What is the daily variation of temperature. Daily and annual changes in temperature over continents and seas

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 earth's surface, heat it up. 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. At the upper boundary of 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. This is why there is snow and ice on the tops of high mountains.

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 sun rays. 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 of 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 lowest temperatures occur 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 on weather stations Is the thermometer installed in a special booth?

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.

Measurements of air temperature and other meteorological elements are made in meteorological booths, where thermometers are placed at a height of two meters from the surface. Features of the daily and annual variations in air temperature are revealed by averaging the results over a long period of observations.

Daily variation of air temperature reflects the daily variation of the temperature of the earth's surface, but the moments of maximum and minimum temperature are somewhat delayed. The maximum air temperature over land is observed at 14-15 hours, over water bodies - about 16 hours, minimum over land - shortly after sunrise, over water bodies - 2 - 3 hours after sunrise. The difference between the daily maximum and minimum air temperature is called daily temperature range. It depends on a number of factors: the latitude of the place, the time of year, the nature of the underlying...
surface (land or body of water), cloudiness, relief, absolute height of the area, nature of vegetation, etc. In general, it is much greater over land (especially in summer) than over the Ocean. With altitude, daily temperature fluctuations fade: above land - at an altitude of 2 - 3 km, above the Ocean - lower.

Annual variation of air temperature-change average monthly temperatures air throughout the year. He also repeats annual course active surface temperature. Annual air temperature range- the difference between the average monthly temperatures of the warmest and coldest months. Its value depends on the same factors as the daily temperature amplitude and reveals similar patterns: it grows with increasing geographic latitude up to the polar circles (Fig. 29). This is due to the different influx of solar heat in summer and winter, mainly due to the changing angle of incidence of the sun's rays and due to the different duration of daily illumination throughout the year in temperate and high latitudes. The nature of the underlying surface is also very important: above land annual amplitude more - it can reach 60-65 °C, and above water it is usually less than 10-12 °C (Fig. 30).

Equatorial type. Annual temperatures The air temperature is high and even all year round, but still two small maximum temperatures are observed - - after the days of the equinoxes (April, October) and two small minimums - - after the days of the solstices (July, January). Over the continents, the annual temperature amplitude is 5-10 °C, on the coasts -3 °C, over the oceans - only about 1 °C (Fig. 31).

Tropical type. In the annual cycle, one maximum of air temperature is expressed - after the highest position of the Sun and one minimum - after the lowest position on the days of the solstices. Over the continents, the annual temperature range is mainly 10-15 °C due to very high summer temperatures; over the oceans it is about 5 °C.

Temperate latitude type. In the annual course of air temperature, the maximum and minimum, respectively, after the days of summer and winter solstice, and over the continents the temperature changes qualitatively throughout the year, passing through O °C (except for the western coasts of the continents). The annual temperature amplitude on the continents is 25-40 °C, and in the depths of Eurasia it reaches 60-65 °C due to very low winter temperatures; over the oceans and on the western coasts of the continents, where temperatures are positive all year round, the amplitude is small 10-15 °C.

IN temperate zone There are subtropical, temperate and subpolar subzones. All of the above referred to the temperate subzone itself. In general, within these three subzones, annual air temperature amplitudes increase with increasing latitude and with distance from the oceans.

Polar type characterized by harsh, long winters. In the annual course, there is also one maximum temperature of about 0 °C and lower - during the polar day and one significant minimum temperature - at the end of the polar night. The annual temperature range on land is 30 - 40 °C, over the oceans and on the coasts - about 20 °C.

Types of annual variations in air temperature are identified from average long-term data and reflect periodic seasonal fluctuations. Advection of air masses is associated with temperature deviations from average values ​​in individual years and seasons. The variability of average monthly air temperatures is more characteristic of temperate and nearby latitudes, especially in transition areas between marine and continental climates.

For the development of vegetation, derived temperature indicators are very important, such as, for example, the sum of active temperatures (the sum for a period with average daily temperatures above 10 °C). It largely determines the set of crops in a particular area

Changes in the temperature of the surface layer of air during the day and year are caused by periodic fluctuations in the temperature of the underlying surface and are most clearly expressed in its lower layers.

In a daily cycle, the curve has one maximum and one minimum. The minimum temperature value is observed before sunrise. Then it continuously increases, reaching highest values at 14...15 hours, after which it begins to decrease until sunrise.

Amplitude of temperature fluctuations - important characteristic weather and climate, depending on a number of conditions.

The amplitude of daily air temperature fluctuations depends on weather conditions. In clear weather, the amplitude is greater than in cloudy weather, since clouds linger during the day solar radiation, and at night they reduce heat loss from the earth’s surface by radiation.

The amplitude also depends on the time of year. IN winter months at low solar altitudes in mid-latitudes it drops to 2...3 °C.

Renders big influence relief on the daily variation of air temperature: on convex forms of relief (on the peaks and on the slopes of mountains and hills) the amplitude of daily fluctuations is smaller, and on concave forms of relief (depressions, valleys, basins) it is greater compared to flat terrain.

The amplitude assignment is influenced by physical properties soil:

The greater the diurnal variation on the soil surface itself, the greater the daily amplitude of air temperature above it.

Vegetation cover reduces the amplitude of daily fluctuations in air temperature among plants, since it delays solar radiation during the day and terrestrial radiation at night. Forests especially noticeably reduce daily amplitudes.

The annual variation of air temperature is characterized by the amplitude of annual air temperature fluctuations. It represents the difference between the average monthly air temperatures of the warmest and coldest months of the year.

Annual variation of air temperature in different geographical areas varies depending on latitude and continental™ location. According to the average long-term amplitude and time of onset extreme temperatures There are four types of annual variations in air temperature.

Equatorial type. IN equatorial zone In a year, two weak temperature maxima are observed - after the spring (03.21) and autumn (09.23) equinox, when the Sun is at its zenith, and two minimums - after the winter (12.22) and summer (06.22) solstice, when the Sun is at its lowest altitude.

Tropical type. In tropical latitudes, a simple annual variation in air temperature is observed with a maximum after the summer and a minimum after the winter solstice.

Temperate zone type. Minimum and maximum temperatures occur after the solstices.

Polar type. Due to the polar night, the minimum temperature in the annual cycle shifts to the time the Sun appears above. The maximum temperature in the Northern Hemisphere is observed in July.

The annual course of air temperature is also influenced by the altitude of a place above sea level. As altitude increases, the annual amplitude decreases.

TEMPERATURE AND HUMIDITY

Carnation- the most sensitive plant to temperature levels. The optimal temperature in the greenhouse largely determines the size of the harvest and the quality of flower products. As general characteristics crops, it can be argued that carnations do not like high temperatures, therefore, when growing in summer, it is necessary to especially carefully control the climate in the greenhouse. It is important to immediately increase the air humidity above 70% when temperatures rise during the hot months. For cloves, it is recommended to set the temperature in the greenhouse from 15°C at night to 25°C during the day. The temperature should be even, avoid sudden fluctuations. In the middle of winter, during short and especially cold days, the optimal temperature (if additional lighting is not used) is during the day and night. is the range from 8°C to 10°C. Temperature changes are not allowed. But the danger of the Botrytis fungus should be taken into account (do not allow the humidity to rise above 80% at such low temperatures). winter growing It is necessary to have a subsurface heating system. When using the ventilation system, prevent sudden increases in relative humidity.

For chrysanthemums. Constant and high relative air humidity of the order of 85% or more, especially during the flowering period, causes severe damage to plants by gray rot, powdery mildew, septoria, and can completely destroy the crop or significantly reduce its quality. This is especially true when using film greenhouses. Therefore, during the growth period they support relative humidity air at the level of 70-75%, and from the beginning of budding - 60-65%. If necessary, greenhouses are equipped with a forced ventilation system, for which they use various electric heaters. Particular care should be taken to ensure that dew does not form on the plants at night.

For tulips. For the formation of a flower bud, the optimal storage conditions for the bulbs will be a temperature within 17-20 degrees with a relative humidity of 70-75%. Violation temperature regime over a long period of time will lead to slow formation of flower buds and inferiority of tulips.

For narcissists. In a greenhouse for flowers, it is recommended to maintain optimal relative humidity. It should be between 70 and 85%

14. Evaporation from the surface of water, soil and plants

The amount of water evaporated from the soil surface and plants is called evapotranspiration. The total evaporation of agricultural fields is also determined by the thickness of the vegetation cover, biological features plants, the depth of the root layer, agrotechnical methods of cultivating plants, etc.

Evaporation is directly measured by evaporators or calculated using heat and water balance equations, as well as other theoretical and experimental formulas.

In practice, it is usually characterized by the thickness of the evaporated layer of water, expressed in millimeters.

To measure evaporation from the water surface, evaporation pools with an area of ​​20 and 100 m2, as well as evaporators with a surface area of ​​3000 cm2, are used. Evaporation in such pools and evaporators is determined by the change in water level taking into account precipitation.

Evaporation from the soil surface is measured by a soil evaporator with an evaporating surface area of ​​500 cm2 (Fig. 5.10). This evaporator consists of two metal cylinders. The outer one is installed in the soil to a depth of 53 cm. The inner cylinder contains a soil monolith with undisturbed soil structure and vegetation. The height of the monolith is 50 cm. The bottom of the inner cylinder has holes through which excess water from fallen rain flows into a drainage vessel. To determine evaporation, the inner cylinder with the soil monolith is removed from the outer cylinder every five days and weighed.

Soil evaporator GGI-500-50 1 - inner cylinder; 2 - outer cylinder; 3 - watershed. The coefficient 0.02 is used to convert weight units (g) to linear ones (mm). Evaporation measurements using a soil evaporator are carried out only in the warm season. Example 3 Determine evaporation based on observational data: On August 1, the monolith weighed 42,450 g. On August 6, 42,980 g. . From August 1 to August 6, 28.4 mm of precipitation fell

Calculation formula.

W from =A×F×d×(d w – d l /10³); (1)

W from = e×F×(P w – P l /10³); (2)

W from = F×(0.118 + (0.01995×a×(P w – P l /1.333)), where (3)

W from – the amount of moisture evaporating from the open water surface of the swimming pool;
A is an empirical coefficient that takes into account the number of people swimming;
F – area of ​​open water surface;
d = (25 + 19·V) - coefficient of moisture evaporation;
V – air speed above the water surface;
d w , d l – respectively, moisture content saturated air and air at a given temperature and humidity;
P w , P l – respectively, the water vapor pressure of saturated air in the pool at a given temperature and air humidity;
e - empirical coefficient equal to 0.5 - for closed pool surfaces, 5 - for fixed open pool surfaces, 15 - small private pools with limited time of use, 20 - for public pools with normal swimmer activity, 28 - for large leisure pools and entertainment, 35 – for water parks with significant wave formation;
a – coefficient of pool occupancy by people: 0.5 – for large public swimming pools, 0.4 – for hotel swimming pools, 0.3 – for small private swimming pools.
It should be noted that under the same conditions, comparative calculations carried out using the above formulas show a significant discrepancy in the amount of evaporated moisture. However, the results obtained from calculations using the last two formulas are more accurate. Moreover, calculations using the first formula, as practice shows, are most suitable for play pools. The second formula, in which the empirical coefficient makes it possible to take into account the highest evaporation rate in pools with active games, slides and significant wave formation, is the most universal and can be used for both water parks and small individual swimming pools.

The annual variation of air temperature is determined primarily by the annual variation 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. The amplitude of the annual variation of air temperature is influenced by:

Latitude of the place. The smallest amplitude is observed in the equatorial zone. With increasing latitude, the amplitude increases, reaching its greatest values ​​in polar latitudes

The height of the place above sea level. With increasing altitude above sea level, the amplitude decreases.

Weather. Fog, rain and mostly cloudy. The absence of clouds in winter leads to a decrease in the average temperature of the cold month, and in the summer - to an increase average temperature the warmest month.

Frost

Frost is a temperature drop to 0 °C or lower with positive average daily temperatures.

During frosts, the air temperature at a height of 2 m can sometimes remain positive, and in the lowest layer of air adjacent to the ground, drop to 0 ° C and below.

According to the conditions of frost formation, they are divided into:

radiation;

advective;

advective-radiative.

Radiation freezes arise as a result of radiative cooling of the soil and adjacent layers of the atmosphere. The occurrence of such frosts is favored by cloudless weather and light winds. Cloudiness reduces effective radiation and thus reduces the likelihood of frost. The wind also prevents frost from occurring, because it enhances turbulent mixing and, as a result, increases the flow of heat from the air to the soil. Radiation frosts are affected by the thermal properties of the soil. The lower its heat capacity and thermal conductivity coefficient, the stronger the frost.

Advective frost. They are formed as a result of advection of air having a temperature below 0 °C. When cold air invades, the soil cools upon contact with it, and therefore the temperature of the air and the soil differ little. Advective frosts cover large areas and are little dependent on local conditions.

Advective-radiation frosts. Associated with the invasion of cold, dry air, sometimes even having a positive temperature. At night, especially in clear or partly cloudy weather, additional cooling of this air occurs due to radiation, and frost occurs both on the surface and in the air.

Thermal balance of the active surface and atmosphere Thermal balance of the active surface

During the day, the active surface absorbs some part of the total radiation coming to it and the counter radiation of the atmosphere, but loses energy in the form of its own long-wave radiation. The heat received by the active surface is partially transferred into the soil or reservoir, and partially into the atmosphere. In addition, part of the resulting heat is spent on evaporating water from the active surface. At night there is no total radiation and the active surface usually loses heat in the form of effective radiation. At this time of day, heat from the depths of the soil or reservoir flows upward to the active surface, and heat from the atmosphere is transferred downward, that is, it also flows to the active surface. As a result of condensation of water vapor from the air on the active surface, the heat of condensation is released.

The total energy input and expenditure on the active surface is called its thermal balance.

Heat balance equation:

B = P + L + CW,

where B is the radiation balance;

P – heat flow between the active surface and the underlying layers;

L - turbulent heat flow in the surface layer of the atmosphere;

C·W – heat expended on the evaporation of water or released during condensation of water vapor on the active surface;

C – heat of evaporation;

W is the amount of water that evaporated from a unit surface during the time interval for which the heat balance was compiled.

Figure 2.3 – Diagram of the heat balance of the active surface

One of the main components of the thermal balance of the active surface is its radiation balance B, which is balanced by non-radiative heat flows L, P, CW.

Less important processes not taken into account in the heat balance:

Transfer of heat deep into the soil by precipitation that falls on it;

Heat consumption during decay processes, during radioactive decay of substances in the earth's crust;

The flow of heat from the bowels of the Earth;

Heat generation during industrial activities.

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 in individual 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 overall change in temperature at a fixed geographic point, depending on both individual changes in air conditions and advection, is called a local change.