is much more efficient. Turbulence in water bodies is primarily due to waves and currents. But at night and in the cold season, thermal convection also joins this kind of turbulence: water cooled on the surface sinks down due to increased density and is replaced by more warm water from the lower layers.

33 Features of the temperature of water bodies associated with large coefficients of turbulent heat transfer Daily and annual fluctuations in water penetrate to much greater depths than in soil Temperature amplitudes are much smaller and almost the same in the UML of lakes and seas Heat fluxes in the active water layer are many times in soil

34 Daily and annual fluctuations As a result, daily fluctuations in water temperature extend to a depth of about tens of meters, and in the soil to less than one meter. Annual fluctuations in temperature in water extend to a depth of hundreds of meters, and in soil only to m. So, the heat that comes to the surface of the water during the day and summer penetrates to a considerable depth and heats up a large thickness of water. The temperature of the upper layer and the surface of the water itself rises little at the same time. In the soil, the incoming heat is distributed in a thin upper layer, which is thus strongly heated. Heat exchange with deeper layers in the heat balance equation "A" for water is much greater than for soil, and the heat flux into the atmosphere "P" (turbulence) is correspondingly less. At night and in winter, water loses heat from the surface layer, but instead of it comes the accumulated heat from the underlying layers. Therefore, the temperature at the surface of the water decreases slowly. On the soil surface, the temperature drops rapidly during heat release: the heat accumulated in the thin upper layer quickly leaves it without being replenished from below.

35 Maps of turbulent heat transfer of the atmosphere and the underlying surface were obtained

36 In the oceans and seas, evaporation also plays a role in the mixing of layers and the associated heat transfer. With significant evaporation from the sea surface, the upper layer of water becomes more salty and dense, as a result of which the water sinks from the surface to the depths. In addition, radiation penetrates deeper into water compared to soil. Finally, the heat capacity of water is large in comparison with soil, and the same amount of heat heats a mass of water to a lower temperature than the same mass of soil. HEAT CAPACITY - The amount of heat absorbed by a body when heated by 1 degree (Celsius) or given off when cooled by 1 degree (Celsius) or the ability of a material to accumulate thermal energy.

37 Due to these differences in the distribution of heat: 1. during the warm season, water accumulates in a sufficiently powerful layer of water a large number of heat released into the atmosphere during the cold season. 2. during the warm season, the soil gives off at night most of the heat that it receives during the day, and accumulates little of it by winter. As a result of these differences, the air temperature over the sea is lower in summer and higher in winter than over land. In the middle latitudes, during the warm half of the year, 1.5-3 kcal of heat is accumulated in the soil per square centimeter of surface. In cold weather, the soil gives off this heat to the atmosphere. The value of ±1.5 3 kcal / cm 2 per year is the annual heat cycle of the soil.

38 The amplitudes of the annual temperature variation determine the continental climate or nautical map amplitudes of the annual temperature variation near the Earth's surface

39 The position of the place relative to the coastline significantly affects the regime of temperature, humidity, cloudiness, precipitation and determines the degree of continentality of the climate.

40 Climate continentality Climate continentality - totality characteristic features climate, determined by the impact of the mainland on the processes of climate formation. In a climate over the sea (marine climate), small annual air temperature amplitudes are observed in comparison with the continental climate over land with large annual temperature amplitudes.

41 The annual variation of air temperature at latitude 62 N: in the Faroe Islands and Yakutsk reflects the geographical position of these points: in the first case - near the western coast of Europe, in the second - in the eastern part of Asia

42 Average annual amplitude in Torshavn 8, in Yakutsk 62 C. On the continent of Eurasia, an increase in the annual amplitude in the direction from west to east is observed.

43 Eurasia - the continent with the greatest distribution continental climate This type of climate is typical for the interior regions of the continents. The continental climate is dominant in a significant part of the territory of Russia, Ukraine, Central Asia(Kazakhstan, Uzbekistan, Tajikistan), Inner China, Mongolia, inner regions of the USA and Canada. The continental climate leads to the formation of steppes and deserts, since most of the moisture of the seas and oceans does not reach the inland regions.

44 continentality index is a numerical characteristic of climate continentality. There are a number of options for I K, which are based on one or another function of the annual amplitude of air temperature A: according to Gorchinsky, according to Konrad, according to Zenker, according to Khromov. There are indices built on other grounds. For example, the ratio of the frequency of occurrence of continental air masses to the frequency of sea air masses has been proposed as an IC. L. G. Polozova proposed to characterize the continentality separately for January and July in relation to the greatest continentality at a given latitude; this latter is determined from temperature anomalies. Η. Η. Ivanov proposed I.K. as a function of latitude, annual and daily temperature amplitudes, and humidity deficit in the driest month.

45 continentality index The magnitude of the annual amplitude of air temperature depends on the geographical latitude. At low latitudes, annual temperature amplitudes are smaller compared to high latitudes. This provision leads to the need to exclude the influence of latitude on the annual amplitude. For this, various indicators of climate continentality are proposed, represented by a function of the annual temperature amplitude and latitude. Formula L. Gorchinsky where A is the annual temperature amplitude. The average continentality over the ocean is zero, and for Verkhoyansk it is 100.

47 Maritime and continental warm winter(from -8 C to 0 C), cool summer (+16 C) and a large amount of precipitation (more than 800 mm), which falls evenly throughout the year. The temperate continental climate is characterized by fluctuations in air temperature from about -8 C in January to +18 C in July, the precipitation here is more than mm, which falls for the most part summer. The area of ​​continental climate is characterized by more low temperatures in winter period(up to -20 C) and less precipitation (about 600 mm). In the temperate sharply continental climate, winter will be even colder down to -40 C, and precipitation will be even less than mm.

48 Extremes Temperatures up to +55, and even up to +80 in deserts are observed in summer on the surface of bare soil in the Moscow region. Night temperature minima, on the contrary, are lower on the soil surface than in the air, since, first of all, the soil is cooled by effective radiation, and the air is already cooled from it. In winter in the Moscow region, nighttime temperatures on the surface (covered with snow at this time) can drop below 50, in summer (except July) to zero. On the snowy surface in the interior of Antarctica, even the average monthly temperature in June is about 70, and in some cases it can drop to 90.

49 Maps of average Air temperature January and July

50 Air temperature distribution (distribution zoning is the main factor of climatic zoning) Average annual Average summer (July) Average for January Average for latitudinal zones

51 Temperature regime of the territory of Russia It is characterized by great contrasts in winter. In Eastern Siberia, the winter anticyclone, which is an extremely stable baric formation, contributes to the formation of a cold pole in northeastern Russia with an average monthly air temperature in winter of 42 C. The average minimum temperature in winter is 55 C. winter changes from C in the southwest, reaching on the Black Sea coast positive values, to C in the central regions.

52 Average surface air temperature (С) in winter

53 Average surface air temperature (С) in summer The average air temperature varies from 4 5 C on the northern coasts to C in the southwest, where its average maximum is C and the absolute maximum is 45 C. The amplitude of extreme temperatures reaches 90 C. A feature of the air temperature regime in Russia is its large daily and annual amplitudes, especially in the sharply continental climate of the Asian territory. The annual amplitude varies from 8 10 C ETR to 63 C in Eastern Siberia in the region of the Verkhoyansk Range.

54 Effect of vegetation cover on soil surface temperature Vegetation cover reduces soil cooling at night. In this case, night radiation occurs mainly from the surface of the vegetation itself, which will be the most cooled. The soil under vegetation maintains a higher temperature. However, during the day, vegetation prevents the radiative heating of the soil. The daily temperature range under vegetation is reduced, and the average daily temperature is lowered. So, vegetation cover generally cools the soil. In the Leningrad region, the surface of the soil under field crops can be 15 degrees colder during the daytime than the soil under fallow. On average, per day it is colder than bare soil by 6, and even at a depth of 5-10 cm there is a difference of 3-4.

55 Effect of snow cover on soil temperature Snow cover protects the soil from heat loss in winter. The radiation comes from the surface of the snow cover itself, and the soil underneath remains warmer than the bare soil. At the same time, the daily temperature amplitude on the soil surface under snow sharply decreases. AT middle lane The European territory of Russia with a snow cover of 50 cm, the temperature of the soil surface under it is 6-7 higher than the temperature of the bare soil, and 10 higher than the temperature on the surface of the snow cover itself. Winter soil freezing under snow reaches depths of about 40 cm, and without snow it can spread to depths of more than 100 cm. Thus, vegetation cover in summer reduces the temperature on the soil surface, and snow cover in winter, on the contrary, increases it. The combined effect of vegetation cover in summer and snow cover in winter reduces the annual temperature amplitude on the soil surface; this is a decrease of the order of 10 compared to bare soil.

56 WEATHER HAZARDS AND THEIR CRITERIA 1. very strong wind(including flurry) not less than 25 m/s, (including gusts), on the coast of the seas and in mountainous areas not less than 35 m/s; 2. very heavy rain at least 50 mm for a period of not more than 12 hours 3. rainfall of at least 30 mm for a period of not more than 1 hour; 4. very heavy snow of at least 20 mm for a period of no more than 12 hours; 5. large hail - not less than 20mm; 6. strong blizzard - when average speed winds of at least 15 m/s and visibility of less than 500 m;

57 7. Strong dust storm with an average wind speed of at least 15 m/s and visibility of no more than 500 m; 8. Heavy fog visibility no more than 50m; 9. Severe ice-frost deposits of at least 20 mm for ice, at least 35 mm for complex deposits or wet snow, at least 50 mm for hoarfrost. 10. Strong heat - High Maximum temperature air at least 35 ºС for more than 5 days. 11. Severe frost - The minimum air temperature is not less than minus 35ºС for at least 5 days.

58 Dangerous phenomena associated with elevated temperatures Fire hazard Extreme heat

59 Low temperature hazards

60 Freeze. Freezing is a short-term decrease in air temperature or active surface (soil surface) to 0 C and below by general background positive average daily temperatures

61 Basic concepts of air temperature WHAT YOU NEED TO KNOW! Map of average annual temperature Differences in summer and winter temperatures Zonal distribution of temperature Influence of distribution of land and sea Altitude distribution of air temperature Daily and annual variation of soil and air temperature Hazardous weather phenomena due to temperature regime

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