Earth climates. Arid climate of low latitudes. Semi-arid climate of temperate latitudes

Climate- this is a long-term weather regime typical for a particular area. It manifests itself in the regular change of all types of weather observed in this area.

The climate has an impact on living and inanimate nature. Water bodies, soil, vegetation, animals are closely dependent on the climate. Certain sectors of the economy, primarily agriculture, are also highly dependent on the climate.

The climate is formed as a result of the interaction of many factors: quantity solar radiation coming to the earth's surface; circulation of the atmosphere; the nature of the underlying surface. At the same time, climatic factors themselves depend on the geographical conditions of a given area, primarily on geographic latitude.

The geographic latitude of the area determines the angle of incidence of the sun's rays, the receipt of a certain amount of heat. However, the receipt of heat from the Sun also depends on proximity to the ocean. In places far from the oceans, there is little precipitation, and the mode of precipitation is uneven (more in the warm period than in the cold), the cloud cover is low, the winter is cold, the summer is warm, the annual temperature range is large. This climate is called continental because it is typical for places located in the interior of the continents. Above the water surface, a maritime climate is formed, which is characterized by: a smooth course of air temperature, with small daily and annual temperature ranges, large cloud cover, uniform and sufficiently large amount of atmospheric precipitation.

The climate is greatly influenced by sea ​​currents. Warm currents warm the atmosphere in the areas where they flow. For example, the warm North Atlantic Current creates favorable conditions for the growth of forests in the southern part of the Scandinavian Peninsula, while most of Greenland, which lies at approximately the same latitudes as the Scandinavian Peninsula, but is outside the zone of influence of the warm current, all year round covered with a thick layer of ice.

An important role in the formation of the climate belongs relief. You already know that as the terrain rises, the air temperature drops by 5-6 ° С for every kilometer. Therefore, on the high mountain slopes of the Pamirs, the average annual temperature is 1 ° C, although it is located slightly north of the tropic.

The location of mountain ranges has a great influence on the climate. For example, the Caucasus Mountains hold back moist sea winds, and significantly more precipitation falls on their windward slopes facing the Black Sea than on the leeward ones. At the same time, the mountains serve as an obstacle to cold northern winds.

The climate is also dependent on prevailing winds. On the territory of the East European Plain, westerly winds coming from the Atlantic Ocean prevail throughout almost the entire year, therefore winters in this area are relatively mild.

Districts Of the Far East are under the influence of monsoons. In winter, winds constantly blow from the depths of the mainland. They are cold and very dry, so there is little rainfall. In summer, on the contrary, winds bring a lot of moisture from the Pacific Ocean. In autumn, when the wind dies down from the ocean, the weather is usually sunny and calm. This is the best time of the year in the area.

Climatic characteristics represent statistical conclusions from long-term series of weather observations (in temperate latitudes, 25-50-year series are used; in the tropics, their duration may be shorter), primarily over the following main meteorological elements: atmospheric pressure, wind speed and direction, temperature and humidity, cloudiness and atmospheric precipitation... The duration of solar radiation, visibility range, temperature of the upper layers of soil and water bodies, evaporation of water from the earth's surface into the atmosphere, the height and state of the snow cover, different atmospheric phenomena and terrestrial hydrometeors (dew, ice, fog, thunderstorms, blizzards, etc.). In the XX century. the number of climatic indicators included the characteristics of the elements heat balance the earth's surface, such as total solar radiation, radiation balance, heat transfer values ​​between the earth's surface and the atmosphere, heat consumption for evaporation. Complex indicators are also used, i.e. functions of several elements: various coefficients, factors, indices (for example, continentality, aridity, moisture), etc.

Climatic zones

Long-term average values ​​of meteorological elements (annual, seasonal, monthly, daily, etc.), their sums, frequency of occurrence, etc. are called climatic norms: the corresponding values ​​for individual days, months, years, etc. are considered as deviations from these norms.

Climate maps are called climatic(temperature distribution map, pressure distribution map, etc.).

Depending on temperature conditions, prevailing air masses and winds, they emit climatic zones.

The main climatic zones are:

• equatorial;
• two tropical;
• two moderate;
• arctic and antarctic.

Transitional climatic zones are located between the main belts: subequatorial, subtropical, subarctic, subantarctic. In the transition zones, air masses change with the seasons. They come here from neighboring zones, so the climate of the subequatorial zone in summer is similar to the climate of the equatorial zone, and in winter - to the tropical climate; the climate of the subtropical zones in summer is similar to the climate of the tropical, and in winter - with the climate of the temperate zones. This is due to the seasonal movement of the belts of atmospheric pressure over the earth after the Sun: in the summer - to the north, in the winter - to the south.

Climatic zones are subdivided into climatic regions. For example, in the tropical zone of Africa, areas of tropical dry and tropical humid climates are distinguished, and in Eurasia, the subtropical belt is subdivided into areas of the Mediterranean, continental and monsoon climates. In mountainous areas, altitudinal zonality due to the fact that the air temperature decreases with height.

The variety of climates on Earth

Climate classification provides an ordered system for characterizing climate types, their regionalization and mapping. Let us give examples of the types of climate prevailing over vast territories (Table 1).

Arctic and Antarctic climatic zones

Antarctic and arctic climate dominates in Greenland and Antarctica, where average monthly temperatures are below 0 ° C. In the dark winter season, these regions do not receive any solar radiation at all, although there are twilight and auroras. Even in summer, the sun's rays fall on the earth's surface at a slight angle, which reduces the heating efficiency. Most of incoming solar radiation is reflected by ice. Both summer and winter, the elevated regions of the Antarctic Ice Sheet are characterized by low temperatures. The climate of the interior regions of Antarctica is much colder than the climate of the Arctic, since the southern continent is large and high, and the Arctic Ocean softens the climate, despite the widespread distribution of pack ice. In summer, during short warmings, drifting ice sometimes melts. Precipitation on ice sheets falls in the form of snow or small particles of ice fog. The interior regions receive only 50-125 mm of precipitation annually, but more than 500 mm can fall on the coast. Sometimes cyclones bring clouds and snow to these areas. Snowfalls are often accompanied by strong winds that carry significant amounts of snow, blowing it off the slope. Strong katabatic winds with blizzards blow from the cold ice sheet, carrying snow to the coast.

Table 1. Climates of the Earth

Climate type	Climatic belt	Average temperature, ° С		Mode and amount of atmospheric precipitation, mm	Circulation of the atmosphere	Territory
Equatorial	Equatorial			During a year. 2000	In the area of ​​low atmospheric pressure, warm and humid equatorial air masses are formed	Equatorial regions of Africa, South America and Oceania
Tropical monsoon	Subequa-torial			Mostly during the summer monsoon, 2000		South and Southeast Asia, West and Central Africa, Northern Australia
Tropical dry	Tropical			Throughout the year, 200		North Africa, Central Australia
Mediterranean	Subtropical			Mainly in winter, 500	In summer - anticyclones at high atmospheric pressure; in winter - cyclonic activity	Mediterranean, Southern coast of Crimea, South Africa, Southwestern Australia, Western California
Subtropical dry	Subtropical			During a year. 120	Dry continental air masses	Inner parts of the continents
Moderate marine	Moderate			During a year. 1000	Westerly winds	Western Eurasia and North America
Moderate continental	Moderate			During a year. 400	Westerly winds	Inner parts of the continents
Moderate monsoon	Moderate			Mainly during the summer monsoon, 560		Eastern edge of Eurasia
Subarctic	Subarctic			Throughout the year, 200	Cyclones prevail	Northern outskirts of Eurasia and North America
Arctic (antarctic)	Arctic (Antarctic)			Throughout the year, 100	Anticyclones prevail	Arctic Ocean and mainland Australia

Subarctic continental climate formed in the north of the continents (see. climate map atlas). In winter, arctic air prevails here, which forms in areas of high pressure. Arctic air spreads from the Arctic to the eastern regions of Canada.

Continental subrctic climate in Asia is characterized by the largest the globe annual amplitude air temperature (60-65 ° C). The continentality of the climate here reaches its maximum value.

The average temperature in January varies across the territory from -28 to -50 ° C, and in lowlands and basins, due to stagnation of air, its temperature is even lower. In Oymyakon (Yakutia), a record negative air temperature (-71 ° С) for the Northern Hemisphere was recorded. The air is very dry.

Summer in subarctic belt although short, it is quite warm. The average monthly temperature in July ranges from 12 to 18 ° C (daily maximum - 20-25 ° C). Over the summer, more than half of the annual precipitation falls, amounting to 200-300 mm on the flat territory, and on the windward slopes of the hills - up to 500 mm per year.

The climate of the subarctic belt of North America is less continental in comparison with the corresponding climate in Asia. There are less cold winters and colder summers.

Moderate climatic zone

Moderate climate of the western coasts of the continents has pronounced features of the maritime climate and is characterized by the predominance of sea air masses throughout the year. It is observed on the Atlantic coast of Europe and the Pacific coast of North America. The Cordillera are the natural border separating the maritime coastline from the inland areas. The European coast, except for Scandinavia, is open to free access to maritime temperate air.

The constant transport of sea air is accompanied by large clouds and causes protracted springs, in contrast to the interior of the continental regions of Eurasia.

Winter in temperate the western coasts are warm. The warming influence of the oceans is enhanced by warm sea currents washing the western shores of the continents. The average temperature in January is positive and varies across the territory from north to south from 0 to 6 ° С. During incursions of the Arctic air, it can decrease (on the Scandinavian coast to -25 ° С, and on the French coast - to -17 ° С). When tropical air spreads to the north, the temperature rises sharply (for example, it often reaches 10 ° C). In winter, on the western coast of Scandinavia, there are large positive temperature deviations from the average latitudinal temperature (by 20 ° C). The temperature anomaly on the Pacific coast of North America is less and does not exceed 12 ° C.

Summers are rarely hot. The average temperature in July is 15-16 ° C.

Even during the day, the air temperature rarely exceeds 30 ° C. Due to frequent cyclones, cloudy and rainy weather is typical for all seasons. There are especially many cloudy days on the west coast of North America, where cyclones are forced to slow down in front of the Cordillera mountain systems. In this regard, the weather regime in the south of Alaska, where there are no seasons in our understanding, is characterized by great uniformity. Eternal autumn reigns there, and only plants remind of the onset of winter or summer. Annual precipitation ranges from 600 to 1000 mm, and on the slopes of mountain ranges - from 2000 to 6000 mm.

In conditions of sufficient moisture on the coasts, broadleaf forests, and in conditions of excess - conifers. The lack of summer heat reduces the upper border of the forest in the mountains to 500-700 m above sea level.

Moderate climate of the eastern coasts of the continents has monsoon features and is accompanied by a seasonal change of winds: in winter, northwestern flows prevail, in summer - southeastern ones. It is well defined on the east coast of Eurasia.

In winter, with a north-westerly wind, cold continental temperate air spreads to the coast of the mainland, which is the reason for the low average temperature of the winter months (from -20 to -25 ° C). Clear, dry, windy weather prevails. There is little precipitation in the southern regions of the coast. The north of the Amur region, Sakhalin and Kamchatka are often affected by cyclones moving over the Pacific Ocean. Therefore, in winter there is a thick snow cover, especially in Kamchatka, where its maximum height reaches 2 m.

In summer, with a southeasterly wind on the coast of Eurasia, maritime temperate air spreads. Summers are warm, with an average July temperature of 14 to 18 ° C. Precipitation is frequent due to cyclonic activity. Their annual number is 600-1000 mm, with most of them falling in summer. Fogs are frequent at this time of the year.

Unlike Eurasia, the east coast of North America is characterized by marine features climate, which are expressed in the predominance of winter precipitation and sea ​​type annual course air temperature: the minimum occurs in February, and the maximum in August, when the ocean is warmest.

The Canadian anticyclone, in contrast to the Asian, is unstable. It forms off the coast and is often interrupted by cyclones. Winters are mild, snowy, wet and windy here. In snowy winters, the height of snowdrifts reaches 2.5 m. south wind ice often occurs. Therefore, some streets in some cities in eastern Canada have iron railings for pedestrians. Summers are cool and rainy. Annual precipitation is 1000 mm.

Moderate continental climate most clearly expressed on the Eurasian continent, especially in the regions of Siberia, Transbaikalia, northern Mongolia, as well as in the Great Plains in North America.

A feature of moderate continental climate is a large annual amplitude of air temperature, which can reach 50-60 ° C. In the winter months, with a negative radiation balance, the earth's surface is cooled. The cooling effect of the land surface on the surface layers of air is especially great in Asia, where a powerful Asian anticyclone forms in winter and cloudy, calm weather prevails. The temperate continental air forming in the area of ​​the anticyclone has a low temperature (-0 ° ...- 40 ° C). In valleys and basins, due to radiation cooling, the air temperature can drop to -60 ° C.

In the middle of winter, the continental air in the lower layers becomes even colder than the arctic. This very cold air of the Asian anticyclone spreads to Western Siberia, Kazakhstan, southeastern regions of Europe.

The winter Canadian anticyclone is less stable than the Asian anticyclone due to the smaller size of the North American continent. Winters are less severe here, and their severity does not increase towards the center of the mainland, as in Asia, but, on the contrary, decreases somewhat due to the frequent passage of cyclones. Continental temperate air in North America has a higher temperature than continental temperate air in Asia.

The formation of a continental temperate climate is significantly influenced by the geographical features of the continental territory. In North America, the Cordillera mountain ranges are the natural boundary separating the maritime coast from the inland continental regions. In Eurasia, a temperate continental climate is formed over a vast land area, approximately from 20 to 120 ° E. e. Unlike North America, Europe is open for free penetration of sea air from the Atlantic deep into the interior regions. This is facilitated not only by the western transport of air masses, which prevails in the temperate latitudes, but also by the flat relief, strong indented coasts and deep penetration into the land of the Baltic and North Seas. Therefore, a temperate climate of a lesser degree of continentality is formed over Europe as compared to Asia.

In winter, the Atlantic sea air, moving over the cold land surface of the temperate latitudes of Europe, retains its physical properties for a long time, and its influence extends to the whole of Europe. In winter, with the weakening of the Atlantic influence, the air temperature decreases from west to east. In Berlin, it is 0 ° C in January, -3 ° C in Warsaw, and -11 ° C in Moscow. In this case, the isotherms over Europe have a meridional direction.

A broad front facing Eurasia and North America Arctic basin promotes deep penetration of cold air masses to the continents throughout the year. Intense meridional air mass transfer is especially characteristic of North America, where arctic and tropical air often replace each other.

Tropical air entering the plains of North America from southern cyclones, also slowly transforms due to the high speed of its movement, high moisture content and continuous low clouds.

In winter, the consequence of the intense meridional circulation of air masses is the so-called "jumps" in temperatures, their large day-to-day amplitude, especially in areas where cyclones are frequent: in the north of Europe and Western Siberia, the Great Plains of North America.

In the cold period, it falls in the form of snow, a snow cover forms, which protects the soil from deep freezing and creates a supply of moisture in the spring. The depth of the snow cover depends on the duration of its occurrence and the amount of precipitation. In Europe, a stable snow cover on the plains forms to the east of Warsaw, its maximum height reaches 90 cm in the northeastern regions of Europe and Western Siberia. In the center of the Russian Plain, the height of the snow cover is 30-35 cm, and in Transbaikalia - less than 20 cm. On the plains of Mongolia, in the center of the anticyclonic region, the snow cover is formed only in some years. The absence of snow, along with the low winter air temperature, leads to the presence of permafrost, which is no longer observed anywhere on the globe below these latitudes.

In North America, on the Great Plains, snow cover is negligible. To the east of the plains, tropical air increasingly begins to take part in frontal processes, it aggravates frontal processes, which causes heavy snowfalls. In the Montreal area, the snow cover lasts up to four months, and its height reaches 90 cm.

Summers in the continental regions of Eurasia are warm. The average July temperature is 18-22 ° C. In the arid regions of southeastern Europe and Central Asia average temperature air in July reaches 24-28 ° С.

In North America, continental air is somewhat colder in summer than in Asia and Europe. This is due to the lesser extent of the continent in latitude, the large indentedness of its northern part by bays and fjords, the abundance of large lakes, and the more intense development of cyclonic activity in comparison with the inner regions of Eurasia.

In the temperate zone, the annual precipitation on the flat territory of the continents varies from 300 to 800 mm, more than 2000 mm falls on the windward slopes of the Alps. Most of the precipitation falls in summer, which is primarily associated with an increase in the moisture content of the air. In Eurasia, there is a decrease in precipitation across the territory from west to east. In addition, the amount of precipitation also decreases from north to south due to a decrease in the frequency of cyclones and an increase in air dryness in this direction. In North America, a decrease in precipitation across the territory is noted, on the contrary, in the direction to the west. Why do you think?

Most of the land in the continental temperate zone is occupied by mountain systems. These are the Alps, Carpathians, Altai, Sayan, Cordillera, Rocky Mountains, etc. In mountainous regions, climatic conditions differ significantly from the climate of the plains. In summer, the air temperature in the mountains drops rapidly with altitude. In winter, when cold air masses invade, the air temperature in the plains is often lower than in the mountains.

The influence of mountains on precipitation is great. Precipitation increases on windward slopes and at some distance in front of them, and decreases on leeward slopes. For example, the differences in annual precipitation between the western and eastern slopes of the Ural Mountains in some places reach 300 mm. In the mountains, precipitation increases with height up to a certain critical level. In the Alps, the level of the greatest amount of precipitation falls at an altitude of about 2000 m, in the Caucasus - 2500 m.

Subtropical climate zone

Continental subtropical climate determined by the seasonal change of temperate and tropical air. The average temperature of the coldest month in Central Asia is below zero in some places, in the northeast of China -5 ...- 10 ° С. The average temperature of the warmest month is in the range of 25-30 ° С, while daily highs can exceed 40-45 ° С.

The most strongly continental climate in the air temperature regime is manifested in the southern regions of Mongolia and in the north of China, where the center of the Asian anticyclone is located in the winter season. Here, the annual amplitude of air temperature is 35-40 ° С.

Sharply continental climate in the subtropical zone for the highland regions of the Pamirs and Tibet, the height of which is 3.5-4 km. The climate of the Pamirs and Tibet is characterized by cold winters, cool summers and low rainfall.

In North America, a continental arid subtropical climate is formed in closed plateaus and intermontane basins located between the Coastal and Rocky ridges. Summers are hot and dry, especially in the south, where the average July temperature is above 30 ° C. The absolute maximum temperature can reach 50 ° C and above. In Death Valley, a temperature of +56.7 ° C was recorded!

Humid subtropical climate characteristic of the eastern coasts of the continents to the north and south of the tropics. The main areas of distribution are the southeastern United States, some southeastern regions of Europe, northern India and Myanmar, eastern China and southern Japan, northeastern Argentina, Uruguay and southern Brazil, the coast of Natal province in South Africa and the east coast of Australia. Summers in the humid subtropics are long and hot, with the same temperatures as in the tropics. The average temperature of the warmest month exceeds +27 ° С, and the maximum temperature is +38 ° С. Winters are mild, with average monthly temperatures above 0 ° C, but occasional frosts have a detrimental effect on vegetable and citrus plantations. In humid subtropics, the average annual precipitation ranges from 750 to 2000 mm, the distribution of precipitation over the seasons is quite even. In winter, rains and occasional snowfalls are brought mainly by cyclones. In summer, precipitation falls mainly in the form of thunderstorms associated with powerful inflows of warm and humid oceanic air, characteristic of the monsoon circulation of East Asia. Hurricanes (or typhoons) occur in late summer and fall, especially in the Northern Hemisphere.

Subtropical climate with dry summers typical of the western coasts of the continents north and south of the tropics. In southern Europe and North Africa, such climatic conditions are typical for the coasts Mediterranean Sea, which was the reason to call this climate also Mediterranean. A similar climate in southern California, central Chile, in the extreme south of Africa and in several areas in southern Australia. All these areas have hot summers and mild winters. As in the humid subtropics, there are occasional frosts in winter. Inland temperatures are much higher in summer than on coasts and are often the same as in tropical deserts. In general, clear weather prevails. Fogs are common on the coasts near which ocean currents pass in summer. For example, in San Francisco, summers are cool, foggy, and the most warm month- September. The maximum precipitation is associated with the passage of cyclones in winter, when the prevailing air currents mix towards the equator. The influence of anticyclones and downdrafts over the oceans are responsible for the dryness of the summer season. The average annual precipitation in a subtropical climate ranges from 380 to 900 mm and reaches its maximum values ​​on the coasts and slopes of the mountains. In summer, there is usually not enough rainfall for the normal growth of trees, and therefore a specific type of evergreen shrub vegetation develops there, known as maquis, chaparral, mal and, macchia and finbosh.

Equatorial climate zone

Equatorial type of climate circulated in equatorial latitudes in the Amazon basins in South America and the Congo in Africa, on the Malacca Peninsula and on the islands of Southeast Asia. Usually average annual temperature about +26 ° C. Due to the high noon standing of the Sun above the horizon and the same day length throughout the year, seasonal temperature fluctuations are small. Humid air, cloudiness and dense vegetation prevent nighttime cooling and maintain maximum daytime temperatures below +37 ° C, lower than in higher latitudes. Average annual rainfall in the humid tropics ranges from 1,500 to 3,000 mm and is usually evenly distributed over the seasons. Precipitation is mainly associated with the intertropical convergence zone, which is located slightly north of the equator. Seasonal displacements of this zone to the north and south in some areas lead to the formation of two maximum precipitation during the year, separated by drier periods. Thousands of thunderstorms roll over the humid tropics every day. In between, the sun shines in full force.

The Earth's climate has a large number of patterns and is formed under the influence of many factors. At the same time, it is fair to refer to it a variety of phenomena in the atmosphere. The climatic state of our planet largely determines the state of the natural environment and human activities, especially economic.

The climatic conditions of the Earth are formed by three large-scale geophysical processes of a cyclic type:

• Heat turnover- the exchange of heat between the earth's surface and the atmosphere.
• Moisture turnover- the intensity of water evaporation into the atmosphere and its correlation with the level of precipitation.
• General atmospheric circulation- a set of air currents over the Earth. The state of the troposphere is determined by the peculiarities of the distribution of air masses, for which cyclones and anticyclones are responsible. The circulation of the atmosphere occurs due to the unequal distribution of atmospheric pressure, which is due to the division of the planet into land and water bodies, as well as uneven access to ultraviolet light. The intensity of the sun's rays is determined not only by geographic features, but also by the proximity of the ocean and the frequency of precipitation.

Climate is to be distinguished from weather, which is the current state of the environment. However, weather characteristics are often the subject of climatological studies or even the most important factors in changing the Earth's climate. The level of heat plays a special role in the development of the earth's climate, as well as weather conditions. Also, the climate is influenced by sea currents and relief features, in particular - the proximity of mountain ranges. An equally important role belongs to the prevailing winds: warm or cold.

In the study of the Earth's climate, careful attention is paid to such meteorological events like atmospheric pressure, relative humidity, wind parameters, temperature indicators, precipitation. They also try to take into account solar radiation in drawing up a general planetary picture.

Climate-forming factors

1. Astronomical factors: the brightness of the Sun, the ratio of the Sun and the Earth, features of the orbits, the density of matter in space. These factors affect the level of solar radiation on our planet, daily weather changes, and the spread of heat between hemispheres.
2. Geographic factors: weight and parameters of the Earth, gravity, air components, mass of the atmosphere, currents in the ocean, the nature of the terrestrial relief, sea level, etc. These features determine the level of heat received in accordance with the weather season, continent and hemisphere of the earth.

The Industrial Revolution led to the inclusion of active human activity... Nevertheless, all characteristics of the Earth's climate are largely influenced by the energy of the Sun and the angle of incidence of ultraviolet rays.

Climate types of the Earth

There are many classifications of the planet's climatic zones. Various researchers take as a basis for the division, both individual characteristics and the general circulation of the atmosphere or a geographical component. Most often, the basis for distinguishing a separate type of climate is the solar climate - the influx of solar radiation. The proximity of water bodies and the ratio of land to sea are also important.

The simplest classification identifies 4 base belts in each earthly hemisphere:

• equatorial;
• tropical;
• moderate;
• polar.

There are transition areas between the main zones. They bear the same names, but with the prefix "sub". The first two climates, together with the transitions, can be called hot. At the same time, there is a lot of precipitation in the equatorial one. The temperate climate has more pronounced seasonal differences, especially in the case of temperature. As for the cold climatic zone, these are the most severe conditions caused by the lack of solar heat and water vapor.

This division takes into account atmospheric circulation... According to the prevalence of air masses, it is easier to divide the climate into oceanic, continental, as well as the climate of the eastern or western coasts. Some researchers define continental, maritime and monsoon climate additionally. Often in climatology there are descriptions of mountainous, arid, nival and humid climates.

Ozone layer

This concept means a layer of the stratosphere with elevated level ozone, which is formed due to the effect of sunlight on molecular oxygen. Due to the absorption of ultraviolet radiation by atmospheric ozone, the living world is protected from combustion and widespread cancer. Without the ozone layer, which appeared 500 million years ago, the first organisms would not have been able to leave the water.

Since the second half of the 20th century, it has been customary to talk about the problem of the "ozone hole" - a local decrease in the concentration of ozone in the atmosphere. The main factor of this change is of anthropogenic nature. The ozone hole can lead to increased mortality of living organisms.

Global changes in the Earth's climate

(Average air temperature rise over the past century, starting in the 1900s)

Some scientists consider large-scale climate transformations as natural process... Others believe that this is a harbinger of a global catastrophe. Such changes mean a strong warming up of air masses, an increase in aridity and a softening of winters. Also it comes about frequent hurricanes, typhoons, floods and droughts. Climate change is caused by the instability of the Sun, which leads to magnetic storms. Changes in the earth's orbit, the outlines of the oceans and continents, and volcanic eruptions also play a role. The greenhouse effect is also often associated with destructive human activities, namely: air pollution, deforestation, land plowing, and fuel combustion.

Global warming

(Climate change towards warming in the second half of the 20th century)

An increase in the average temperature of the Earth has been recorded since the second half of the 20th century. Scientists believe this is due to high levels of greenhouse gases due to human activity. The consequence of an increase in global temperature is a change in precipitation, an increase in deserts, an increase in the frequency of extreme weather phenomena extinction of some biological species, sea level rise. Worst of all, in the Arctic, this is causing glaciers to shrink. Together, this can radically change the habitat of various animals and plants, shift the boundaries of natural zones and cause serious problems with agriculture and human immunity.

On Earth, it determines the character of many features of nature. Climatic conditions also strongly affect the life, economic activity of people, their health and even biological characteristics. At the same time, the climates of individual territories do not exist in isolation. They are parts of the atmospheric process that is common for the entire planet.

Climate classification

The Earth's climates, which have features of similarity, are combined into certain types, which replace each other in the direction from the equator to the poles. In each hemisphere, there are 7 climatic zones, of which 4 are main and 3 are transitional. This division is based on the placement of air masses over the globe with different properties and the peculiarities of air movement in them.

One air mass is formed in the main zones throughout the year. In the equatorial belt - equatorial, in the tropical - tropical, in the temperate - the air of temperate latitudes, in the arctic (Antarctic) - arctic (Antarctic). In the transition belts located between the main ones, in different seasons years, air masses come in from the adjacent main belts in turn. Here, the conditions change according to the seasons: in summer they are the same as in the neighboring warmer zone, in winter they are the same as in the neighboring colder one. Along with the change in air masses in the transition zones, the weather also changes. For example, in subequatorial belt hot and rainy weather prevails in summer and cooler and drier in winter.

The climate within the belts is not uniform. Therefore, the belts are divided into climatic regions. Above the oceans, where sea air masses are formed, there are areas of oceanic climates, and above the continents - continental. In many climatic zones on the western and eastern coasts of the continents, special types of climate are formed that differ from both continental and oceanic ones. The reason for this is the interaction of sea and continental air masses, as well as the presence of ocean currents.

Roasts include and. These territories constantly receive a significant amount of heat due to the large angle of incidence of sunlight.

The equatorial belt is dominated by the equatorial air mass throughout the year. The heated air in low pressure conditions constantly rises, which leads to the formation of rain clouds. There are heavy rainfalls every day, often from. The amount of precipitation is 1000-3000 mm per year. This is more than moisture can evaporate. The equatorial zone has one season of the year: it is always hot and humid.

In tropical zones, tropical air mass dominates throughout the year. In it, air descends from the upper layers of the troposphere to the earth's surface. As it sinks, it heats up, and even over the oceans, no clouds form. Clear weather prevails, in which the sun's rays strongly heat the surface. Therefore, on land, the average in summer is higher than in the equatorial zone (up to +35 ° WITH). Winter temperatures are lower than summer temperatures due to a decrease in the angle of incidence of sunlight. Due to the absence of clouds throughout the year, there is very little rainfall, so tropical deserts are common on land. These are the hottest areas of the Earth with temperature records. The exception is the eastern shores of the continents, which are washed by warm currents and are under the influence of trade winds blowing from the oceans. Therefore, a lot of precipitation falls here.

The territory of subequatorial (transitional) zones is occupied by humid equatorial air mass in summer, and dry tropical air mass in winter. Therefore, here there are hot and rainy summers and dry and also hot - due to the high standing of the Sun - winter.

Moderate climatic zones

They occupy about 1/4 of the Earth's surface. They have sharper seasonal differences in temperature and precipitation than hot zones. This is due to a significant decrease in the value of the angle of incidence of the sun's rays and the complication of circulation. They contain the air of temperate latitudes all year round, but frequent intrusions of arctic and tropical air are noted.

The Southern Hemisphere is dominated by an oceanic temperate climate with cool summers (from +12 to +14 ° C), mild winters (from +4 to +6 ° C) and abundant precipitation (about 1000 mm per year). In the Northern Hemisphere, large areas are occupied by the continental temperate and. His main feature- pronounced temperature changes over the seasons.

On the western shores of the continents, humid air from the oceans, brought by westerly winds of temperate latitudes, comes all year round, there is a lot of precipitation here (1000 mm per year). Summers are cool (up to + 16 ° С) and humid, and winters are humid and warm (from 0 to + 5 ° С). In the direction from west to east inland, the climate becomes more continental: the amount of precipitation decreases, summer temperatures increase, and winter temperatures decrease.

A monsoon climate is formed on the eastern shores of the continents: summer monsoons bring heavy rainfall from the oceans, and frosty and drier weather is associated with winter ones blowing from continents to oceans.

In the subtropical transition zones, temperate air comes in winter, and tropical air in summer. The continental subtropical climate is characterized by hot (up to + 30 ° С) dry summers and cool (from 0 to + 5 ° С) and slightly more humid winters. There is less precipitation per year than it can evaporate, so deserts and semi-deserts prevail. There is a lot of precipitation on the coasts of the continents, and on the western shores it is rainy in winter due to westerly winds from the oceans, and on the east - in summer due to monsoons.

Cold climatic zones

The earth's surface receives little solar heat during the polar day, and does not heat up at all during the polar night. Therefore, the Arctic and Antarctic air masses are very cold and contain little. The Antarctic continental climate is the most severe: exceptionally frosty winter and cold summers with freezing temperatures. Therefore, it is covered with a powerful glacier. In the Northern Hemisphere, a similar climate is in, and above - marine arctic. It is warmer than the Antarctic, since the ocean waters, even covered with ice, provide additional heat.

In the subarctic and subantarctic belts, the arctic (Antarctic) air mass dominates in winter, and the air of temperate latitudes in summer. Summers are cool, short and humid, winters are long, severe and with little snow.

1. The concept of climate.Climate- this is a long-term weather regime typical for a given area. It, like weather, is characterized by a set of values ​​of meteorological elements. The main ones are temperature and precipitation, their changes throughout the year. Data for scientific generalization are taken over a multi-year period (usually 35 or 100 years). The description of the climate includes not only the average values ​​of meteorological elements, but also their annual and daily variations, extreme values, and frequency.

The climate, in contrast to the weather, is characterized by stability. It changes only for a very long time. However, climate fluctuations can be observed for a shorter time (for example, 30-35 years). The climate, like all meteorological elements, changes on the earth's surface from the equator to the poles, and at the same latitude - when moving from the coasts of the continents to their inland parts. V mountainous countries climatic conditions vary from the foothills to the tops of the mountains.

The climate is very important for the processes occurring on the earth's surface. It has a great influence on the destruction of rocks and relief, the nutrition of rivers and reservoirs, their condition, and the development of soils. The richness of flora and fauna is also determined by the climate. Climatic conditions affect human health and lifestyle.

In the modern period, humans and their economic activities have a great impact on the climate (Fig. 34, 35). The consequences affect the natural conditions of human life (Fig. 36).

2. Dependence of the climate on the geographical latitude and remoteness of the territory from the oceans and seas. The main factors of climate formation are geographic latitude; land and ocean distribution; remoteness of the territory from the seas and oceans; sea ​​currents; height above sea level; relief. They're called climate-forming factors(fig. 37).

The main climate-forming factor is latitude. Basically, the amount of solar heat that the earth's surface receives depends on it. Therefore, the air temperature changes from the equator to the poles. All other meteorological elements (atmospheric pressure, winds, humidity, cloudiness, precipitation) and the climate in general change in this direction.

Important climate-forming factors are the distribution of land and sea and the remoteness of the territory from seas and oceans (Fig. 38). Land and sea are heated and cooled in different ways. Therefore, at the same latitude, there are significant differences in temperature and precipitation distribution. So, at a parallel of 60 ° N. NS. the average January temperature in the Atlantic Ocean and near the western coasts of Europe is 0 ° C. Near the eastern shores of the Baltic Sea, it is -8 ° С, in the east of the East European Plain - -14 ° С, on the Yenisei - -30 ° С, on the Lena - -40 ° С. The amount of precipitation decreases in the same direction. In the west of Europe, they fall over 1000 mm, in the East European Plain - about 500 mm, in the east of Siberia - 300 mm.

There are no less differences in temperature amplitudes, pressure, character and time of precipitation. Therefore, a distinction is made between maritime and continental climates.

3. Sea currents and climate. Sea currents have a great influence on the climate. They transfer heat from one latitude to another and lead to a cooling or warming of the climate. The coasts of the continents, washed by cold currents, are colder than their inner parts located at the same latitudes. Cold currents increase the dryness of the climate. They cool the lower layers of the air, and cold air is known to become denser and heavier and cannot rise. This does not contribute to the formation of clouds and precipitation. The climate of the coasts washed by warm currents is warmer and milder than inland. From warm currents, the air is heated and humidified. When it rises up, it becomes oversaturated, clouds form, precipitation falls.

An example of the different influence on the climate of warm and cold currents is the climate of the east coast of North America and the west coast of Europe between the 55th and 70th parallels. The American coast is washed by the cold Labrador Current, and the European coast is washed by the warm North Atlantic. On the American coast, the average annual temperatures are from 0 to -10 ° С, on the European coast - from +10 to 0 ° С. The frost-free period on the American coast lasts 60 days a year, and on the European coast - from 150 to 210 days. On the Labrador Peninsula there are treeless areas, in Europe there are coniferous and mixed forests.

4. Relief and climate. The influence of the relief on the climate is great and varied. Mountain rises and ridges are mechanical barriers to the movement of air. In some cases, mountains are the border of regions with different climates, because they impede the exchange of air. Thus, the dryness of the climate in the central part of Asia is largely due to the presence of large mountain systems on its outskirts.

The location of mountain slopes and ridges in relation to the oceans and the sides of the horizon causes different distribution of precipitation. The windward slopes of the mountains receive more precipitation than the leeward ones, since the air, when it rises along the slopes of the mountains, cools, becomes oversaturated and emits abundant precipitation (Fig. 39). It is on the windward slopes of mountainous countries that the wettest regions of the Earth are located. For example, a lot of precipitation falls on the southern slopes of the Himalayas, so there is a rich flora and fauna. The northern slopes of the Himalayas are dry and deserted.

Climatic conditions in the mountains depend on the absolute height. With altitude, the air temperature decreases, atmospheric pressure and humidity fall, the amount of precipitation to a certain height increases and then decreases, the speed and direction of the wind change. The climate in the mountains changes over relatively short distances and differs significantly from the climate of the neighboring plains.

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CLIMATE, long-term weather regime in a given area. The weather at any given time is characterized by certain combinations of temperature, humidity, wind direction and speed. In some types of climates, the weather changes significantly every day or according to seasons, in others it remains unchanged. Climatic descriptions are based on statistical analysis of average and extreme meteorological characteristics. As a factor of the natural environment, climate affects the geographical distribution of vegetation, soils and water resources and therefore on land use and economics. Climate also affects human living conditions and health.

Climatology is the science of climate that studies the reasons for the formation of different types of climate, their geographical location and the relationship of climate and others natural phenomena... Climatology is closely related to meteorology, a branch of physics that studies the short-term states of the atmosphere, i.e. the weather.

CLIMATE FORMING FACTORS

Position of the Earth.

When the Earth revolves around the Sun, the angle between the polar axis and the perpendicular to the orbital plane remains constant and is 23 ° 30ў. This movement explains the change in the angle of incidence of sunlight on the earth's surface at noon at a certain latitude during the year. The greater the angle of incidence of the sun's rays on the Earth in this place, the more efficiently the Sun heats the surface. Only between the Northern and Southern tropics (from 23 ° 30ў N to 23 ° 30ў S) do the sun's rays fall vertically on the Earth at certain times of the year, and here the Sun always rises high above the horizon at noon. Therefore, in the tropics it is usually warm at any time of the year. At higher latitudes, where the Sun is lower above the horizon, the heating of the earth's surface is less. There are significant seasonal changes in temperature (which does not happen in the tropics), and in winter the angle of incidence of sunlight is relatively small and the days are much shorter. At the equator, day and night always have equal duration, while at the poles, day lasts the entire summer half of the year, and in winter the Sun never rises above the horizon. The length of the polar day only partially compensates for the low standing of the Sun above the horizon, and as a result, the summer is cool here. In dark winters, the polar regions quickly lose heat and become very cool.

Distribution of land and sea.

Water heats up and cools more slowly than dry land. Therefore, the air temperature over the oceans has less daily and seasonal changes than over the continents. In coastal areas, where winds blow from the sea, summers are generally cooler and winters warmer than in the interior of the continents at the same latitude. The climate of such windward coasts is called maritime. The interior regions of the continents in temperate latitudes are characterized by significant differences in summer and winter temperatures. In such cases, they speak of a continental climate.

Water areas are the main source of atmospheric moisture. When winds blow from the warm oceans onto land, there is a lot of rainfall. Windward coasts tend to be more humid and cloudy and more days with fogs than in inland regions.

Circulation of the atmosphere.

The nature of the baric field and the rotation of the Earth determine the general circulation of the atmosphere, due to which heat and moisture are constantly redistributed over the earth's surface. Winds blow from high pressure areas to low pressure areas. High pressure is usually associated with cold, dense air, while low pressure is associated with warm, less dense air. The rotation of the Earth causes air currents to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This deviation is called the Coriolis effect.

In both the Northern and Southern Hemispheres, there are three main wind zones in the surface layers of the atmosphere. In the intertropical convergence zone at the equator, the northeastern trade wind approaches the southeastern trade wind. Tradewinds originate in high-pressure subtropical regions, most developed over the oceans. Air currents, moving towards the poles and deflected by the Coriolis force, form the predominant westerly transport. In the region of polar fronts of temperate latitudes, the western transport meets the cold air of high latitudes, forming a zone of baric systems with low pressure in the center (cyclones) moving from west to east. Although the air currents in the polar regions are not so pronounced, the polar eastward transport is sometimes distinguished. These winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. Cold air masses often penetrate temperate latitudes.

Winds in areas of convergence of air currents form ascending air currents, which cools with height. In this case, the formation of clouds is possible, often accompanied by precipitation. Therefore, in the intertropical convergence zone and frontal zones in the belt of the predominant western transport, there is a lot of precipitation.

Winds blowing in the higher layers of the atmosphere close the circulation system in both hemispheres. The air that rises upward in the convergence zones rushes into the high-pressure area and descends there. At the same time, with increasing pressure, it heats up, which leads to the formation of a dry climate, especially on land. These downdrafts define the climate of the Sahara, located in the subtropical high-pressure belt in North Africa.

Seasonal changes in heating and cooling determine seasonal movements of the main baric formations and wind systems. Wind zones in summer shift towards the poles, which leads to changes in weather conditions at a given latitude. So, for the African savannas, covered with grassy vegetation with sparsely growing trees, rainy summers (due to the influence of the intertropical convergence zone) and dry winters are characteristic, when a high-pressure area with downgrading air flows into this territory.

The seasonal changes in the general circulation of the atmosphere are also influenced by the distribution of land and sea. In the summer, when the Asian mainland warms up and a lower pressure area is established over it than over the surrounding oceans, the coastal southern and southeastern regions are affected by moist air currents directed from the sea to the land and bringing abundant rains. In winter, air flows from the cold surface of the mainland to the oceans, and much less rain falls. Such winds, which change direction to the opposite depending on the season, are called monsoons.

Ocean currents

are formed under the influence of near-surface winds and differences in water density due to changes in its salinity and temperature. The direction of currents is influenced by the Coriolis force, the shape of the sea basins and the outlines of the coast. In general, the circulation of ocean currents is similar to the distribution of air currents over the oceans and occurs clockwise in the Northern Hemisphere and counterclockwise in the Southern.

Crossing heading towards the poles warm currents, the air becomes warmer and more humid and has a corresponding effect on the climate. Ocean currents heading towards the equator carry cool waters. Passing along the western outskirts of the continents, they lower the temperature and moisture content of the air, and, accordingly, the climate under their influence becomes cooler and drier. Due to the condensation of moisture near the cold sea surface, fog often occurs in such areas.

The relief of the earth's surface.

Large landforms have a significant impact on the climate, which changes depending on the height of the terrain and in the interaction of air currents with orographic obstacles. The air temperature usually decreases with height, which leads to the formation of a cooler climate in the mountains and on the plateau than in the adjacent lowlands. In addition, hills and mountains form obstacles that force the air to rise and expand. As it expands, it cools. This cooling, called adiabatic cooling, often results in moisture condensation and the formation of clouds and precipitation. Most of the precipitation due to the barrier effect of mountains falls on their upwind side, while the leeward side remains in the "rain shadow". Air descending on leeward slopes heats up when compressed, forming a warm, dry wind known as a hair dryer.

CLIMATE AND LATITUDE

In climatic surveys of the Earth, it is advisable to consider latitudinal zones. The distribution of climatic zones in the Northern and Southern Hemispheres is symmetrical. North and south of the equator are tropical, subtropical, temperate, subpolar and polar zones. The baric fields and zones of prevailing winds are also symmetrical. Consequently, most of the climate types in one hemisphere can be found at similar latitudes in the other hemisphere.

MAIN CLIMATE TYPES

Climate classification provides an ordered system for characterizing climate types, their regionalization and mapping. The types of climate that prevail over large areas are called macroclimates. A macroclimatic region should have more or less homogeneous climatic conditions that distinguish it from other regions, although it is only a generalized characteristic (since there are no two places with an identical climate), more consistent with realities than the allocation of climatic regions only on the basis of belonging to a certain latitudinal -the geographical belt.

Ice sheet climate

dominates in Greenland and Antarctica, where average monthly temperatures are below 0 ° C. In the dark winter season, these regions do not receive solar radiation at all, although there are twilight and auroras. Even in summer, the sun's rays fall on the earth's surface at a slight angle, which reduces the heating efficiency. Most of the incoming solar radiation is reflected by ice. Both summer and winter, the elevated regions of the Antarctic Ice Sheet are characterized by low temperatures. The climate of the interior regions of Antarctica is much colder than the climate of the Arctic, since the southern continent is large and high, and the Arctic Ocean softens the climate, despite the widespread distribution of pack ice. In summer, during short warmings, drifting ice sometimes melts.

Precipitation on ice sheets falls in the form of snow or small particles of ice fog. The interior regions receive only 50–125 mm of precipitation annually, but more than 500 mm can fall on the coast. Sometimes cyclones bring clouds and snow to these areas. Snowfalls are often accompanied by strong winds that carry significant amounts of snow, blowing it off the rocks. Strong katabatic winds with blizzards blow from the cold ice sheet, carrying snow to the coast.

Subpolar climate

manifests itself in the tundra regions on the northern outskirts of North America and Eurasia, as well as on the Antarctic Peninsula and adjacent islands. In eastern Canada and Siberia southern border of this climatic zone passes significantly south of the Arctic Circle due to the strongly pronounced influence of vast land masses. This leads to long and extremely cold winters. Summers are short and cool, with average monthly temperatures rarely exceeding + 10 ° C. To some extent, long days compensate for the short summer duration, but in most of the territory, the heat received is not enough to completely thaw the soil. Permafrost soil, called permafrost, inhibits plant growth and the filtration of melt water into the soil. Therefore, in summer, flat areas turn out to be swampy. On the coast, winter temperatures are slightly higher, and summer temperatures are slightly lower than in the interior regions of the mainland. In summer, when humid air is above cold water or sea ice, fog often occurs on the Arctic coasts.

Annual precipitation usually does not exceed 380 mm. Most of them fall in the form of rain or snow in the summer, during the passage of cyclones. On the coast, most of the precipitation can be brought by winter cyclones. However, the low temperatures and clear weather of the cold season, typical for most areas with a subpolar climate, are unfavorable for significant snow accumulation.

Subarctic climate

It is also known under the name "taiga climate" (according to the prevailing type of vegetation - coniferous forests). This climatic zone covers the temperate latitudes of the Northern Hemisphere - the northern regions of North America and Eurasia, located immediately south of the subpolar climate zone. Sharp seasonal climatic differences are manifested here due to the position of this climatic zone in rather high latitudes in the inner parts of the continents. Winters are long and extremely cold, and the farther north, the shorter the days. Summers are short and cool with long days. In winter, the period with negative temperatures is very long, and in summer the temperature at times can exceed + 32 ° C. In Yakutsk, the average temperature in January is –43 ° С, in July - + 19 ° С, i.e. the annual temperature range reaches 62 ° C. A milder climate is typical for coastal areas, such as southern Alaska or northern Scandinavia.

Most of the climatic zone under consideration receives less than 500 mm of precipitation per year, with the maximum amount on the windward coasts and minimum in the inner part of Siberia. There is very little snowfall in winter, snowfalls are associated with rare cyclones. Summers are usually more humid, with rain falling mainly when passing atmospheric fronts... Fogs and overcast clouds are common on the coasts. In winter, in severe frosts over snow cover ice fogs hang.

Humid continental climate with short summers

characteristic of a vast strip of temperate latitudes of the Northern Hemisphere. In North America, it stretches from the prairies in southern central Canada to the Atlantic coast, and in Eurasia it covers most of of Eastern Europe and some areas Central Siberia... The same type of climate is observed in the Japanese island of Hokkaido and in the south of the Far East. The main climatic features of these regions are determined by the prevailing westerly transport and the frequent passage of atmospheric fronts. V harsh winters average air temperatures can drop to –18 ° C. Summers are short and cool, with a frost-free period of less than 150 days. The annual temperature range is not as large as under conditions subarctic climate... In Moscow, the average temperatures in January are –9 ° С, in July - + 18 ° С.In this climatic zone, there is a constant threat to Agriculture represent spring frosts. In the coastal provinces of Canada, in New England and on about. Hokkaido winters are warmer than inland areas, as the easterly winds bring in warmer ocean air at times.

Annual precipitation ranges from less than 500 mm in the interior of the continents to over 1000 mm on the coasts. In most of the region, precipitation falls mainly in summer, often during thunderstorm showers. Winter precipitation, mainly in the form of snow, is associated with the passage of fronts in cyclones. Blizzards are often seen in the rear of the cold front.

Humid continental climate with long summers.

Air temperatures and the length of the summer season increase southward in humid continental climates. This type of climate is manifested in the temperate latitudinal belt of North America from the eastern Great Plains to the Atlantic coast, and in southeastern Europe - in the lower reaches of the Danube. Similar climatic conditions are also expressed in northeastern China and central Japan. It is also dominated by the western transfer. The average temperature of the warmest month is + 22 ° С (but temperatures can exceed + 38 ° С), summer nights are warm. Winters are not as cold as in humid continental climates with short summers, but temperatures sometimes drop below 0 ° C. The annual temperature range is usually 28 ° C, as, for example, in Peoria, Illinois, USA, where the average temperature in January –4 ° С, and in July - + 24 ° С. On the coast, the annual temperature amplitudes decrease.

Most often in a humid continental climate with long summer falls from 500 to 1100 mm of precipitation per year. The greatest amount of precipitation is brought by summer thunderstorms during the growing season. In winter, rains and snowfalls are mainly associated with the passage of cyclones and associated fronts.

Temperate maritime climate

inherent in the western coasts of the continents, primarily in northwestern Europe, the central part of the Pacific coast of North America, southern Chile, southeastern Australia and New Zealand. The prevailing westerly winds blowing from the oceans have a softening effect on the course of air temperature. Winters are mild with average temperatures of the coldest month above 0 ° C, but when the Arctic air currents reach the coasts, there are also frosts. Summers are generally quite warm; with intrusions of continental air during the day, the temperature can rise for a short time to + 38 ° C. This type of climate with a small annual temperature amplitude is the most temperate among climates of temperate latitudes. For example, in Paris, the average temperature in January is + 3 ° С, in July - + 18 ° С.

In areas of a temperate maritime climate, the average annual precipitation ranges from 500 to 2500 mm. The most humidified are the windward slopes of the coastal mountains. In many areas, rainfall occurs fairly evenly throughout the year, with the exception of the Pacific Northwest coast of the United States, which has very wet winters. Cyclones moving from the oceans bring a lot of precipitation to the western continental outskirts. In winter, as a rule, it keeps cloudy weather with light rains and occasional short-term snowfalls. Fogs are common on the coasts, especially in summer and autumn.

Humid subtropical climate

characteristic of the eastern coasts of the continents to the north and south of the tropics. The main areas of distribution are the southeastern United States, some southeastern regions of Europe, northern India and Myanmar, eastern China and southern Japan, northeastern Argentina, Uruguay and southern Brazil, the coast of Natal province in South Africa and the east coast of Australia. Summers in the humid subtropics are long and hot, with the same temperatures as in the tropics. The average temperature of the warmest month exceeds + 27 ° C, and the maximum is + 38 ° C. Winters are mild, with average monthly temperatures above 0 ° C, but occasional frosts have a detrimental effect on vegetable and citrus plantations.

In humid subtropics, the average annual precipitation ranges from 750 to 2000 mm, the distribution of precipitation over the seasons is quite even. In winter, rains and occasional snowfalls are brought mainly by cyclones. In summer, precipitation falls mainly in the form of thunderstorms associated with powerful inflows of warm and humid oceanic air characteristic of the monsoon circulation. East Asia... Hurricanes (or typhoons) occur in late summer and fall, especially in the Northern Hemisphere.

Subtropical climate with dry summers

typical of the western coasts of the continents north and south of the tropics. In southern Europe and North Africa, such climatic conditions are typical for the Mediterranean coasts, which is why this climate is also called Mediterranean. The climate is the same in southern California, central Chile, in the extreme south of Africa and in several areas in southern Australia. All these areas have hot summers and mild winters. As in the humid subtropics, there are occasional frosts in winter. Inland temperatures are much higher in summer than on coasts and are often the same as in tropical deserts. In general, clear weather prevails. Fogs are common on the coasts near which ocean currents pass in summer. For example, in San Francisco, summers are cool, foggy, and the warmest month is September.

The maximum precipitation is associated with the passage of cyclones in winter, when the prevailing western air currents are shifted towards the equator. The influence of anticyclones and downdrafts under the oceans are responsible for the dryness of the summer season. The average annual precipitation in a subtropical climate ranges from 380 to 900 mm and reaches its maximum values ​​on the coasts and slopes of the mountains. In summer, there is usually not enough rainfall for the normal growth of trees, and therefore a specific type of evergreen shrub vegetation develops there, known as maquis, chaparral, mali, macchia and finbosh.

Semi-arid climate of temperate latitudes

(synonym - steppe climate) is typical mainly for inland regions, remote from the oceans - sources of moisture - and usually located in the rain shadow of high mountains. The main regions with a semiarid climate are the intermontane basins and the Great Plains of North America and the steppes of central Eurasia. Hot summers and cold winters are due to the inland position in temperate latitudes. At least one winter month has an average temperature below 0 ° C, and the average temperature of the warmest summer month exceeds + 21 ° C. The temperature regime and the duration of the frost-free period vary significantly depending on latitude.

The term "semi-arid" is used to characterize this climate because it is less dry than the arid climate itself. The average annual precipitation is usually less than 500 mm, but more than 250 mm. Since the development of steppe vegetation in conditions of higher temperatures requires more precipitation, the latitudinal-geographical and altitude position of the area is determined by climatic changes. For a semiarid climate, there are no general patterns of precipitation distribution throughout the year. For example, in areas bordering the subtropics with dry summers, the maximum precipitation is observed in winter, while in areas adjacent to areas of humid continental climate, it rains mainly in summer. Cyclones in temperate latitudes bring most of the winter precipitation, which often falls as snow and can be accompanied by strong winds. Summer thunderstorms are not uncommon with hail. The amount of precipitation varies greatly from year to year.

Arid climate of temperate latitudes

is inherent mainly in the Central Asian deserts, and in the west of the United States - only in small areas in intermontane basins. The temperatures are the same as in regions with a semi-arid climate, however, there is not enough rainfall for the existence of a closed natural vegetation cover, and the average annual amounts usually do not exceed 250 mm. As in semiarid climatic conditions, the amount of precipitation, which determines the aridity, depends on the thermal regime.

Semi-arid climate of low latitudes

mostly typical for the outskirts tropical deserts(for example, the Sahara and the deserts of central Australia), where downdrafts in subtropical high pressure zones exclude precipitation. The climate in question differs from the semiarid climate of temperate latitudes in very hot summers and warm winter... Average monthly temperatures are above 0 ° C, although frosts sometimes occur in winter, especially in areas farthest from the equator and located at high altitudes. The amount of precipitation required for the existence of closed natural herbaceous vegetation is higher here than in temperate latitudes. In the equatorial zone, it rains mainly in summer, while on the outer (northern and southern) outskirts of deserts, the maximum precipitation occurs in winter. Most of the precipitation falls in the form of thunderstorms, and in winter it is brought in by cyclones.

Arid climate of low latitudes.

It is a hot, dry climate of tropical deserts that stretch along the Northern and Southern tropics and are influenced by subtropical anticyclones for most of the year. Salvation from the sweltering summer heat can be found only on the coasts washed by cold ocean currents, or in the mountains. On the plains, the average summer temperatures noticeably exceed + 32 ° C, winter temperatures are usually above + 10 ° C.

In most of this climatic region, the average annual precipitation does not exceed 125 mm. It so happens that precipitation has not been recorded at all at many meteorological stations for several years in a row. Sometimes the average annual precipitation can reach 380 mm, but this is still enough only for the development of sparse desert vegetation. Occasionally precipitation falls in the form of short, strong thunderstorms, but the water drains quickly, forming flash floods. The driest areas are along the western coasts of South America and Africa, where cold ocean currents inhibit cloud formation and precipitation. Fogs are common on these coasts, formed by condensation of moisture in the air over the colder ocean surface.

Variably humid tropical climate.

Regions with such a climate are located in tropical sublatitudinal zones, several degrees north and south of the equator. This climate is also called monsoon tropical, as it prevails in those parts of South Asia that are influenced by monsoons. Other regions with such a climate are the tropics of Central and South America, Africa and Northern Australia. Average summer temperatures are usually approx. + 27 ° С, and winter - approx. + 21 ° C. The hottest month, as a rule, precedes the summer rainy season.

Average annual precipitation ranges from 750 to 2000 mm. During the summer rainy season, the intertropical convergence zone has a decisive influence on the climate. Thunderstorms often occur here, sometimes overcast clouds with prolonged rains remain for a long time. Winter is dry, as subtropical anticyclones dominate this season. In some areas, it does not rain for two to three winter months. In South Asia, the wet season coincides with the summer monsoon, which brings moisture from the Indian Ocean, and in winter, Asian continental dry air masses spread here.

Humid tropical climate

or a tropical rainforest climate, common in equatorial latitudes in the Amazon basins in South America and the Congo in Africa, on the Malacca Peninsula and on the islands of Southeast Asia. In the humid tropics, the average temperature of any month is not less than + 17 ° C, usually the average monthly temperature is approx. + 26 ° C. As in the variable humid tropics, due to the high noon standing of the Sun above the horizon and the same day length throughout the year, seasonal temperature fluctuations are small. Humid air, cloudiness and dense vegetation prevent nighttime cooling and maintain maximum daytime temperatures below + 37 ° C, lower than in higher latitudes.

Average annual rainfall in the humid tropics ranges from 1500 to 2500 mm, the distribution over the seasons is usually fairly even. Precipitation is mainly associated with the intertropical convergence zone, which is located slightly north of the equator. Seasonal displacements of this zone to the north and south in some areas lead to the formation of two maximum precipitation during the year, separated by drier periods. Thousands of thunderstorms roll over the humid tropics every day. In between, the sun shines in full force.

Highland climates.

In high-mountainous regions, a significant variety of climatic conditions is due to latitudinal-geographical position, orographic barriers and different exposure of slopes in relation to the Sun and moisture-carrying air currents. Even at the equator, in the mountains, there are snowfields-migrations. The lower boundary of the eternal snow falls towards the poles, reaching sea level in the polar regions. Similarly, other boundaries of high-altitude thermal belts decrease as they approach high latitudes. The windward slopes of the mountain ranges receive more precipitation. On mountain slopes that are open to cold air intrusion, the temperature may drop. In general, the climate of the highlands is characterized by lower temperatures, higher cloudiness, more precipitation and a more complex wind regime than the climate of the plains at the corresponding latitudes. The pattern of seasonal changes in temperature and precipitation in the highlands is usually the same as in the adjacent plains.

MESO- AND MICROCLIMATES

Territories that are inferior in size to macroclimatic regions also have climatic features that deserve special study and classification. Meso-climates (from the Greek meso - medium) are climates of territories of several square kilometers, for example, wide river valleys, intermontane depressions, depressions of large lakes or cities. In terms of the area of ​​distribution and the nature of the differences, the mesoclimates are intermediate between macroclimates and microclimates. The latter characterize the climatic conditions in small areas of the earth's surface. Microclimatic observations are carried out, for example, on city streets or on test sites established within a homogeneous plant community.

EXTREME CLIMATE INDICATORS

Such climatic characteristics, like temperature and precipitation, vary over a wide range between extreme (minimum and maximum) values. Although rarely observed, extremes are as important as averages to understanding the nature of the climate. The warmest climate is in the tropics, with the tropical rainforest climate being hot and humid, and the arid climate of low latitudes hot and dry. The maximum air temperatures are noted in tropical deserts. The highest temperature in the world - + 57.8 ° С - was recorded in El-Azizia (Libya) on September 13, 1922, and the lowest - -89.2 ° С at the Soviet Vostok station in Antarctica on July 21, 1983.

Extreme values ​​of precipitation have been recorded in different parts of the world. For example, in the 12 months from August 1860 to July 1861 in the town of Cherrapunji (India), 26 461 mm fell. The average annual rainfall at this point, one of the rainiest on the planet, is approx. 12,000 mm. Less data are available on the amount of snow that fell. At Paradise Ranger Station in Mount Rainier National Park, Washington, USA, 28,500 mm of snow were recorded during the winter of 1971-1972. At many meteorological stations in the tropics with long observation records, precipitation has never been observed at all. There are many such places in the Sahara and on the west coast of South America.

At extreme wind speeds, measuring instruments (anemometers, anemographs, etc.) often failed. The highest wind speeds in the surface air layer are likely to develop in tornadoes (tornadoes), where, according to estimates, they can well exceed 800 km / h. In hurricanes or typhoons, the wind sometimes reaches speeds of over 320 km / h. Hurricanes are very common in the Caribbean and Western Pacific.

IMPACT OF CLIMATE ON BIOTA

The temperature and light conditions and moisture supply, necessary for the development of plants and limiting their geographical distribution, depend on the climate. Most plants cannot grow at temperatures below + 5 ° C, and many species die at subzero temperatures. With an increase in temperatures, the needs of plants for moisture increase. Light is essential for photosynthesis as well as for flowering and seed development. Shading the soil with tree crowns in a dense forest inhibits the growth of more low plants... An important factor is also the wind, which significantly changes the temperature and humidity regime.

The vegetation of each region is an indicator of its climate, since the distribution of plant communities is largely influenced by the climate. The vegetation of the tundra in a subpolar climate is formed only by such undersized forms as lichens, mosses, grasses and low shrubs. The short growing season and widespread permafrost make it difficult for trees to grow everywhere, except for river valleys and southern slopes, where the soil thaws to greater depths in summer. Coniferous forests of spruce, fir, pine and larch, also called taiga, grow in a subarctic climate.

Wet areas of temperate and low latitudes are especially favorable for the growth of forests. The densest forests are confined to areas of a temperate maritime climate and humid tropics. Areas of humid continental and humid subtropical climate are also mostly forested. In the presence of a dry season, for example, in areas of a subtropical climate with dry summers or a variable-humid tropical climate, plants adapt accordingly, forming either a short or sparse tree layer. So, in savannas in conditions of a variable-humid tropical climate, grasslands with single trees growing at large distances from one another predominate.

In semiarid climates of temperate and low latitudes, where everywhere (except river valleys) it is too dry for tree growth, herbaceous steppe vegetation dominates. The grains are undersized here, and an admixture of dwarf shrubs and dwarf shrubs, such as wormwood in North America, is also possible. In temperate latitudes, the grass steppes in more humid conditions at the borders of their range are replaced by tall grass prairies. In arid conditions, plants grow far from one another, often have thick bark or fleshy stems and leaves that can store moisture. The driest areas of tropical deserts are completely devoid of vegetation and are bare rocky or sandy surfaces.

The climatic altitudinal zonation in the mountains determines the corresponding vertical differentiation of vegetation - from herbaceous communities of the foothill plains to forests and alpine meadows.

Many animals are able to adapt to a wide range of climatic conditions. For example, mammals in colder climates or in winter have warmer fur. However, they also care about the availability of food and water, which varies with climate and season. Many animal species are characterized by seasonal migrations from one climatic region to another. For example, in winter, when grasses and shrubs dry up in the changing tropical climate of Africa, there are massive migrations of herbivores and predators to more humid areas.

V natural areas the earth's soil, vegetation and climate are closely intertwined. Heat and moisture determine the nature and rate of chemical, physical and biological processes, as a result of which rocks on slopes of different steepness and exposure, a huge variety of soils is created. Where the soil is frozen by permafrost for most of the year, as in the tundra or high in the mountains, the processes of soil formation are slowed down. Under arid conditions, soluble salts are usually found on the soil surface or in near-surface horizons. In humid climates, excess moisture seeps downward, carrying soluble mineral compounds and clay particles to significant depths. Some of the most fertile soils are the products of recent accumulation - wind, fluvial or volcanic. Such young soils have not yet undergone strong leaching and therefore retained their nutrient reserves.

Crop distribution and soil cultivation practices are closely related to climatic conditions. Bananas and rubber trees require an abundance of heat and moisture. Date palms grow well only in oases in arid low-latitude areas. Most crops in arid temperate and low latitudes require irrigation. A common type of land use in semiarid climates where grasses are common is grazing. Cotton and rice have a longer growing season than spring wheat or potatoes, and all of these crops suffer from frost damage. In the mountains, agricultural production is differentiated by altitude belts just like natural vegetation. Deep valleys in the humid tropics of Latin America are located in the hot zone (tierra caliente) and tropical crops are grown there. At somewhat higher altitudes in the temperate zone (tierra templada), coffee is the typical crop. Above is the cold belt (tierra fria), where crops and potatoes are grown. In an even colder zone (tierra helada), located just below the snow line, livestock grazing is possible on alpine meadows, and the range of crops is extremely limited.

The climate affects the health and living conditions of people as well as their economic activities. The human body loses heat through radiation, heat conduction, convection and evaporation of moisture from the surface of the body. If these losses are too large in cold weather or too small in hot weather, the person experiences discomfort and may get sick. Low relative humidity and high speed wind increases the cooling effect. Changes in the weather lead to stress, impair appetite, disrupt biorhythms and reduce the human body's resistance to disease. Climate also affects the habitat of disease-causing pathogens, and therefore seasonal and regional disease outbreaks occur. Pneumonia and influenza epidemics in temperate latitudes often occur in winter. Malaria is common in the tropics and subtropics, where there are conditions for the breeding of malaria mosquitoes. Diseases caused by malnutrition are indirectly related to climate, as in food products produced in a particular region, due to the influence of climate on plant growth and soil composition, some nutrients may be lacking.

CLIMATE CHANGE

Rocks, fossil plant remains, relief and glacial deposits contain information about significant fluctuations in average temperatures and precipitation over geological time. Climate change can also be studied by analyzing tree rings of wood, alluvial deposits, ocean and lake bottom sediments, and organic peat deposits. Over the past few million years, the overall climate has been cooling, and now, judging by the continuous reduction of polar ice sheets, we seem to be at the end of the ice age.

Climatic changes for historical period can sometimes be reconstructed based on information about famine, floods, abandoned settlements and migrations of peoples. Continuous series of air temperature measurements are available only for meteorological stations located mainly in the Northern Hemisphere. They span only a little over one century. These data indicate that over the past 100 years, the average temperature on the globe has increased by almost 0.5 ° C. This change did not occur smoothly, but abruptly - sharp warming was replaced by relatively stable stages.

Experts in different fields of knowledge have proposed numerous hypotheses to explain the reasons climate change... Some believe that climatic cycles are determined by periodic fluctuations in solar activity with an interval of approx. 11 years. For annual and seasonal temperatures could be influenced by changes in the shape of the Earth's orbit, which led to a change in the distance between the Sun and the Earth. Currently, the Earth is closest to the Sun in January, but about 10,500 years ago, it was in this position in July. According to another hypothesis, depending on the angle of inclination of the earth's axis, the amount of solar radiation entering the earth changed, which affected the general circulation of the atmosphere. It is also possible that the polar axis of the Earth occupied a different position. If the geographic poles were located at the latitude of the modern equator, then, accordingly, the climatic zones also shifted.

The so-called geographical theories explain long-term climate fluctuations by movements of the earth's crust and changes in the position of continents and oceans. In light of global plate tectonics, continents have moved over geologic time. As a result, their position changed in relation to the oceans, as well as in latitude. In the process of mountain building, mountain systems with a cooler and possibly more humid climate.

Air pollution also contributes to climate change. Large masses of dust and gases that entered the atmosphere during volcanic eruptions occasionally became an obstacle to solar radiation and led to cooling of the earth's surface. Increases in the concentration of some gases in the atmosphere exacerbate the overall warming trend.

Greenhouse effect.

Like the glass roof of a greenhouse, many gases allow most of the sun's heat and light energy to pass to the Earth's surface, but prevent the heat radiated by it from quickly escaping into the surrounding space. The main greenhouse gases are water vapor and carbon dioxide, as well as methane, fluorocarbons and nitrogen oxides. Without greenhouse effect the temperature of the earth's surface would drop so much that the entire planet would be covered with ice. However, exaggerating the greenhouse effect can also be catastrophic.

Since the beginning of the industrial revolution, the amount of greenhouse gases (mainly carbon dioxide) in the atmosphere has increased due to human economic activities and especially the combustion of fossil fuels. Many scientists now believe that the rise in global average temperature since 1850 was mainly due to an increase in atmospheric abundance. carbon dioxide and other greenhouse gases of anthropogenic origin. If modern tendencies The use of fossil fuels will continue into the 21st century, with the global average temperature likely to rise by 2.5–8 ° C by 2075. If fossil fuels are used at a faster rate than currently, such an increase in temperature could occur as early as 2030.

The projected increase in temperature could lead to the melting of polar ice and most mountain glaciers, as a result of which the sea level will rise by 30-120 cm. All this can also affect the changing weather conditions on Earth, with possible consequences such as prolonged droughts in the leading agricultural regions of the world ...

but global warming as a consequence of the greenhouse effect, it can be slowed down if the carbon dioxide emissions from fossil fuels are reduced. Such a reduction would require restrictions on its use all over the world, more efficient energy consumption and expanding the use of alternative energy sources (for example, water, solar, wind, hydrogen, etc.).

Literature:

Poghosyan Kh.P. General circulation of the atmosphere... L., 1952
Blutgen I. Geography of climates, v. 1–2. M., 1972-1973
Vitvitsky G.N. Zonality of the Earth's climate... M., 1980
Yasamanov N.A. Ancient climates of the Earth... L., 1985
Climate fluctuations over the past millennium... L., 1988
Khromov S.P., Petrosyants M.A. Meteorology and climatology... M., 1994