Distribution and causes of world climate

I. Global climate zones and climate types

Global climate is formed under the comprehensive influence of solar radiation, atmospheric circulation, underlying surface properties, human activities and ocean currents. According to the differences in the basic characteristics and causes of climate in different parts of the world, the global climate can be divided into several climatic zones. In the same climate zone, on the one hand, the climate has certain similarity; On the other hand, due to the differences in land and sea location, distance from the sea, ocean current properties, topography and local circulation conditions, there are also differences in climate. Accordingly, some climatic zones can be divided into several climatic types. For example, in tropical, subtropical and temperate zones, the three climatic types can generally be divided into east coast, inland and west coast.

Distribution characteristics of climatic zones in the world

The key to the division of climate zone and climate type is to determine the boundary between climate zone and climate type. However, there is no recognized standard in academic circles so far. This is because all climate zones and climate types in nature are gradual and have no obvious boundaries. As for the boundary on the distribution map of climate types, it is artificially divided, and it is actually a transition zone with a certain width. At present, the division of climate zone is usually based on isotherm, and the division of climate types in climate zone is

In climatology, isotherms are usually used as the dividing line for dividing climatic zones. Generally, the average temperature in the hottest month is 10. As the dividing line between the cold zone and the temperate zone, the isotherm has the Leng Yue average temperature of 18. Isotherms are used as the dividing line between temperate zone and tropical zone. Temperate zone spans the widest latitude, and the temperature difference between high and low latitudes is large. It is customary to further divide sub-frigid zone and subtropical zone in temperate zone. The former is the transition zone from temperate zone to cold zone. The latter is a transitional zone in the tropics. In each climate zone, various climate types are further divided according to the uneven distribution of climate factors such as temperature and precipitation in space and time. It can be seen from the world climate distribution map that although the arrangement and combination of climate types on various continents are complex and diverse, the imprint of zonal regularity is still clearly visible, and from the equator to the polar regions, various climate types are basically replaced by latitudes.

The zonality of climate is particularly obvious in the low and high latitudes of the mainland, because the contradiction between cold and warm is relatively stable and constant in these two latitudes. The former receives more sunlight and solar heat, and warm air is the main contradiction, with high temperature all year round and long summer without winter; The latter accepts less sunlight and heat, and cold air is the main contradiction. The temperature is low all year round, and winter is long without summer. Therefore, at low latitudes and high latitudes, various climate types alternate from north to south according to latitude, most of which are distributed in strips, and some even cross continents. For example, low latitude equatorial rainy climate (tropical rain forest climate), tropical dry and wet season climate (tropical grassland climate), tropical arid and semi-arid climate (tropical desert climate), and high latitude polar ice sheet climate.

There are many kinds of climate classification, each with its own advantages and disadvantages. On the basis of Schaller's dynamic climate classification, China climatologists make appropriate modifications and divide the global climate into three latitude zones and plateau climate, and divide each latitude zone into several climate types.

(A) land low latitude climate

The low latitude climate is mainly controlled by equatorial air mass and tropical air mass, with high temperature all year round, and the monthly average minimum temperature is above 15℃. The main circulation systems that affect the climate are intertropical convergence zone, trade winds, equatorial westerly winds, tropical cyclones and subtropical high. The seasonal movement of these systems leads to the seasonal variation of precipitation.

The low latitude climatic zones on land include equatorial zone and tropical zone. It consists of five climate types: equatorial rainy climate, tropical marine climate, tropical monsoon climate, tropical dry and wet season climate and tropical drought and semi-drought. Except for the tropical arid and semi-arid climate, which is distributed inside and outside 30 degrees north and south latitude, all other climate types appear within 25 degrees north and south latitude. Specifically, the land low latitude climate zone includes:

1. Equatorial rainy climate

Also known as tropical rain forest climate, it is mainly distributed in the range of 5.m 10. The northern latitude on both sides of the equator includes the Amazon Plain in South America, the Congo Basin in Africa, the coast of the Gulf of Guinea and most parts of the Malay Archipelago in Asia. It is located at low latitude, the source of equatorial air mass, and at the same time it is located in the equatorial low pressure area, where the trade winds of the northern and southern hemispheres meet and rise, and there is a lot of convective rainfall. It is summer all year round, and the average temperature of each month. The daily range is slightly larger than that of annual range. The average annual precipitation is more than 2000 mm, and the minimum monthly precipitation is more than 60 mm. The zonal soil is tropical rain forest latosol.

2. Tropical dry and wet season climate

Also known as the savanna climate, it is mainly distributed in the periphery of the equatorial rainy climate zone, generally reaching about 15. About 25 degrees north latitude. Including Sudan grassland in Africa, Ethiopian plateau, northern East African plateau and South African plateau, Brazil plateau and Orinoco River plain in South America, Pacific coast in Central America and northern Australia. The climate is characterized by high temperature all year round and obvious dry and wet seasons. The rainy season is controlled by the equatorial low pressure area, and it is wet and rainy when the equatorial airflow convergence zone moves. The vegetation soil type is tropical savanna red brown soil.

3. Tropical arid and semi-arid climate

It is mainly distributed in the inland and west on both sides of the Tropic of Cancer, roughly between north and south latitudes 15.m30. Typical tropical arid climate zones include Sahara Desert in Africa, kalahari desert and namib desert, Arabian Desert in West Asia, thar desert in South Asia, western and central deserts in Australia, Atacama Desert on the west coast of South America, etc. Controlled by subtropical high and trade winds all the year round. Tropical continental air masses prevail and the climate is hot and dry. For example, the "hot pole" and "dry pole" in the world all appear in this type of area. Berbera, in the northern part of the Somali Peninsula in Africa, once recorded an extreme maximum temperature of 63℃ and became the "hot pole" in the world. The average annual rainfall in Atacama Desert in northern Chile of South America is close to 0 (0.7mm measured in Allica), and it never rains during the period from 1845 to 1936, which is called the "dry pole" in the world. As for the tropical semi-arid climate, it is distributed at the outer edge of the arid climate zone, and transits to the tropical dry and wet season climate zone and the subtropical summer arid climate zone respectively. Vegetation soil types.

4. Tropical monsoon climate

Mainly distributed in Indo-China Peninsula, Indian Peninsula and Philippine Islands in Asia. In the season when the sun is high, the equatorial trough extends northward to about 30. North latitude, coupled with the influence of land and sea thermal factors, forms a thermal depression in the northwest of South Asian subcontinent. At this time, the southwest monsoon blowing from the Indian Ocean, that is, the summer monsoon, prevails, and the rainy season is formed due to heavy precipitation. In the season when the solar altitude angle is small, the equatorial trough moves southward, and coupled with the thermal difference between land and sea, there is a weak high pressure in the northwest of the subcontinent. At this time, the northeast monsoon, that is, the winter monsoon, prevailed, and the thousand seasons were distinct due to the lack of precipitation. In addition, some areas can be subdivided into cool season and hot season. The climate in this area is long in summer without winter, the annual average temperature is above 20℃, and the annual average precipitation is 65,438+0,500.

5. Tropical maritime climate

It is mainly distributed on the east coast of the mainland and several islands in the tropical ocean of north and south latitude 10.m25, which are located on the windward coast of the trade winds, including the east coast of Central America and the West Indies, the narrow strip of the east coast of Brazil Plateau in South America, the east of Madagascar Island in Africa, the coast of Queensland, Australia, and the Hawaiian Islands in the Pacific Ocean. These areas are located on the windward coast of the trade winds, and tropical marine air masses prevail all the year round. In addition, after landing, the trade winds meet the coastal mountains and rise, thus forming a high-temperature and rainy climate with marine characteristics. The type of vegetation soil formed here is the same as that of equatorial rainy climate, and it is tropical rain forest latosol.

(2) land mid-latitude climate

The mid-latitude zone is the intersection of tropical air mass and polar air mass. The main circulation systems that affect climate are polar front, prevailing westerly wind, extratropical cyclone and anticyclone, subtropical high and tropical cyclone. The aperiodic change of climate and the seasonal change of precipitation are great. The land mid-latitude climate zone is a region where cold and warm air currents compete with each other, and the seasonal and aperiodic changes of temperature and precipitation are remarkable. The mid-latitude climate zone on land is divided into temperate zone and subtropical zone. Because the global continent is most seriously divided by the ocean in the mid-latitude region, different climatic phenomena and characteristics often appear on the east and west sides of the continent and within the continent, showing dry and wet zones, which affect the regional differentiation of the natural environment.

1. Land temperate climate

The terrestrial temperate zone is mainly distributed in 35. ~60.n, but the temperate zone in the southern hemisphere is not large because only a small piece of land extends to the south of 40.n, and the temperate zone has obvious east-west differentiation due to the division of the ocean. Generally, the east coast of the mainland has a temperate continental humid climate or temperate monsoon climate, the west coast has a temperate maritime climate, and the middle has a temperate continental arid and semi-arid climate.

(1) temperate continental humid climate

It is mainly distributed between 35 in the east of North America. ~55. The eastern part of the Nordic sub-temperate maritime climate zone, that is, the eastern part of the Eurasian temperate maritime climate zone, covers an area of about 40. ~60. Eastern North America. The temperature and precipitation of this climate are somewhat similar to those of temperate monsoon climate, but the seasonal changes of wind direction and wind force are not as obvious as those of temperate monsoon climate. From the cause of formation, its cold and dry winter is not caused by the continental monsoon, but because the west wind blowing from the ocean is deep and has undergone continental degeneration, so the temperature is low and the precipitation is less. There is convective rain in summer, but the concentration of summer rain is not as significant as that of temperate monsoon climate.

(2) temperate maritime climate

It is mainly distributed in the western part of the mainland at latitude 40.m60, including western and southern Scandinavia in Europe, most of western and central Europe, Pacific coast west of cordilleras in North America and Canada, west of Andes in southern Chile in South America, Tasmania in Australia and New Zealand. The westerly and temperate ocean air masses prevail here all the year round, and the warm current passes along the coast, forming the climate characteristics of warm in winter and cool in summer, small annual variation, large annual precipitation and less rainfall in autumn and winter.

(3) temperate monsoon climate

It is mainly distributed in East Asia near 35.m55.N, including the area north of Qinling-Huaihe Line in eastern China, Korean Peninsula, northern Japan and southern Russian Far East. The climate is similar to the subtropical monsoon climate. Winter is controlled by temperate continental air mass, which is cold and dry, with large temperature difference between north and south. Influenced by temperate ocean air mass or denatured tropical ocean air mass, it is warm, hot and rainy in summer, and the temperature difference between north and south is small. In addition, the four distinct seasons and significant weather non-periodic changes are also the main characteristics of temperate monsoon climate. Because the climate characteristics of the above temperate climate types are mainly humid (semi-humid in North China Plain and Northeast China Plain), temperate broad-leaved forest landscape is generally developed (forest grassland landscape in North China Plain and Northeast China Plain), but in Western Europe, pure forests composed of single tree species, such as beech forest and oak forest, are often formed. The broad-leaved forest landscape in North America (including the southern Great Lakes, Appalachian Mountains, Mississippi River Basin and Atlantic lowlands) is dominated by American beech and sugar maple. Color brown soil and gray brown soil are mainly developed in the whole temperate moist broad-leaved forest belt, and cinnamon soil and black soil are developed in the semi-humid forest grassland belt.

(4) temperate continental arid and semi-arid climate

Also known as temperate desert and temperate grassland climate, it is mainly distributed in the hinterland of Asia and North America, Patagonia Plateau and pampas grassland in South America. Climate zones such as Asia and North America are far away from the ocean, deep inland, surrounded by mountains and plateaus, and humid ocean airflow is difficult to reach. Temperate continental air masses prevail all the year round, forming a temperate continental arid and semi-arid climate with hot summer and little rain in winter. Generally speaking, the average annual precipitation in arid climate is less than 250 mm, and the average annual precipitation in semi-arid climate is 250m500 mm. This climate zone in South America is located on the east coast of the continental westerly belt, which is a rain shadow zone, and there are tall Andes mountains on the west coast. The west wind sinks after crossing the mountain, which is warm, dry and rainy. In addition, there is a cold current along the coast, the air is stable and precipitation is scarce. In temperate continental arid climate, vegetation is sparse, and the vegetation land type is temperate desert. The vegetation soil type in temperate continental semi-arid climate zone is temperate grassland chestnut soil.

2. Terrestrial subtropical climate

The land subtropical zone is mainly distributed in the area between 25.m40. Due to the subtropical high and the location of land and sea, the east coast of the mainland generally has a subtropical humid climate or a subtropical monsoon climate. The west coast of the mainland has a subtropical summer dry climate (Mediterranean climate); There is a subtropical continental arid and semi-arid climate between them.

(1) subtropical humid climate

It is mainly distributed in 25.m35.N in the east of North America, the southeast edge of Brazil Plateau in South America, the east of the middle and lower reaches of parana river and the east of pampas grassland. In addition, it is also distributed in the southeast coast of Africa and the southeast coast of Australia, but the area is small. Its main feature is that the temperature difference between winter and summer is smaller than that in subtropical monsoon climate zone, and the precipitation distribution in one year is more uniform than that in monsoon climate zone. From the latitude position and the land and sea position (the east coast of the mainland), both of them are similar to the subtropical monsoon climate zone in East Asia, but because the mainland area is small and the ocean area is adjacent, the thermal difference between land and sea is not as prominent as the latter, so a typical monsoon climate has not formed.

(2) Subtropical monsoon climate

It is distributed in the eastern part of subtropical Asia, mainly including the area south of Qinling-Huaihe River in eastern China, the area north of tropical monsoon climate zone, southern Japan and the southern tip of Korean Peninsula. The change of air pressure configuration caused by different sea-land temperatures in winter and summer is the main reason for the climate formation in this area. In winter, the Asian continent is controlled by the high pressure, and the northwest wind blows from the land to the ocean, that is, the winter wind, with less precipitation. In summer, the Asian continent is controlled by low pressure, and the southeast wind blowing from the ocean to the land is the summer monsoon, with more precipitation.

Evergreen broad-leaved forest is the main vegetation in subtropical humid climate and monsoon climate, and the corresponding soil types are red soil and yellow soil.

(3) subtropical dry summer climate

Also known as the Mediterranean climate, it is mainly distributed on the west coast of the mainland at 30 north latitude. -40. The Mediterranean region has the largest summer drought climate range and the most obvious characteristics. In addition, it also includes the Pacific coast of the southwestern United States, central Chile, the southern tip of Africa and the southern tip of Australia. The planetary wind system on the west coast of subtropical continent is normally distributed, and the climate here is controlled by subtropical high pressure area and westerly wind area in turn. In summer, the sea area is controlled by the subtropical high belt, mainly by the subduction current. Winter is controlled by westerlies, and temperate marine air masses prevail, with active cyclones and more precipitation. Therefore, hot and dry summer and mild and rainy winter are the main characteristics of the Mediterranean climate. This kind of climate zone mainly forms evergreen hardwood forest belt, mainly evergreen shrub and brown soil.

(4) subtropical continental arid and semi-arid climate

It is mainly distributed in the subtropical continent, including the Iranian Plateau and Anatolia Plateau in West Asia, the inland plateau in the western United States and Granchako in South America. The formation of arid climate is because it is far from the sea or blocked by mountains, and it is located in the subtropical zone, so it is hot in summer and mild in winter. Semi-arid climate belongs to the type of transition from arid climate to other climate. The vegetation here belongs to desert grassland, usually xerophytes and grasses, and the soil belongs to.

(3) Land high latitude climate

The land high latitude climate zone mainly includes the sub-frigid zone north of 50 north latitude in the northern hemisphere, the land frigid zone in the Arctic Circle, and the Antarctic continental region in the southern hemisphere. Arctic Ocean and Antarctic ice sheet are the sources of ice air mass and Antarctic air mass respectively, while Siberia and Canada are the sources of polar continental air mass in Asia and North America respectively. On the ice front where the ice air mass meets the polar air mass, there is cyclone activity moving from west to east. The temperature here is low and there is a world.