Climate and weater

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Sun, weather and climate. The influx of sunlight and heat coming to the rotating Earth leads to a daily change in temperature at almost all latitudes, except for the polar caps, where nights and days can last up to six months. Diurnal and annual changes in the illumination of the Earth by the sun's rays lead to complex periodic variability of heating in different regions of the Earth. The result of unequal heating in different parts of the land, ocean and atmosphere is the emergence of powerful jet streams in the oceans, and winds, cyclones and hurricanes in the troposphere. These movements of matter smooth out temperature changes, while they have a strong influence on the weather at every point on Earth and, thereby, form the climate on the entire planet. It can be expected that the thermal regime on Earth, which has been established for thousands of years, should ensure a very accurate recurrence of weather phenomena in each given region. However, in many other places, while maintaining general patterns, noticeable deviations from the average are often observed over many years. All these anomalies, at least partially, can be associated with solar activity.
Against the background of a relatively stable climate, the weather is constantly changing, mainly due to the circulation of the atmosphere. The weather is most stable in tropical countries and most variable in the mid-latitudes and circumpolar regions, in particular, in the North Atlantic and Pacific Oceans, where cyclones often occur and develop. Methods of weather forecasting for the day are based on the construction of daily surface and high-altitude synoptic weather maps, to the analysis of which the general physical laws of atmospheric processes are applied. When forecasting for 3-5 days or more, various statistical techniques are used.
The main types of climate. Climate classification provides an ordered system for characterizing climate types, zoning them, and mapping them. The types of climate prevailing over vast areas are called macroclimates. A macroclimatic area should have more or less homogeneous climatic conditions that distinguish it from other areas, although they are only a generalized characteristic (since there are no two places with identical climates) that are more consistent with reality than the allocation of climatic regions only on the basis of belonging to a certain latitude-geographical zone.
The climate of the ice sheets prevails 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 efficiency of warming up. Most of the incoming solar radiation is reflected by ice. Both in summer and winter, low temperatures prevail in the elevated areas of the Antarctic ice sheet. The climate of the interior of Antarctica is much colder than the climate of the Arctic, since the southern continent is characterized by large size and altitude, and the Arctic Ocean softens the climate, despite the wide distribution of pack ice. In summer, during brief warmths, drifting ice sometimes melts. Precipitation on ice sheets falls in the form of snow or small particles of ice fog. The hinterland receives only 50–125 mm of precipitation annually, but more than 500 mm can fall on the coast. Snowfalls are often accompanied by strong winds that carry significant masses of snow, blowing it off the rocks. Strong runoff winds with blizzards blow from the cold ice sheet, carrying snow to the coasts.
The subpolar climate is manifested in the tundra regions on the northern edges of North America and Eurasia, as well as on the Antarctic Peninsula and adjacent islands. In eastern Canada and Siberia, the southern boundary of this climate belt runs well south of the Arctic Circle due to the strong 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 duration of summer, but in most of the territory the heat received is not enough to completely thaw the soils. Permanently frozen soil, called permafrost, inhibits plant growth and the filtration of meltwater into the ground. Therefore, in summer, flat areas are swampy. On the coast, winter temperatures are slightly higher, and summer temperatures are somewhat lower than in the interior of the continent. In summer, when moist air is above cold water or sea ice, fog often occurs on the Arctic coasts.
The annual amount of 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, the bulk of precipitation can be brought by winter cyclones, but low temperatures and clear weather of the cold season, characteristic of most areas with a subpolar climate, are unfavorable for significant snow accumulation.
The subarctic climate is also known as the "taiga climate" (according to the predominant type of vegetation - coniferous forests). This climate belt covers the temperate latitudes of the Northern Hemisphere – the northern regions of North America and Eurasia, located directly south of the subpolar climate zone. Here there are sharp seasonal climatic differences due to the position of this climatic zone in fairly high latitudes in the internal 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 can sometimes exceed + 32 ° C. In most of the climatic zone under consideration, less than 500 mm of precipitation falls per year, and their amount is maximum on the windward coasts and minimal in the inner part of Siberia. Snow falls very little in winter, snowfalls are associated with rare cyclones. Summers are usually wetter, with rains coming mainly through atmospheric fronts. On the coasts there are often fogs and continuous cloudiness. In winter, in severe frosts, ice fogs hang over the snow cover.
A humid continental climate with short summers is characteristic of the vast strip of temperate latitudes of the Northern Hemisphere. In North America, it stretches from the prairies in south-central Canada to the Atlantic coast, and in Eurasia it covers most of Eastern Europe and parts of 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 areas are determined by the prevailing western transport and the frequent passage of atmospheric fronts. In severe winters, average air temperatures can drop to -18 ° C. Summers are short and cool, frost-free period of less than 150 days. The annual amplitude of temperatures is not as great as in a subarctic climate. In Moscow, the average temperatures in January are -9 ° C, in July - + 18 ° C. In this climatic zone, spring frosts pose a constant threat to agriculture. In the coastal provinces of Canada, in New England and on the island of Hokkaido, winters are warmer than in inland areas, as easterly winds at times bring warmer ocean air.
Annual rainfall ranges from less than 500 mm in the interior of the continents to more than 1,000 mm on the coasts. In most of the area, precipitation falls mainly in the summer, often during thunderstorms. Winter precipitation, mainly in the form of snow, is associated with the passage of fronts in cyclones. Blizzards are often observed in the rear of a cold front.
Humid continental climate with long summers. Air temperatures and the length of the summer season increase southwards in areas of humid continental climate. This type of climate is manifested in the temperate latitudinal zone of North America from the eastern part of the Great Plains to the Atlantic coast, and in southeastern Europe - in the lower reaches of the Danube. Climatic conditions are similar in northeastern China and central Japan. Western transport also prevails here. The average temperature of the warmest month is +22 ° C (but temperatures can exceed +38 ° C), summer nights are warm. Winters are not as cold as in areas of humid continental climate with short summers, but temperatures sometimes drop below 0 ° C. The annual amplitude of temperatures is usually 28 ° C. Most often in a humid continental climate with long summers, 500 to 1100 mm of precipitation falls per year. The greatest amount of precipitation is brought by summer thunderstorms during the growing season. In winter, rain and snowfall are mainly associated with the passage of cyclones and associated fronts.
The maritime climate of temperate latitudes is inherent in the western coasts of the continents, primarily northwestern Europe, the central part of the Pacific coast of North America, southern Chile, southeastern Australia and New Zealand. The course of air temperature is moderated by the prevailing westerly winds blowing from the oceans. Winters are mild with average temperatures of the coldest month above 0 ° C, but when the coasts reach the streams of Arctic air, there are also frosts. Summers are generally quite warm; with invasions of continental air during the day, the temperature can briefly rise to + 38 ° C. This type of climate with a small annual temperature amplitude is the most moderate among the climates of temperate latitudes.
In areas of temperate marine climate, the average annual rainfall ranges from 500 to 2500 mm. The windward slopes of the coastal mountains are the most humid. Cyclones moving from the oceans bring a lot of precipitation to the western continental margins. In winter, as a rule, cloudy weather lasts with light rains and rare short-term snowfalls. Fogs are common on the coasts, especially in summer and autumn.
A humid subtropical climate is characteristic of the eastern coasts of the continents north and south of the tropics. The main areas of distribution are the southeastern United States, some southeastern parts of Europe, northern India and Myanmar, eastern China and southern Japan, northeastern Argentina, Uruguay and southern Brazil, the coast of the province of Natal 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. In the humid subtropics, the average annual precipitation amounts range from 750 to 2000 mm, the distribution of precipitation by season is fairly uniform. In winter, rains and infrequent snowfalls are brought mainly by cyclones. In summer, precipitation falls mainly in the form of thunderstorm showers associated with powerful inflows of warm and humid ocean air, characteristic of the monsoon circulation of East Asia. Hurricanes (or typhoons) occur in late summer and autumn, especially in the Northern Hemisphere.
The subtropical climate with dry summers is typical of the western coasts of the continents north and south of the tropics. In Southern Europe and North Africa, such climatic conditions are characteristic of the coasts of the Mediterranean Sea, which was the reason to call this climate also Mediterranean. The same climate is in southern California, central Chile, extreme southern Africa and parts of southern Australia. All of these areas have hot summers and mild winters. As in the humid subtropics, there are occasional frosts in winter. In the interior in summer, temperatures are significantly higher than on the coasts, and are often the same as in tropical deserts. In general, clear weather prevails. In summer, there are often fogs on the coasts near which ocean currents pass. The maximum precipitation is associated with the passage of cyclones in winter, when the prevailing western air currents shift towards the equator. The influence of anticyclones and downward air flows under the oceans cause the dryness of the summer season. The average annual rainfall in subtropical climates ranges from 380 to 900 mm and reaches 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.
The semi-arid climate of temperate latitudes (synonymous with steppe climate) is characteristic mainly of inland areas remote from the oceans (sources of moisture) and usually located in the rain shadow of high mountains. The main areas with a semi-arid climate are the intermountain 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 actual arid (dry) climate. The average annual rainfall is usually less than 500 mm, but more than 250 mm. Since more precipitation is needed for the development of steppe vegetation in conditions of higher temperatures, the latitude-geographical and altitude position of the terrain determines climatic changes. For a semi-arid climate, there are no general patterns of precipitation distribution throughout the year. For example, in areas bordering the subtropics with dry summers, there is a maximum of precipitation in winter, while in areas adjacent to areas of humid continental climate, rain falls mainly in summer. Temperate cyclones bring most of the winter precipitation, which often falls as snow and can be accompanied by strong winds. Summer thunderstorms often come with hail. The amount of precipitation varies greatly from year to year.
The arid climate of temperate latitudes is characteristic mainly of the Central Asian deserts, and in the western United States - only small areas in the intermountain basins. Temperatures are the same as in areas with a semi-arid climate, but precipitation here is not enough for the existence of a closed natural vegetation cover and the average annual amounts usually do not exceed 250 mm. As in semi-arid climates, the amount of precipitation that determines aridity depends on the thermal regime.
The semi-arid climate of low latitudes is mainly typical of the outskirts of tropical deserts (for example, the Sahara and the deserts of central Australia), where downward air flows in subtropical zones of high pressure exclude precipitation. From the semi-arid climate of temperate latitudes, the climate in question differs in very hot summers and warm winters. 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 the deserts, the maximum precipitation occurs in winter. Precipitation mostly falls in the form of thunderstorms, and in winter the rains are brought by cyclones.
Arid climate of low latitudes. This is a hot dry climate of tropical deserts stretching along the North and South Tropics and being influenced most of the year by subtropical anticyclones. 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 are noticeably higher than + 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 happens that at many meteorological stations for several years in a row precipitation is not recorded at all. Sometimes the average annual rainfall 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, heavy thunderstorm showers, but the water drains quickly, forming flash floods. The driest areas are located along the western coasts of South America and Africa, where cold ocean currents prevent cloud formation and precipitation. On these coasts, there are often fogs formed due to the condensation of moisture in the air over the colder surface of the ocean.
Variable humid tropical climate. Areas with this climate are located in tropical sublatitudinal zones, a few 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 under the influence of the monsoons. Other areas with this climate are the tropics of Central and South America, Africa and Northern Australia. Average summer temperatures are usually around +27 ° C, and winter temperatures are about +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 intratropical convergence zone has a decisive effect on the climate. There are often thunderstorms, sometimes for a long time there is a continuous cloudiness with prolonged rains. Winter is dry, as subtropical anticyclones dominate this season. In some areas, rains do not fall 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 humid tropical forest climate, is common at equatorial latitudes in the Amazon basins in South America and congo in Africa, on the Malay Peninsula and on the islands of Southeast Asia. In the humid tropics, the average temperature of any month is at least + 17 ° C, usually the average monthly temperature is about + 26 ° C. As in the variable humid tropics, due to the high midday standing of the Sun above the horizon and the same length of day throughout the year, seasonal temperature fluctuations are small. Moist air, cloudiness and dense vegetation cover prevent nighttime cooling and maintain maximum daytime temperatures below +37 ° C, lower than in higher latitudes.
The average annual rainfall in the humid tropics ranges from 1500 to 2500 mm, the distribution of seasons is usually quite uniform. Precipitation is mainly associated with the intratropical convergence zone, which is located slightly north of the equator. Seasonal shifts of this zone to the north and south in some areas lead to the formation of two maximums of precipitation throughout the year, separated by drier periods. Every day, thousands of thunderstorms sweep over the humid tropics. In between, the sun shines in full force.
Climates of the highlands. In the highlands, a significant variety of climatic conditions is due to the latitude-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-migrators. The lower limit of eternal snows descends to the poles, reaching sea level in the polar regions. Like it, other boundaries of altitudinal thermal belts decrease as they approach high latitudes. Windward slopes of mountain ranges receive more precipitation. On mountain slopes, open to cold air intrusions, it is possible to lower the temperature. 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 their respective latitudes. The pattern of seasonal changes in temperature and precipitation in the highlands is usually the same as in the adjacent plains.
Climatic zones and local climate features. At the end of the 18th century, a student of M.V. Lomonosov and one of the first Russian academicians, I.I. Lepekhin, outlined a general scheme for the placement of vegetation and fauna on the earth's surface of the world depending on the thermal (climatic) zones. At the beginning of the 19th century, the German naturalist and traveler A. Humboldt established the zonality and altitudinal zonality of vegetation in connection with a change in the amount of heat coming to earth.
Initially, 5 climatic zones stood out on the surface of the Earth: one hot, located on both sides of the equator between the northern and southern tropical circles; two temperate - between the tropical and polar circles and two cold, located around the North and South Poles.
Later, when enough information accumulated about the temperature of the earth's surface in various parts of our planet, the number of climatic zones increased to 7, and the boundaries between them began to be considered not astronomical tropical and polar circles, but lines of equal average temperatures (isotherms). The boundary of the hot belt began to be considered the average annual isotherm of 20 °, the temperate zones - the isotherm of the warmest month in the year + 10 °. From the cold belts, two more belts of eternal frost were isolated, the border between which was drawn along the isotherm of the warmest month of the year 0 °.
If the Earth's axis of rotation were perpendicular to the plane of its orbit (i.e., to the ecliptic), then at each geographic latitude the irradiation by solar radiation would remain always unchanged. In the polar zones, due to the oblique fall of sunlight, the heating of the Earth's surface would be as different as possible from the heating of the equatorial zone by normally falling sunlight. Then the climate on the whole Earth would depend most of all on the geographical latitude (i.e. on the angular distance to the equator). The relatively small tilt of the Earth's axis of rotation leads to a change in the flux of radiation from the Sun at each latitude during the year (i.e. during the Earth's revolution around the Sun). This change is especially strong at the poles (polar zones), in which the duration of the night exceeds a day. In contrast, near the equator, the Sun can culminate at its zenith. Depending on the limits of the possible positions of the Sun above the horizon during the year, it is conditionally accepted to divide the globe into thermal belts: hot (between the latitudes of the tropics from -23.5 ° to + 23.5 °) and two cold, in which the northern and southern latitudes exceed 66.5 °. The rest of the Earth between hot and cold, called temperate zones. Now, using data on temperature and the amount of incoming solar energy (radiation), 13 climatic zones are distinguished, which are usually called geographical: Arctic, Antarctic, subarctic, subantarctic, temperate northern and southern, subtropical northern and southern, tropical northern and southern, subequatorial northern and southern, equatorial. Climatic zones, depending mainly on geographical latitude, are well traced both on land and in the ocean.