Geography lesson "air temperature and daily temperature variation." Daily and annual variation of air temperature at the earth's surface Motivation for educational activities

The daily variation of air temperature is the change in air temperature during the day - in general it reflects the variation of the temperature of the earth's surface, but the moments of the onset of maximums and minimums are somewhat delayed, the maximum occurs at 14:00, 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 (greatest in tropical deserts– up to 400 C) and increases in places with bare soil. The daily amplitude of air temperature is one of the indicators of climate continentality. In deserts it is much greater than in areas with a maritime climate.

Annual variation of air temperature (change average monthly temperature throughout the year) is determined primarily 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 during the day is much higher than at higher latitudes, and even reaches the zenith at noon on the days of the equinox. i.e. it sends vertical rays and therefore gives greatest number heat. But this is not actually observed, since, in addition to latitude, the daily amplitude is also influenced by many other factors, 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 distant 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 amplitude increases from the coast to the interior of the continent. At the same time, the amplitude also depends on the time of year: in summer it is greater, in winter it is less; the difference is explained by the fact that the sun is higher in summer than in winter, and the duration summer day much more wintery. Further, the daily amplitude is influenced by cloudiness: it moderates the temperature difference between day and night, retaining the heat radiated from the earth at night, and at the same time moderating the effect 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 during the night all the heat they received during the day. In the Sahara, the daily air amplitude was observed to be 20-25° or more. There have been cases when, after high daytime temperatures, water even froze at night, and the temperature on the surface of the earth dropped 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 significantly smaller in areas covered with rich vegetation. Here, part of the heat received during the day is spent on 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 significantly rarefied, the heat inflow-outflow balance is sharply negative at night, and sharply positive during the day, so the daily amplitude here is sometimes greater than in deserts. For example, Przhevalsky during his trip to Central Asia observed daily fluctuations in air temperature in Tibet, even up to 30°, and on the high plateaus of the southern part North America(in Colorado and Arizona), daily fluctuations, as observations showed, reached 40°. Minor 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 generally in high latitudes, where the sun does not appear at all for days or months, at this time there are absolutely no daily temperature fluctuations. We can say that the daily variation of temperature merges at the poles with the annual one and winter represents night, and summer represents day. Of exceptional interest in this regard 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 tropics of the northern hemisphere, since it is here that the continents have the greatest extent, and the greatest deserts and plateaus are located here. The annual amplitude of temperature depends mainly on the latitude of the place, but, in contrast to the daily amplitude, the annual amplitude increases with distance from the equator to the pole. At the same time, the annual amplitude is influenced by all those factors that we have already dealt with when considering daily amplitudes. In the same way, fluctuations increase with distance from the sea inland, and the most significant amplitudes are observed, for example, in the Sahara and in Eastern Siberia, where the amplitudes are even more significant, because both factors play a role here: continental climate and high latitude, whereas in the Sahara the amplitude depends mainly on the continentality of the country. In addition, fluctuations also depend on the topographical nature of the area. To see how this last factor plays a significant role in the change in amplitude, it is enough to consider temperature fluctuations in the Jurassic and in the valleys. In summer, as is known, the temperature decreases quite quickly with height, so on lonely peaks, surrounded on all sides by cold air, the temperature is much lower than in the valleys, which are very hot in summer. In winter, on the contrary, cold and dense layers of air are located in the valleys, and the air temperature 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 their amplitude cannot be significant. The heating conditions for the central parts of the plateaus are already different. Heating strongly in the summer due to the rarefied air, they emit 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, but 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.

Daily allowance and annual course air temperature depends on inflow solar heat and the nature of the underlying surface. In accordance with the daily variation of intensity solar radiation the maximum air temperature during the day between the sea or ocean occurs at approximately 12 hours 30 minutes, and over land - about 14-15. The minimum air temperature occurs shortly before sunrise or at the moment of sunrise, i.e. during the period of greatest cooling of the earth surfaces. The difference between the maximum and minimum air temperature per day is called the daily temperature amplitude.

The magnitude of the daily amplitude of air temperature is far from constant and depends on the nature of the underlying surface, cloudiness, air humidity, time of year and, finally, on the latitude and altitude of the place.

The greatest daily amplitude of air temperature occurs in southern latitudes, over a sandy surface, in the warm season, in the absence of clouds and with low air humidity, i.e. in dry southern steppes or deserts. Under these conditions, the difference between the maximum and minimum temperatures per day can reach 25-30 and even 40°.

The presence of low clouds, fog, and precipitation greatly smooths out the daily temperature variation. The temperature amplitude in these cases is insignificant.

Daily amplitude of air temperature over the oceans and large seas at a great distance from the coast it is small and amounts to only 2-3°. In other words, as a rule, there are no significant changes in air temperature in the open sea (ocean) during the day. This relatively even daily cycle over the seas is explained by the thermal properties of water, which consist in its small and slow heating and cooling, which in the same way affects the temperature of the air adjacent to the water surface.

As for the annual variation of air temperature, it depends on the same reasons as the daily variation. On continents, the maximum usually occurs in July, the minimum in January, which coincides with the periods of the highest and lowest solstices. On the oceans and coasts, there is a delay in extreme temperatures: the maximum is observed in August, the minimum in February or early March.

IN equatorial zone two maximum temperatures are observed - after the spring and autumn equinox, when the height of the Sun is greatest, and two minimums after winter and summer solstice, at the lowest solar altitude of the year.

The difference between the maximum and minimum average monthly temperature during the year is called the annual temperature range. Its magnitude depends mainly on the nature of the underlying surface and the latitude of the place.

The smallest annual amplitude occurs over the oceans, especially between the tropics, where it is only 1-3°; V temperate latitudes it increases to 5-10°, and in polar regions it increases even more.

The greatest annual amplitude is observed over land, in the interior of continents in temperate and high latitudes, where it can reach 40-50°, and in some places even 65°. For example, in Verkhoyansk (Yakutia) the average temperature in July is plus 15°, and in January minus 50°. At low latitudes over land, the annual amplitude of air temperature is relatively small, which is explained by a more uniform influx of solar heat.

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 does clear air heat up?

HOW THE AIR HEATS. From natural history lessons you know that transparent air allows the sun's rays to reach the earth's surface and heat it. It is the air that is not heated by the rays, but is heated by the heated surface. Therefore, the further from the earth's surface, the colder it is. This is why when an airplane flies high above the ground for a long time, the air temperature is very low. On upper limit In the troposphere it drops to -56 °C.

It has been established that after every kilometer of altitude the air temperature decreases 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's why on the tops high mountains there is snow and ice.

HOW TO MEASURE AIR TEMPERATURE. Of course, everyone knows that air temperature is measured with a thermometer. However, it is worth remembering that an incorrectly installed thermometer, for example, in the sun, will not show 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 lattice. This allows air to freely enter the booth; together, the grilles protect the viya thermometer. direct sunlight. The booth is installed at a height of 2 m from the ground. Thermometer readings are recorded every 3 hours.

Rice. 126. Change in air temperature with altitude

Flying above the clouds

In 1862, two Englishmen flew on hot-air balloon. At an altitude of 3 km, passing the clouds, the researchers were shivering from the cold. When the clouds disappeared and the sun appeared, it became even colder. At a height of these 5 km, the water froze. It became difficult for people to breathe, there was a noise in their ears, and they were exhausted. Thus, the rarefied air was sprayed 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 in danger of death. Therefore, they descended to Earth as quickly as possible.

Rice. 127. Graph of daily air temperature

DAILY CHANGE OF TEMPERATURE. The sun's rays heat the Earth unevenly throughout the day (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 to three hours after noon (at 14-15 o'clock). This is because it takes time for heat to transfer from the earth's surface. After noon, 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, and the air temperature decreases accordingly. The most low temperatures happen before sunrise. True, on some days this daily temperature pattern may be disrupted.

Consequently, the reason for changes 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 temperature changes is given by graphs of the daily variation of air temperature (Fig. 127).

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

For example, if the highest air temperature during the day was +25 °C, and +9 °C, then the amplitude of fluctuations will be equal to 16 °C (25 - 9 = 16) (mat. 129). The daily amplitudes of temperature fluctuations are influenced by the nature of the earth's surface (it is called the underlying surface). 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 air temperature fluctuations

REMEMBER

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

The air temperature changes during the day due to changes in surface illumination (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 airplane flying at an altitude of 10 km.

2. Why is the 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 using 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.

PRACTICAL WORK 5 (Start. Continued, see pp. 133, 141.)

Topic: Solving problems on changes in air temperature with altitude.

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.

Reasons for changes in air temperature.

Air temperature changes daily 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.

An increase in air temperature begins along with an increase in soil temperature (15 minutes later) in the morning, after sunrise. At 13-14 hours the soil temperature, as we know, begins to drop. At 14-15 hours it equalizes with the air temperature; from this time, with a further drop in soil temperature, the air temperature begins to fall.

The diurnal variation of air temperature appears quite correctly only in conditions of stable clear weather.

But on some days the daily variation of air temperature can be very incorrect. This depends on changes in cloud cover as well as advection.

The daily amplitude of air temperature also varies by season, by latitude, and also depending on the nature of the soil and terrain. In winter it is less than in summer. With increasing latitude, the daily amplitude of air temperature decreases, as the midday height of the sun above the horizon decreases. At latitudes of 20-30° on land, the average annual daily temperature amplitude is about 12°, at latitude 60° about 6°, at latitude 70° only 3°. In the highest latitudes, where the sun does not rise or set for many days in a row, there is no regular daily temperature variation at all.

The temperature of the soil surface also changes throughout the year. IN tropical latitudes its annual amplitude, i.e., the difference between the 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° it is about 10°, at latitude 50° it averages about 25°.

Reasons for changes in air temperature

Air in direct contact with the earth's surface exchanges heat with it due to molecular thermal conductivity. But inside the atmosphere there is another, more efficient heat transfer - through turbulent thermal conductivity. The mixing of air during turbulence promotes very rapid transfer of heat from one layer of the atmosphere to another. Turbulent thermal conductivity also increases the transfer of heat from the earth's surface to the air or vice versa. If, for example, air is cooled from the earth's surface, then through turbulence more warm air from the overlying layers. This maintains a temperature difference between the air and the surface and therefore supports the process of heat transfer from air to surface. temperature changes associated with advection - the influx of new air masses from other parts globe, are called advective. If air flows into a given place with more high temperature, they speak of heat advection; if lower, they speak of cold advection.

The total change in temperature in the recorded geographical point, depending both on individual changes in the state of the air and on advection, is called a local (local) change.

Air temperature and daily temperature variation

Target: Form an idea of ​​the distribution of heat on the Earth's surface, the average daily temperature, the amplitude of temperature fluctuations (daily, annual).

Equipment: thermometer, textbook.

During the classes.

I .Organizing time. Rapport.

II . Examination homework

Test.

Which gas predominates in the atmosphere:

a) oxygen; b) hydrogen; c) carbon dioxide; d) nitrogen.

Which layer of the atmosphere contains most of the air?

At which latitudes is the troposphere thicker?

a) above the equator; b) in polar latitudes; c) in temperate latitudes.

Which layer of the atmosphere is located above the troposphere?

a) exosphere; b) stratosphere; c) mesosphere.

In which layer does the weather change occur?

a) in the stratosphere; b) in the troposphere; c) in the upper layers of the atmosphere.III . Learning new material. How is air heated?

How much of the solar energy do you think will heat the air in the troposphere?

Explain how temperature changes in the troposphere and with altitude. Why is the temperature dropping?

Reveal patterns :

The sun's rays pass through the atmosphere without heating it.

The sun's rays heat the Earth's surface

The air in the atmosphere is heated by the Earth's surface

Air temperature decreases with altitude. For every km the temperature drops by 6°C.

What is the reason for the unequal heating of the air during the day? Look at the picture on the slide and try to formulate a pattern.

Pattern : The higher the Sun is above the horizon, the greater the angle of incidence of the sun's rays, therefore, the better the surface of the Earth, and the air from it, warms up.

Daily variation of air temperature.

At what time of day is the air temperature highest and lowest? Explain.

How does temperature change throughout the year?

Think about why the warmest and coldest months are not June and December, when the sun's rays have the greatest and smallest angles of incidence on the earth's surface.

Air temperature is the degree of air heating, determined using a thermometer.

Air temperature is one of the most important characteristics of weather and climate.

Air temperature, as well as soil and water temperature in most countries is expressed in degrees international temperature scale, or scalesCelsius (WITH). Zero on this scale is the temperature at which ice melts, and +100 ˚C is the boiling point of water. However, in the USA and a number of other countries the scale is still used not only in everyday life, but also in meteorologyFahrenheit (F). On this scale, the interval between the melting point of ice and the boiling point of water is divided by 180˚, with the melting point of ice assigned a value of +32˚F. Zero Celsius corresponds to +32 ˚F, and +100 ˚С = +212 ˚F.

In addition, theoretical meteorology uses an absolute temperature scale (scaleKelvin ), K. Zero of this scale corresponds to complete cessation thermal movement molecules, that is, the lowest possible temperature. On the Celsius scale it will be −273 ˚С

To identify general patterns of temperature changes, an indicator of average temperatures is used: average daily, average monthly, average annual.

Determine the average annual temperature in Ust-Kamenogorsk

Examination:

Negative: -10°+(-7°)+(-2°)+(-2°)+(-6°)= -27°С

Positive: 6°+13°+17°+18°+16°+12°+5°=+87°С

Average dailyt: 87° - 27°= 60°: 12=+5°С

When determining a change in temperature, its highest and lowest values ​​are usually noted. The difference between the highest and the most low performance calledamplitude temperatures Write down the definition.

Determine the temperature amplitude using the table and diagrams on the slide .

Exercise : according to fig. 86, p.94 determine the amplitude of the air temperature using the readings of the third pair of thermometers.

Educational practical work.

Drawing up a graph of daily temperature variations (under the guidance of a teacher)

Isotherms - these are lines connecting points with the same average temperature air for a certain period of time.

Typically, isotherms are shown for the warmest and coldest months of the year, i.e. July and January.

IV . Consolidation of what has been learned.

Textbook page 94

V . Homework.

§24, questions

On Sunday, note the air temperature at 9:00, 12:00, 15:00, 18:00, 21:00. Enter the data into the table

9 hours

12 h

15 h

18 h

21 o'clock