Global climate distribution law

Global climatic zones, climatic types and their distribution laws

I. Global climate zones and climate types

Global climate is formed under the comprehensive influence of solar radiation, atmospheric circulation, underlying surface properties and human activities. 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 some similarities; On the other hand, the climate is different because of the different land and sea positions, distance from the sea, ocean current properties, topography and local circulation conditions. 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. But there is no recognized standard in academic circles so far. This is because all climate zones and climate types in nature are gradual, and there is no obvious dividing line. As for the dividing line on the distribution map of climate types, it is artificially divided and is actually a transitional 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 usually considers the influence of precipitation and topography.

In climatology, isotherms are usually used as the boundary to divide climatic zones. Average temperature in the hottest month 10? 0? Taking the isotherm as the dividing line between the cold zone and the temperate zone, the maximum Leng Yue temperature is 18? 0? Isotherm is 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, and the latter is the transition zone of tropical zone. In each climate zone, according to the unbalanced distribution of climate factors such as temperature and precipitation in space and time, various climate types are further divided. 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 zonality law is still clearly visible. From the equator to the polar regions, all kinds of climate types are basically replaced by latitude.

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 heat from the sun, 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, in low-latitude and high-latitude areas, various climate types alternate from north to south according to latitude, mostly distributed in strips, and some even cross the continent from east to west. Such as equatorial rainy climate, tropical dry and wet season climate, low latitude tropical arid and semi-arid climate, polar ice sheet climate, polar long cold climate, high latitude sub-frigid continental climate, etc., are all climate types with obvious zonality.

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 modified it appropriately, and divided the global climate into three latitude zones and plateau climate, and divided it into several climate types in each latitude zone.

(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 affecting 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 the tropical rainforest climate, it is mainly distributed in the range of 5-10 north latitude on both sides of the equator, including the Amazon Plain in South America, the Congo Basin in Africa, the Gulf of Guinea and most parts of the Malay Archipelago in Asia. Located in the low latitude, the source of equatorial air mass, and at the same time in the equatorial low pressure area, the trade winds in the northern and southern hemispheres meet and rise here, and there is more convective rainfall. In summer, the average temperature of each month is 25-28℃, and 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, which can generally reach about north-south latitude15 or 25. 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. In the dry season, controlled by the trade winds, tropical continental air masses prevail, with little rain; 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 the north and south latitudes 15-30. 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, desert in central and western Australia and Atacama Desert on the west coast of South America. Controlled by subtropical high and trade winds all the year round, tropical continental air masses prevail and the climate is dry and hot. 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 type is tropical desert (or desert grassland) desert soil.

4. Tropical monsoon climate

Mainly distributed in Indochina Peninsula, Indian Peninsula and Philippine Islands in Asia. In the season when the solar altitude angle is large, the equatorial trough extends northward to about 30 north latitude, and with the influence of land and sea thermal factors, a thermal depression is formed in the northwest of the South Asian subcontinent. At this time, the southwest monsoon blowing from the Indian Ocean, that is, the summer monsoon, prevailed, and the rainy season was 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, a weak high pressure develops 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 generally 1 500-2 000 mm, or even more.

5. Tropical maritime climate

It is mainly distributed in the east coast of the mainland and several islands in the tropical ocean in the north latitude10-25 trade wind zone, 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 in coastal mountains rose, so a high-temperature and rainy climate with marine characteristics was formed. 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 weather changes aperiodically and the precipitation changes seasonally. 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. According to the heat condition, the mid-latitude climate zone on land can be divided into temperate zone and subtropical zone. Because the global continent is most seriously divided by the ocean in the mid-latitude region, there are often different climatic phenomena and characteristics on the east and west sides of the continent and within the continent, which show as dry and wet zones, thus affecting the regional differentiation of the natural environment.

1. Land temperate climate

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

(1) temperate continental humid climate

It is mainly distributed in the eastern part of North America and the eastern part of Eurasia temperate maritime climate zone between 35 and 55 north latitude, that is, the eastern part of Eurasia temperate maritime climate zone and the area about 40 to 60 N east of North America100 W. 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 by the deep westerly wind blowing from the ocean, which 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 40-60 north latitude, including the western and southern Scandinavia in Europe, most parts of central and western Europe, the Pacific coast west of cordilleras in North America and Canada, the western Andes in southern Chile in South America, and Tasmania and New Zealand in Australia. The westerlies and temperate marine air masses prevail here all the year round, and warm currents pass along the coast, forming a climate characteristic of warm in winter and cool in summer, small annual variation, more precipitation throughout the year and a little more rainfall in autumn and winter. Besides, it's rainy, cloudy and sunny here.

(3) temperate monsoon climate

It is mainly distributed in East Asia near 35-55 N, including the north of Qinling-Huaihe Line in eastern China, the 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; In summer, it is warm, hot and rainy, and the temperature difference between north and south is small due to the influence of temperate marine air mass or denatured tropical marine air mass. 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 (forest and grassland landscape in North China Plain and Northeast China Plain) is generally developed, but there are some differences. There are more kinds of broad-leaved trees in East Asia than in Europe, including Quercus mongolica, Quercus liaotungensis, Acer, Tilia lindleyana, Birch and other miscellaneous trees. In western Europe, pure forests composed of single tree species are often formed, such as beech forests and oak forests. The broad-leaved forest landscape in North America (including the southern Great Lakes, Appalachian Mountains, Mississippi River Basin and Atlantic coastal lowlands) is dominated by American beech and sugar maple. Colored brown soil and gray brown soil are mainly developed in the whole temperate moist broad-leaved forest belt, while cinnamon soil and black soil are mainly developed in semi-humid forest grassland belt.