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Annual temperature ranges. Let's get to know nature better

During the day the air temperature changes. The lowest temperature is observed before sunrise, the highest - at 14-15 hours.

To determine average daily temperature, You need to measure your temperature four times a day: at 1 a.m., at 7 a.m., at 1 p.m., at 7 p.m. The arithmetic mean of these measurements is the average daily temperature.

The air temperature changes not only during the day, but also throughout the year (Fig. 138).

Rice. 138. Head course of air temperature at latitude 62° N. latitude: 1 - Torshavn Denmark (sea mud), average annual temperature 6.3 ° C; 2- Yakutsk (continental type) - 10.7 °C

Average annual temperature is the arithmetic average of temperatures for all months of the year. It depends on geographic latitude, the nature of the underlying surface and the transfer of heat from low to high latitudes.

The Southern Hemisphere is generally colder than the Northern Hemisphere due to Antarctica being covered in ice and snow.

The warmest month of the year in the Northern Hemisphere is July, and the coldest month is January.

Lines on maps connecting points with the same air temperature are called isotherms(from the Greek isos - equal and therme - heat). About them difficult location can be judged from maps of January, July and annual isotherms.

The climate at the corresponding parallels in the Northern Hemisphere is warmer than at similar parallels in the Southern Hemisphere.

The highest annual temperatures on Earth are observed in the so-called thermal equator. It does not coincide with the geographic equator and is located at 10° N. w. This is explained by the fact that in the Northern Hemisphere large area is occupied by land, and in the Southern Hemisphere, on the contrary, by oceans, which waste heat on evaporation, and in addition, the influence of ice-covered Antarctica is felt. The average annual temperature at the parallel is 10° N. w. is 27 °C.

Isotherms do not coincide with parallels despite the fact that solar radiation is distributed zonally. They bend, moving from the continent to the ocean, and vice versa. Thus, in the Northern Hemisphere in January over the continent, isotherms deviate to the south, and in July - to the north. This is due to the unequal heating conditions of land and water. In winter, land cools, and in summer it warms up faster than water.

If we analyze isotherms in the Southern Hemisphere, then in temperate latitudes their course is very close to parallel, since there is little land there.

In January the most heat air temperature is observed at the equator - 27 ° C, in Australia, South America, central and southern parts Africa. The lowest January temperature was recorded in northeast Asia (Oymyakon, -71 °C) and at the North Pole -41 °C.

The “warmest July parallel” is the parallel of 20° N latitude. with a temperature of 28 ° C, and the coldest place in July is South Pole with an average monthly temperature of -48 °C.

The absolute maximum air temperature was recorded in North America(+58.1 °C). The absolute minimum air temperature (-89.2 °C) was recorded at the Vostok station in Antarctica.

Observations revealed the existence of daily and annual fluctuations in air temperature. The difference between the largest and lowest values air temperature during the day is called daily amplitude, and during the year - annual temperature range.

The daily temperature range depends on a number of factors:

latitude of the area - decreases when moving from low to high latitudes;
the nature of the underlying surface - it is higher on land than over the ocean: over oceans and seas the daily temperature amplitude is only 1-2 °C, and over steppes and deserts it reaches 15-20 °C, since water heats up and cools down more slowly than land ; in addition, it increases in areas with bare soil;
terrain - due to cold air descending into the valley from the slopes;
cloudiness - with its increase, the daily temperature amplitude decreases, since clouds do not allow the earth's surface to heat up strongly during the day and cool down at night.

The magnitude of the daily amplitude of air temperature is one of the indicators of the continental climate: in deserts its value is much greater than in areas with a marine climate.

Annual temperature range has patterns similar to the daily temperature amplitude. It depends mainly on the latitude of the area and the proximity of the ocean. Over the oceans, the annual temperature amplitude is most often no more than 5-10 °C, and over the interior regions of Eurasia - up to 50-60 °C. Near the equator, average monthly air temperatures differ little from each other throughout the year. At higher latitudes, the annual temperature range increases, and in the Moscow region it is 29 °C. At the same latitude, the annual temperature amplitude increases with distance from the ocean. In the equator zone above the ocean, the annual temperature amplitude is only G, and above the continents it is 5-10°.

The different heating conditions for water and land are explained by the fact that the heat capacity of water is twice that of land, and with the same amount of heat, land heats up twice faster than water. When cooling, the opposite happens. In addition, when heated, water evaporates, which consumes a significant amount of heat. It is also important that on land heat spreads almost only in top layer soil, and only a small part of it will be transmitted into depth. In the seas and oceans, significant thicknesses are heating up. This is facilitated by vertical mixing of water. As a result, the oceans accumulate much more heat than land, retain it longer, and expend it more evenly than land. The oceans are warming more slowly and cooling more slowly.

The annual temperature range in the Northern Hemisphere is 14 °C, and in the Southern Hemisphere - 7 °C. For the globe, the average annual air temperature at the earth's surface is 14 °C.

Heat zones

The uneven distribution of heat on Earth depending on the latitude of the place allows us to highlight the following thermal belts, the boundaries of which are isotherms (Fig. 139):

the tropical (hot) zone is located between the annual isotherms + 20 °C;
temperate zones of the Northern and Southern Hemispheres - between the annual isotherms of +20 °C and the isotherm of the warmest month +10 °C;
the polar (cold) belts of both hemispheres are located between the isotherms of the warmest month +10 °C and O °C;
Perpetual frost belts are limited by the 0 °C isotherm of the warmest month. This is the kingdom of eternal snow and ice.

Rice. 139. Heat zones Earth

The annual amplitude of surface temperatures is equal to the difference between the maximum and minimum average monthly temperatures. The annual amplitude of surface temperatures increases with increasing latitude, which is explained by increasing fluctuations in solar radiation. The annual temperature amplitude reaches its greatest values on the continents; On the oceans and seashores, annual temperature amplitudes are much smaller. The smallest annual temperature range is observed in equatorial latitudes, where it is 2-3°. The largest annual amplitude is in subarctic latitudes on the continents - more than 60°.

The annual variation of air temperature is determined primarily by the latitude of the place. The annual variation of air temperature is the change in average monthly temperature throughout the year. The annual amplitude of air temperature is the difference between the maximum and minimum average monthly temperatures. There are four types annual progress temperature; in each type there are two subtypes - marine and continental, characterized by different annual temperature amplitudes. In the equatorial type of annual temperature variation, two small maxima and two small minima are observed. Maximums occur after the equinoxes, when the Sun is at its zenith above the equator. In the marine subtype, the annual amplitude of air temperature is 1-2°, in the continental subtype it is 4-6°. The temperature is positive all year round.

In the tropical type of annual temperature variation there is one maximum after the day summer solstice and one minimum - after the day winter solstice in the Northern Hemisphere. In the marine subtype, the annual temperature amplitude is 5°, in the continental subtype it is 10-20°.

In the moderate type of annual temperature variation, one maximum is also observed after the summer solstice and one minimum after the winter solstice in the Northern Hemisphere; in winter temperatures are negative. Over the ocean, the annual temperature amplitude is 10-15°, over land it increases with distance from the ocean: on the coast - 10°, in the center of the continent - up to 60°.

In the polar type of annual temperature variation, there is one maximum after the summer solstice and one minimum after the winter solstice in the Northern Hemisphere; the temperature is negative most of the year. The annual temperature range at sea is 20-30°, on land - 60°.

The identified types of annual variation in air temperature reflect the zonal variation of temperature caused by the influx of solar radiation. On the annual variation of air temperature big influence renders movement air masses. In Europe, there is a return of cold weather associated with the invasion of Arctic air masses. In early autumn, heat returns associated with the invasion of tropical air. This phenomenon is called " Indian summer", sometimes the warming is so significant that fruit trees begin to bloom.

The geographic distribution of air temperature is shown using isotherms - lines connecting points on the map with the same temperatures. The distribution of air temperature is zonal; annual isotherms generally have a sublatitudinal extent and correspond to the annual distribution of the radiation balance. All parallels of the Northern Hemisphere are warmer than the southern ones, the differences are especially great at the polar latitudes. Antarctica is a planetary refrigerator and has a cooling effect on the Earth. The thermal equator - the strip of the highest annual temperatures- located in the Northern Hemisphere at latitude 10° N. In summer, the thermal equator shifts to 20° N, in winter it approaches the equator by 5° N. The shift of the thermal equator to the Northern Hemisphere is explained by the fact that in the Northern Hemisphere the land area located at low latitudes is larger compared to Southern Hemisphere; and it has higher temperatures throughout the year. The latitudinal distribution of annual isotherms is disturbed by warm and cold currents. In the temperate latitudes of the Northern Hemisphere, the western shores washed by warm currents, warmer than the eastern shores, along which cold currents pass. Consequently, isotherms along the western coasts bend toward the pole, and near the eastern coasts - toward the equator.

On the map of summer temperatures (July in the Northern Hemisphere and December in the Southern Hemisphere), the isotherms are located sublatitudinally, i.e. temperature regime determined by solar insolation. In summer, the continents are warmer, and isotherms over land bend toward the poles.

On the map winter temperatures(December in the Northern Hemisphere and July in the Southern Hemisphere), the isotherms deviate significantly from parallels. Over the oceans, isotherms move far to high latitudes, forming “heat tongues”; over land, isotherms deviate toward the equator. The 0 °C isotherm in North America runs at 40° N, off the coast of Europe - at 70° N. The deviation of isotherms to the north off the coast of Norway is due to the influence of the powerful warm North Atlantic Current and westerly winds.

The average annual temperature of the Northern Hemisphere is + 15.2 °C, and the Southern Hemisphere is + 13.2 °C. The minimum temperature in the Northern Hemisphere reached - 77 °C (Oymyakon) and - 68 °C (Verkhoyansk). In the Southern Hemisphere minimum temperatures much lower; at the Sovetskaya and Vostok stations, a temperature of - 89.2 "C was noted. The minimum temperature in clear weather in Antarctica can drop to - 93 °C. The highest temperatures are observed in deserts tropical zone, in Tripoli + 58 °C; in California, in Death Valley, the temperature was + 56.7°.

Anomaly maps give an idea of how strongly continents and oceans influence the distribution of temperatures. Isanomalies are lines connecting points with the same temperature anomalies. Anomalies are deviations of actual temperatures from average latitude temperatures. Anomalies can be positive or negative. Positive anomalies are observed in summer over warmed continents; over Asia, temperatures are 4° higher than mid-latitude ones. In winter, positive anomalies are located above warm currents; above the warm North Atlantic Current off the coast of Scandinavia, the temperature is 28 °C above normal. Negative anomalies are pronounced over cooled continents in winter and over cold currents in summer. For example, in Oymyakon in winter the temperature is 22 °C below normal.

The tropics and polar circles cannot be considered the actual boundaries of thermal (temperature) zones, since the distribution of temperatures is influenced by a number of other factors: the distribution of land and water, and currents. Isotherms are taken as the boundaries of thermal zones. The hot zone is located between the annual isotherms of 20 °C and outlines a strip of wild palm trees.

The boundaries of the temperate zone are drawn along the 10°C isotherm of the warmest month. In the Northern Hemisphere, the border coincides with the distribution of forest-tundra. The boundary of the cold belt follows the 0°C isotherm of the warmest month. Frost belts (regions) are located around the poles.

What does the precipitation map show?

Atmospheric precipitation is the name given to drops and crystals of water that fall onto the earth's surface from the atmosphere.

The droplets and crystals in the cloud are very small and are easily retained by rising air currents. For droplets to begin to grow, it is desirable to have droplets of different sizes or droplets and crystals in the cloud. If there are droplets of different sizes in the cloud, water vapor begins to move to larger droplets and their growth. Drops also grow when they collide with each other. Favorable condition For the formation of precipitation is the presence of ice crystals and water droplets in the cloud. In this case, evaporation of water droplets and sublimation of water vapor on the surface of the crystals is observed.

Precipitation over the earth's surface is distributed zonally. A visual representation of the distribution of precipitation is provided by the curved map. Isohyets are lines connecting points on the map with the same amount of precipitation. Maximum amount precipitation falls on the region low blood pressure with rising air currents: in the equatorial 1500-2000 mm per year and in temperate latitudes up to 1000 mm per year. At the equator, intramass precipitation is explained by thermal convection and unstable air stratification; in temperate latitudes, precipitation, mainly frontal, is formed on fronts during the movement of atmospheric vortices - cyclones. The minimum amount of precipitation is typical for areas with high blood pressure and downward air currents. In tropical latitudes the amount of precipitation is 100-200 mm per year (except for the eastern coasts), in polar latitudes over the ice sheets of Antarctica and Greenland - up to 100 mm per year. The absolute maximum precipitation occurs in the foothills of the Himalayas (Cherrapunji - 12,660 mm) and the Andes (Tutunendo, Colombia 11,770 mm). The minimum amount of precipitation is typical for the Atacama Desert - 1 mm.

In the annual precipitation regime, four types of annual precipitation are distinguished. The equatorial type of annual precipitation is characterized by almost uniform precipitation throughout the year with two small maximums after the days of the equinox; the total amount is 1500-2000 mm.

In the monsoon type of annual precipitation, there is one absolute summer maximum of precipitation; in winter there is little precipitation. The amount of precipitation in tropical latitudes is 1500 mm; in extratropical latitudes it decreases to 1000-700 mm.

The Mediterranean type of annual precipitation is characterized by a winter maximum associated with the activation of the polar front. In summer, with the dominance of a tropical air mass, the amount of precipitation decreases sharply. In this type, the total amount of precipitation decreases from 1000 mm on the western shores of the continents to 300 mm inland.

The temperate type has two subtypes - marine and continental. In the temperate marine subtype, precipitation is almost uniform throughout the year with a slight winter maximum; total precipitation is 1000-700 mm. The winter maximum precipitation is associated with increased cyclonic activity in the winter season. In the temperate continental subtype, a summer maximum of precipitation is observed, the amount of winter precipitation is slightly less. The summer maximum precipitation is explained by an increase in absolute air humidity with rising temperatures. In addition, convective precipitation is added, which is absent in winter. For the Moscow region, the average annual precipitation is 560-600 mm.

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The annual amplitude of surface temperatures is equal to the difference between the maximum and minimum average monthly temperatures. The annual amplitude of surface temperatures increases with increasing latitude, which is explained by increasing fluctuations in solar radiation. The annual temperature amplitude reaches its greatest values on the continents; On the oceans and seashores, annual temperature amplitudes are much smaller. The smallest annual temperature amplitude is observed in equatorial latitudes, where it is 2-3°. The largest annual amplitude is in subarctic latitudes on the continents - more than 60°.

The annual variation of air temperature is determined primarily by the latitude of the place. The annual variation of air temperature is the change in average monthly temperature throughout the year. The annual amplitude of air temperature is the difference between the maximum and minimum average monthly temperatures. There are four types of annual temperature variations; in each type there are two subtypes - marine and continental, characterized by different annual temperature amplitudes. In the equatorial type of annual temperature variation, two small maxima and two small minima are observed. Maximums occur after the equinoxes, when the Sun is at its zenith above the equator. In the marine subtype, the annual amplitude of air temperature is 1-2°, in the continental subtype it is 4-6°. The temperature is positive all year round.

In the tropical type of annual temperature variation, there is one maximum after the summer solstice and one minimum after the winter solstice in the Northern Hemisphere. In the marine subtype, the annual temperature amplitude is 5°, in the continental subtype it is 10-20°.

The identified types of annual variation in air temperature reflect the zonal variation of temperature caused by the influx of solar radiation. The annual course of air temperature is greatly influenced by the movement of air masses. In Europe, there is a return of cold weather associated with the invasion of Arctic air masses. In early autumn, heat returns associated with the invasion of tropical air. This phenomenon is called “Indian summer”; sometimes the warming is so significant that fruit trees begin to bloom.

The geographic distribution of air temperature is shown using isotherms - lines connecting points on the map with the same temperatures. The distribution of air temperature is zonal; annual isotherms generally have a sublatitudinal extent and correspond to the annual distribution of the radiation balance. All parallels of the Northern Hemisphere are warmer than the southern ones, the differences are especially great at the polar latitudes. Antarctica is a planetary refrigerator and has a cooling effect on the Earth. The thermal equator - the band of the highest annual temperatures - is located in the Northern Hemisphere at a latitude of 10° N. In summer, the thermal equator shifts to 20° N, in winter it approaches the equator by 5° N. The shift of the thermal equator to the Northern Hemisphere is explained by the fact that in the Northern Hemisphere the land area located at low latitudes is larger compared to the Southern Hemisphere; and it has higher temperatures throughout the year. The latitudinal distribution of annual isotherms is disturbed by warm and cold currents. In the temperate latitudes of the Northern Hemisphere, the western shores, washed by warm currents, are warmer than the eastern shores, along which cold currents pass. Consequently, isotherms along the western coasts bend toward the pole, and near the eastern coasts - toward the equator.

Lesson objectives:

Identify the causes of annual fluctuations in air temperature;
establish the relationship between the height of the Sun above the horizon and air temperature;
how to use a computer technical support information process.

Lesson Objectives:

Educational:

developing skills and abilities to identify the causes of changes in the annual variation of air temperatures in different parts of the earth;
plotting in Excel.

Educational:

developing students’ skills in drawing up and analyzing temperature graphs;
using Excel in practice.

Educational:

nurturing interest in native land, ability to work in a team.

Lesson type: Systematization of ZUN and use of a computer.

Teaching Method: Conversation, oral questioning, practical work.

Equipment: Physical map of Russia, atlases, personal computers(PC).

During the classes

I. Organizational moment.

II. Main part.

Teacher: Guys, you know that the higher the Sun is above the horizon, the greater the angle of inclination of the rays, so the surface of the Earth, and from it the air of the atmosphere, heats up more. Let's look at the picture, analyze it and draw a conclusion.

Student work:

Work in a notebook.

Record in the form of a diagram. Slide 3

Recording in text.

Heating of the earth's surface and air temperature.

The earth's surface is heated by the Sun, and from it the air is heated.
The earth's surface heats up in different ways:
- depending on the different heights of the Sun above the horizon;
- depending on the underlying surface.
air above earth's surface has different temperatures.

Teacher: Guys, we often say that it is hot in the summer, especially in July, and cold in January. But in meteorology, in order to establish which month was cold and which was warmer, they calculate from average monthly temperatures. To do this, you need to add up all the average daily temperatures and divide by the number of days of the month.

For example, the sum of average daily temperatures for January was -200°C.

200: 30 days ≈ -6.6°C.

By monitoring air temperatures throughout the year, meteorologists have found that the highest air temperatures are observed in July and the lowest in January. And we also found out that the Sun occupies its highest position in June -61° 50’, and its lowest in December 14° 50’. These months have the longest and shortest day lengths - 17 hours 37 minutes and 6 hours 57 minutes. So who is right?

Student answers: The thing is that in July the already heated surface continues to receive, although less than in June, but still a sufficient amount of heat. Therefore, the air continues to heat up. And in January, although the arrival of solar heat is already increasing somewhat, the surface of the Earth is still very cold and the air continues to cool from it.

Determination of annual air amplitude.

If you find the difference between average temperature the warmest and coldest months of the year, then we will determine the annual amplitude of air temperature fluctuations.

For example, the average temperature in July is +32°C, and in January -17°C.

32 + (-17) = 15° C. This will be the annual amplitude.

Determination of average annual air temperature.

To find the average temperature of the year, you need to add everything up average monthly temperatures and divide by 12 months.

For example:

Student work: 23:12 ≈ +2° C- average annual temperature air.

Teacher: You can also determine the long-term temperature of the same month.

Determination of long-term air temperature.

For example: average monthly temperature in July:

1996 - 22°C
1997 - 23°C
1998 - 25°C

Children's work: 22+23+25 = 70:3 ≈ 24° C

Teacher: Now guys, find on physical map Russian city of Sochi and the city of Krasnoyarsk. Determine their geographic coordinates.

Students use atlases to determine the coordinates of cities; one of the students shows the cities on the map at the board.

Practical work.

Today on practical work, which you perform on a computer, you will have to answer the question: Will the air temperature graphs coincide for different cities?

Each of you has a piece of paper on your desk that shows the algorithm for doing the work. The PC stores a file with a ready-to-fill table containing free cells for entering formulas used in calculating the amplitude and average temperature.

Algorithm for performing practical work:

Open the My Documents folder, find the Practical file. work 6th grade
Enter the air temperature values in Sochi and Krasnoyarsk into the table.
Using the Chart Wizard, build a graph for the values of the range A4: M6 (give the name of the graph and axes yourself).
Enlarge the plotted graph.
Compare (orally) the results obtained.
Save the work under the name PR1 geo (last name).

month	Jan.	Feb.	March	Apr.	May	June	July	Aug.	Sep.	Oct.	Nov.	Dec.
Sochi	1	5	8	11	16	22	26	24	18	11	8	2
Krasnoyarsk	-36	-30	-20	-10	+7	10	16	14	+5	-10	-24	-32

III. The final part of the lesson.

Do your temperature graphs coincide for Sochi and Krasnoyarsk? Why?
In which city are more celebrated? low temperatures air? Why?

Conclusion: The greater the angle of incidence of the sun's rays and the closer the city is located to the equator, the higher the air temperature (Sochi). The city of Krasnoyarsk is located further from the equator. Therefore, the angle of incidence of the sun's rays is smaller here and the air temperature readings will be lower.

Homework: paragraph 37. Construct a graph of air temperatures based on your weather observations for the month of January.

Literature:

Geography 6th grade. T.P. Gerasimova N.P. Neklyukova. 2004.
Geography lessons 6th grade. O.V. Rylova. 2002.
Lesson developments 6th grade. ON THE. Nikitina. 2004.
Lesson developments 6th grade. T.P. Gerasimova N.P. Neklyukova. 2004.

Amplitudes, daily and annual. Daily amplitude, i.e. The difference between the average temperature of the warmest (shortly after noon) and coldest (around sunrise) times of the day also serves as a characteristic of climate. Depending on the position of the Earth relative to the Sun, one should expect the greatest daily amplitude near the equator, because there during the whole year a lot of heat is received from the sun during the day, and the night is long and at this time a lot of heat is lost through radiation. There should be no daily temperature amplitude at the poles.

Due to geographical conditions, now existing on globe, neither the equator has the greatest diurnal amplitude, nor (probably) north pole greatest annual. In both cases, the largest amplitude is found in continental climates, namely the largest annual amplitude is between 60-70° in Eastern Siberia, and the largest daily amplitude is probably in the highlands of Asia, between 30-40°. At the equator, the relatively small daily amplitude on the African and South American continents depends on climate humidity and large quantity forests, the rest of the strip is close to the sea.

The daily temperature amplitude depends to a very large extent on topographic conditions, especially in clear and calm weather, i.e. during the day it will be warmer at the bottom of the valleys and colder at night than on the hills. The annual amplitude depends much more than the daily amplitude on geographical conditions and, to a lesser extent, on topographic ones. In other words, it depends more on large features, such as proximity or distance from the sea, the topography of the country, etc., than on smaller local topographic conditions. This difference between the daily and annual amplitude is easily explained: the first occurs at such a short time that very large temperature differences are possible in close places, which do not have time to smooth out.

Temperature changes throughout the year are much slower, and therefore very sharp differences in nearby places have time to smooth out. To give a clear idea of how different the speed of action is in both cases, it is enough to mention that even in Verkhoyansk, where observations gave the largest annual amplitude (more than 67 ° C.), the largest temperature difference between two neighboring months is still -still less than 24° (October -15.8° C., November -38.8° C.), therefore, per day less than 0.8° C., meanwhile in Madrid the average temperature difference is between 7 and 8 o’clock in the morning in July 2.4° C., in Nukus on the Amu Darya, between 7 and 8 o'clock in the morning in October 3.9° C. The rate of change is 3.9:0.8/24=117:1. It is also necessary to take into account that Verkhoyansk represents approximately the extreme type of large annual amplitude; if where in eastern Siberia and there is a large one, perhaps by 1° or 2°, meanwhile Nukus is far from representing the extreme type of large daily amplitude, even in the neighboring sandy steppes it is much larger, and even more, of course, in the Sahara and on the high plateaus, especially in Tibet .

There is no doubt that, in addition to air temperature, heating is of great importance sun rays. Unfortunately, the methods for studying these phenomena are still very inaccurate and there are very few observations.

Soil and water surface temperature. Great importance have the temperatures of soil surfaces (or rocks) and water. Air, due to its low heat capacity, perceives the temperature of the underlying solid or liquid medium. But, however, it would be unfair to think that the temperature of the lower layer of air is always equal to the temperatures of the upper layer of water, soil or plants. Over large bodies of water, especially oceans, these temperatures are quite close to each other and, on average, the air is somewhat colder than the surface of the water.

This closeness depends on the fact that the surface temperature of the water varies only slowly in space and time. Therefore, the air temperature, so to speak, keeps pace with these changes. Things are different on land. It can be taken as a rule that on every clear day around noon, if the sun's altitude is more than 30°, the temperature of the land surface is significantly higher than the air temperature, and when higher altitude sun and soil not covered by plants, the latter is 20° or more warmer than the air. This depends on two reasons: 1) the temperature of the soil surface quickly increases under the sun's rays, 2) the lower layer of air, heated by the soil, becomes lighter and rises, and colder air from above descends in its place.

Conversely, the air can be warmer than the soil surface for a long time in cloudy weather and warm winds, for example in our autumn, and in Western Europe and in winter: the heat capacity of the air is so small that these warm currents have very little effect on the soil surface. In winter, when there is snow on the ground, it, like a bad conductor, protects it from cooling, and the surface of the snow cools very much, and from it the lower layer of air. From this we can conclude that in the annual average, the temperature of the soil surface is much higher than the air temperature: 1) the climate in deserts (most likely in the southern Sahara) under the influence of strong heating of the dry surface by the sun's rays; 2) in a climate with very cold and long winters and deep snow (most likely in northeastern Siberia), under the influence of soil protection from cooling by snow cover.

Humidity, precipitation, evaporation. Air humidity absolute and relative (see). Evaporation and cloudiness (see). Precipitation (see Rain). These phenomena collectively are sometimes called hydrometeors. Just as climates can be distinguished as more or less cold, so, obviously, they can be classified according to more or less humidity or cloudiness, and according to more or less precipitation. In climate, the relationship of absolute and relative humidity to temperature and its changes deserves special attention. In a daily period, with clear weather and high midday altitude, the temperature increases very quickly from early morning to midday.

Evaporation, especially among continents, does not follow a rapid rise in temperature, and in very dry climates there is nothing to evaporate, so absolute humidity in the warm hours of the day differs little from the morning and therefore relative humidity decreases from early morning to mid-day and increases again as the temperature drops in the evening and at night until early morning.

We can take it as a rule that the daily amplitude of relative humidity increases parallel to the daily amplitude of temperature, and by the hours of the day their movement is opposite: the first decreases when the second increases, and vice versa. Both amplitudes are especially large in warm and dry climates, at high midday sun heights, and are barely noticeable at very low midday sun heights and cloudy weather, for example in our winter.

Another thing - annual period. Temperature changes occur so slowly that absolute humidity to some extent keeps pace with them, and where there are no local sources of evaporation from the seas or other waters, vegetation in full development, moist soil, water vapor is distributed by winds and diffusion. In general, more or less in the annual period, absolute humidity increases and decreases as the temperature rises or falls, and relative humidity is more or less less in summer than in winter.

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