The prevailing westerly wind is moist, but the northwest wind is dry in winter in my country. What’s going on?

1. Equatorial rainy climate

Also known as tropical rainforest climate, it is mainly distributed in the range of 5°-10° south and north latitudes on both sides of the equator, including the Amazon Plain in South America, the Congo Basin in Africa, and the coast of the Gulf of Guinea and most of the Asian Malay Archipelago. It is located at low latitudes and is the source of equatorial air masses. It is also located in the equatorial low-pressure belt, where the trade winds from the northern and southern hemispheres converge and rise, producing a lot of convective rain. It is summer all year round, with the average monthly temperature ranging from 25 to 28°C, and the diurnal range is slightly larger than the annual range. The average annual precipitation is more than 2 000mm, and the monthly precipitation is at least more than 60mm. The zonal soil is tropical rainforest brick red soil.

2． Tropical dry and wet season climate

Also known as savanna climate, it is mainly distributed on the periphery of the equatorial rainy climate zone, generally reaching about 15° south and north latitude, and can also extend to about 25°. Including the Sudanese grasslands in Africa, the Ethiopian plateau, the East African plateau and the northern part of the South African plateau, the Brazilian plateau and Orinoco plain in South America, the Pacific coast of Central America and northern Australia and other regions. The climate is characterized by high temperatures all year round, with obvious dry and wet seasons. In the dry season, it is controlled by the trade winds and prevails tropical continental air masses, which are dry and less rainy; in the rainy season, it is controlled by the equatorial low-pressure belt, and when the equatorial airflow convergence zone moves in, it is humid and rainy. The vegetation soil type is tropical savanna red-brown soil.

3． Tropical arid and semi-arid climates

Mainly distributed in the interior and west on both sides of the Tropic of Cancer, generally between 15° and 30° in south and north latitudes. Typical tropical dry climate areas include the Sahara Desert, Kalahari Desert and Namib Desert in Africa, the Arabian Desert in West Asia, the Thar Desert in South Asia, the western and central deserts of Australia, and the Atacama Desert on the west coast of South America. It is under the control of subtropical high pressure and trade winds all year round. Tropical continental air masses prevail here, and the climate is hot and dry. For example, the world's "hot pole" and "dry pole" both appear in this type of area. Berbera in the northern part of the Somali Peninsula in Africa once had an extreme maximum temperature of 63°C and became the world's "hot pole"; the northern part of Chile in South America The average annual rainfall in the Atacama Desert is close to 0 (the actual measurement in Arica City is 0.7 mm). It never rained for 91 years from 1845 to 1936, and it is called the "dry pole" of the world. As for the tropical semi-arid climate, it is distributed at the outer edge of the arid climate zone, transitioning to the tropical dry and wet season climate zone and the subtropical summer dry climate zone. The vegetation soil type is tropical desert (or desert steppe) desert soil.

4. Tropical monsoon climate

Mainly distributed in Indochina, the Indian Peninsula and the Philippine Islands in Asia. During the season when the sun's altitude angle is high, the equatorial low pressure trough extends north to about 30° north latitude. Coupled with the influence of sea and land thermal factors, a thermal low pressure is formed in the northwest of the South Asian subcontinent. At this time, the southwest monsoon blowing from the Indian Ocean prevails. That is, the summer monsoon forms a rainy season due to high precipitation; in the season with a small solar altitude angle, the equatorial low pressure trough moves southward, coupled with the difference in thermal forces between the sea and land, a weak high pressure develops in the northwest of the subcontinent, and the northeast monsoon prevails at this time , that is, the winter monsoon, which forms a thousand seasons due to low precipitation. In addition, some areas can be subdivided into cool season and hot season. This area has a long summer and no winter climate, with an average annual temperature above 20°C and an average annual precipitation of 1,500-2,000 mm, or even more.

5. Tropical maritime climate

It is mainly distributed on the east coast of the mainland in the trade wind zone of 10°-25° south and north latitudes and on several islands in the tropical ocean, including the east coast of Central America and the West Indies, and the Brazilian Plateau of South America. The narrow strip of land on the east coast, the eastern part of Madagascar in Africa, the coastal strip of Queensland in Australia, and the Hawaiian Islands in the Pacific Ocean. These areas are all located on the windward coast of the trade winds, and tropical marine air masses prevail all year round. In addition, after the trade winds land, they encounter coastal mountains and rise, resulting in a high-temperature and rainy climate with maritime characteristics. The type of vegetation soil formed here is the same as that in equatorial rainy climate conditions, which is tropical rainforest brick red soil.

(2) Terrestrial mid-latitude climate

The mid-latitude zone is the area where tropical air masses and polar air masses intersect. The main circulation systems that affect the climate include polar fronts, prevailing westerly winds, and extratropical cyclones. And anticyclones, subtropical highs and tropical cyclones, etc., have large non-periodic changes in weather and seasonal changes in precipitation. The land mid-latitude climate zone is an area where cold and warm air currents compete with each other. Seasonal and non-periodic changes in temperature and precipitation are very significant. According to thermal conditions, land mid-latitude climate zones are divided into land temperate zones and subtropical zones. Since the global continents are most severely divided by oceans in the mid-latitudes, different climate phenomena and characteristics often appear on the east and west sides of the continent and within the continent, showing dry and wet zonality, which affects the regional division of the natural environment. different.

1. Terrestrial temperate climate

The terrestrial temperate zone is mainly distributed in the area between 35° and 60°N. In the southern hemisphere, only small land extends to the south of 40°N, so the temperate zone is not large. Due to the influence of ocean division, there is an obvious east-west differentiation phenomenon in the temperate zone. Generally, the east coast of the continent has a temperate continental humid climate or temperate monsoon climate, the west coast of the continent has a temperate oceanic climate, and the inland between the two has a temperate continental arid and semi-arid climate.

(1) Temperate continental humid climate

Mainly distributed in the eastern part of the North American continent between 35° and 55°N and the east side of the temperate maritime climate zone of the Eurasian continent. That is, the east side of the temperate maritime climate zone of the Eurasian continent and the area east of 100°W of the North American continent, approximately 40° to 60°N. The temperature and precipitation conditions of this climate are somewhat similar to those of the temperate monsoon climate, but the seasonal changes in wind direction and wind force are not as obvious as those of the temperate monsoon climate. In terms of causes, its cold and dry winters are not caused by the continental monsoon, but because the westerly wind blowing from the ocean has penetrated deep into the land and has undergone continental denaturation, so the temperature is lower and precipitation is less; convection occurs in summer Rain, but the concentration of summer rain is not as significant as in temperate monsoon climate.

(2) Temperate maritime climate

Mainly distributed in the western part of the continent between 40° and 60° north and south latitudes, including the western and southern parts of Scandinavia and Western Europe and most of Central Europe, the Pacific coast west of the Cordillera Mountains of Canada in North America, the area west of the Andes in southern Chile, South America, and places such as Tasmania in Australia and New Zealand. Westerly winds and temperate oceanic air masses prevail here throughout the year, and warm currents pass along the coast, forming a climate characterized by warm winters and cool summers, small annual differences, year-round precipitation, and slightly more rainfall in autumn and winter. In addition, there are more rainy days, more clouds and fog, and less sunshine.

(3) Temperate monsoon climate

Mainly distributed in East Asia around 35°-55°N, including the area north of the Qinling-Huaihe line in eastern my country, the Korean Peninsula, and the northern part of Japan and the southern part of the Russian Far East. The climate causes are similar to the subtropical monsoon climate. In winter, controlled by temperate continental air masses, it is cold and dry, with a large temperature difference between the north and south; in summer, affected by temperate marine air masses or denatured tropical marine air masses, it is warm, hot and rainy, and the temperature difference between the north and south is small. In addition, four distinct seasons and significant non-periodic changes in weather are also the main characteristics of the temperate monsoon climate. Since the climate characteristics of the above temperate climate types are mainly humid (China's North China Plain and Northeast Plains are semi-humid), temperate broad-leaved forest landscapes are more commonly developed (China's North China Plain and Northeast Plains are forest-steppe landscapes). ), but there are some differences. There are more types of broad-leaved trees in East Asia than in Europe, including Quercus mongolica, Quercus liaotungensis, and miscellaneous trees such as Acer, Tilia, and Betula; western Europe often forms pure forests composed of a single tree species, such as beech forests, oak forests, etc.; broadleaf trees in North America The foliage landscape (including south of the Great Lakes, up to the Appalachian Mountains, the Mississippi River Basin, and the Atlantic coastal lowlands) is dominated by American beech and sugar maple. The entire temperate humid broad-leaved forest belt mainly develops colored brown soil and gray brown soil, while the semi-humid forest steppe belt develops cinnamon soil and black soil.

(4) Temperate continental arid and semi-arid climate

Also known as temperate desert and temperate steppe climate, it is mainly distributed in the hinterland of Asia and North America and Patagonia in South America. Places such as the Plateau and the Pampas. Such climate zones in Asia and North America are far away from the sea, deep inland, and surrounded by mountains and plateaus, making it difficult for moist ocean air to reach. Temperate continental air masses prevail all year round, thus forming a temperate continental climate with cold winters, hot summers, dryness and little rain. Arid and semi-arid climates. Generally speaking, the average annual precipitation in arid climates is less than 250 mm, and in semi-arid climates it is 250-500 mm. This type of climate zone in South America is located on the east coast of the continent in the westerly belt. It is the rain shadow area of ??the westerly belt. There are tall Andes Mountains on the west coast. The westerly winds sink after passing through the mountains, resulting in adiabatic warming, dryness and little rain. In addition, there are The cold current passes through, the air is stable, and precipitation is scarce. In the temperate continental arid climate zone, the vegetation is sparse, and the vegetation land type is temperate desert soil; in the temperate continental semi-arid climate zone, the vegetation soil type is temperate steppe chestnut soil.

2． Terrestrial subtropical climate

The terrestrial subtropical climate is mainly distributed in areas between 25° and 40° north and south latitudes. Due to factors such as the subtropical high pressure and the location of sea and land, the east coast of the continent generally has a subtropical humid climate or a subtropical monsoon climate; the west coast of the continent has a subtropical summer dry climate (Mediterranean climate); between the two is a subtropical continental arid and semi-arid climate. .

(1) Subtropical humid climate

Mainly distributed in the 25°-35°N zone in the eastern part of the North American continent and the southeastern edge of the Brazilian Plateau in South America, east of the middle and lower reaches of the Paraná River and the eastern Pampas. In addition, it is also distributed on the southeastern coast of Africa and the southeastern coast of Australia, but the area is smaller. Its main characteristics are that the temperature difference between winter and summer is smaller than that in the subtropical monsoon climate zone, and the distribution of precipitation throughout the year is also more uniform than in the monsoon zone. These areas are similar to the subtropical monsoon climate zone in East Asia in terms of latitude and sea and land location (east coast of the continent). However, because the continental area and adjacent ocean area are small, the thermal difference between sea and land is not as prominent as the latter, so There is no typical monsoon climate.

(2) Subtropical monsoon climate

Distributed in subtropical eastern Asia, mainly including the area south of the Qinling Mountains-Huaihe River in eastern my country, the area north of the tropical monsoon climate zone, southern Japan and the southern tip of the Korean Peninsula . Changes in air pressure configuration caused by differences in sea and land temperatures in winter and summer are the main reasons for the climate in this region.

In winter, the Asian continent is controlled by high pressure, and the northwest wind blowing from the land to the ocean, that is, the winter monsoon, causes less precipitation; in summer, the Asian continent is controlled by low pressure, and the southeast wind blows from the ocean to the land, that is, the summer monsoon, and there is more precipitation. many.

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

(3) Subtropical summer-dry climate

Also known as Mediterranean climate, it is mainly distributed on the west coast of the continent at 30°-40° north and south latitudes. The summer-dry climate in the Mediterranean region has the largest range. , the most obvious features, and also include 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 is normally distributed on the west coast of the subtropical continent, and the climate here is deeply controlled by the seasonal alternation of the subtropical high pressure belt and the westerly belt. In summer, this area is controlled by the subtropical high pressure belt, dominated by downdrafts, and the climate is hot and dry; in winter, controlled by the westerly belt, temperate oceanic air masses prevail, with active cyclones and heavy precipitation. Therefore, hot and dry summers and mild and rainy winters have become the main characteristics of the Mediterranean climate. This type of climate zone mainly forms an evergreen sclerophyllous forest belt, dominated by evergreen shrub forests, and develops brown soil.

(4) Subtropical continental arid and semi-arid climate

Mainly distributed in the interior of the subtropical continent, including the Iranian Plateau and Anatolia Plateau in West Asia, and the interior of the western United States. Continental Plateau and Gran Chaco in South America. The formation of arid climate is due to the fact that it is far inland from the sea or blocked by mountains, making it difficult for moist ocean air to reach. Also, it is located in the subtropics, so it has high temperatures in summer and mild winters. Semi-arid climate is a transition type from arid climate to other climates. The vegetation type here is desert steppe, with xerophytic shrubs and grasses usually growing there, and the soil is semi-desert light brown soil.

(3) Terrestrial high-latitude climate

The terrestrial high-latitude climate zone mainly includes the subarctic zone north of 50'N in the Northern Hemisphere and the terrestrial frigid zone in the Arctic Circle, as well as the Antarctic continent in the Southern Hemisphere. area. The Arctic Ocean and Antarctic ice sheets are the sources of ice ocean air masses and Antarctic air masses respectively. Siberia and Canada are the sources of polar continental air masses in Asia and North America respectively. There is cyclone activity traveling from west to east on the ice-ocean front where the ice-ocean air mass and the polar air mass intersect. The temperature here is low, with the world's coldest pole and the northern hemisphere's coldest pole. The main climate types are subarctic continental climate, polar long-cold climate and polar ice sheet climate. The characteristics of several climate zones are:

1. Subarctic continental climate

Also known as subarctic coniferous forest climate, it is generally distributed between 50°-70°N, and the west coast of the continent is between 60°-70°N, including North Asia. Northern Europe, Alaska in North America and north-central Canada. The climate here is mainly affected by polar ocean air masses and polar continental air masses, and is the source of polar continental air masses. In winter, there are many opportunities for ice-ocean air masses to invade; in the warm season, tropical continental air masses can also penetrate. The climate characteristics are strong continental, long and cold winters, short warm seasons, large annual temperature ranges, low precipitation, concentrated in the warm seasons, weak evaporation, and a cold and humid environment. Verkhoyansk and Oymyakon in northeastern Siberia have an average January temperature of -50°C and an absolute minimum temperature of -73°C, making them the coldest poles in the northern hemisphere. The absolute annual temperature range in Verkhoyansk once reached 101.8°C, making it the place with the largest annual temperature range in the world.

2． Polar long-cold climate

Also known as tundra climate, it is mainly distributed along the Arctic Ocean coasts and islands of the Eurasian continent and the North American continent. The latitude is roughly between 70°-75°N, which is already within the Arctic Circle. , so the phenomenon of extreme day and extreme night is obvious. The climate is characterized by winter all year round, with average monthly temperatures ranging from 0 to 10°C for only 1 to 4 months of the year. Precipitation is scarce, mostly on the ice front, mostly snow, with many clouds and fog, and weak evaporation.

3． Polar ice sheet climate

Mainly distributed in most areas of the Antarctic continent, the Arctic Ocean, and Greenland. It has the highest latitude, and the longest periods of polar day and night can last up to half a year. It has been under the control of polar high pressure for many years and is the source of icy ocean air mass and Antarctic air mass. It is severely cold all year round, with very little precipitation and blizzards common. Due to years of accumulation, huge ice sheets are formed. The Antarctic region is the cold pole, the wind pole and the driest ice and snow continent in the world, while the Arctic region is an ocean of ice caps and floating ice.

(4) Highland climate

Mainly distributed in the Himalayas, Pamir Plateau and Tibetan Plateau in Asia, the Cordillera Mountains in South and North America, the Alps in Europe and Mount Kilimanjaro in Africa and other places. Because climate elements such as temperature and precipitation change vertically as the terrain increases, a vertical climate zone structure is formed. Different mountains or plateaus have different vertical climate zone structures. Even the same mountain or plateau often has different vertical climate zone structures due to differences in its internal slope, height, and location.