【 Seasonal movement of wind belt in pressure belt and climate type formed under its influence 】 Wind belt and climate type in pressure belt

Hou, No.5 Middle School in Danyang City, Jiangsu Province

Rule of proposition:

1, assessment content, focusing on basic knowledge. For example, the distribution and movement of pressure belts and wind belts, and the climate types and characteristics formed under their influence.

2. In the form of evaluation, local area map, schematic diagram and specific location map are mostly used to investigate. It focuses on multiple-choice questions and combines with other related knowledge, such as climate types, climate distribution laws, climate characteristics, agricultural activities, etc.

3. In terms of ability, we should pay attention to the basic application of basic knowledge and the ability to transfer knowledge, and require a certain ability to read and analyze drawings.

Secondly, the seasonal movement of pressure belt and wind belt and its influence on climate.

The atmospheric movement is regular, and the global regular atmospheric movement is atmospheric circulation. Atmospheric circulation exchanges heat and water vapor between high and low latitudes and between land and sea, regulates global water and heat distribution, and plays an important role in global heat balance and water balance. Wind belt and pressure belt will be formed in the process of atmospheric movement, which is an important factor of weather change and climate formation in various places. Therefore, wind zone and pressure zone are the focus of geography teaching, and they are important carriers for the cultivation of geographical ability.

1, seasonal movement of wind zone and pressure zone and their main climate types.

The existence of the intersection of the equator and the equator makes the direct point of the sun move back and forth seasonally between the tropic of cancer every year, so the equatorial low pressure area also moves back and forth on the north and south sides of the equator. In the northern hemisphere summer, the equatorial low pressure belt moves between the equator and the north latitude 10; In winter in the northern hemisphere, the equatorial low pressure zone moves between equator and south latitude 10. As the position of equatorial low pressure zone moves, the positions of trade wind zone, subtropical high pressure zone and westerly belt also move.

Home also moves north and south with the seasons. The seasonal movement of pressure belt and wind belt has great influence on the world climate. Then the pressure belt and the wind belt move seasonally in the northern and southern hemispheres every year. In fact, the sun moves north and south with the change of seasons, which causes the periodic movement of pressure belt and wind belt in a year. As far as the northern hemisphere is concerned, it generally moves north in summer and south in winter. Because the pressure belt and the wind belt move regularly from north to south in a year, completely different weather and climate appear in the same area in different seasons.

The climate types formed under the alternate control of seasonal movements of pressure zone and wind zone are mainly tropical grassland climate and subtropical Mediterranean climate.

System decline, less water and withered vegetation; Summer is controlled by equatorial depression, with abundant precipitation and lush vegetation. This is why African herbivores often migrate long distances from north to south with the change of seasons. However, not all savanna climates are caused by the alternating control of equatorial depression and trade winds. For example, the East African Plateau at the equator of Africa, because of its high terrain and vertical changes in water and heat conditions, has not formed a tropical rain forest climate, but a tropical grassland climate; Another example is the savanna climate in western Madagascar, which was formed on the leeward slope of the southeast wind.

The Mediterranean climate is formed under the alternating control of subtropical high and westerlies. Summer is controlled by subtropical high and the weather is hot and dry. Winter is controlled by the westerly belt, and the weather is mild and rainy. Just because of other factors, the Mediterranean climate range is large and small, and the regional morphology is also different. For example, in azania, South Africa, due to the small land area between 30 and 40 south latitude, the Mediterranean climate only appears in the southern corner, with a small area; For another example, the Mediterranean climate along the Pacific coast of America is also very narrow.

Narrow, because the westerlies are blocked by the Cordillera Mountains, which are close to the coast.

Tropical monsoon climate is formed under the interaction of seasonal movement of pressure zone and wind zone and significant difference of thermal properties between land and sea. (See the Climate Comparison Table of East Asia and South Asia for details. )

2. Influence of land and sea distribution on pressure zone.

Due to the influence of the distribution of land and sea, that is, the difference of thermal properties between land and sea, the mainland warmed up quickly in July, forming a low pressure, while the ocean at the same latitude warmed up slowly, and the water temperature was lower than the land temperature, forming a relatively high pressure; In June+10, 5438, the mainland cooled rapidly, forming a high pressure, while the ocean at the same latitude cooled slowly, and the water temperature was higher than the land temperature, forming a relatively low pressure. Because the land area in the northern hemisphere is larger than that in the southern hemisphere, the land and sea are alternately distributed, which has a particularly significant impact on the pressure, making the zonal pressure zone split into high and low pressure centers. In July, the subtropical high was cut off by the Asian low, leaving only the ocean, forming the Hawaiian high and the azores high; On June+10, 5438, the sub-polar low belt was cut off by the Asian high and only remained in the ocean, forming the Aleutian low and the Icelandic low. The ocean area in the southern hemisphere is absolutely dominant, and the zonal pressure zone is more obvious than that in the northern hemisphere, especially in the area south of 30 S, the pressure zone is basically banded.

3. Monsoon circulation and seasonal movement of pressure zone and wind zone.

In Asia, because the high and low pressure centers on the sea and land in summer are powerful and wide in winter, and move north and south with the season, the prevailing winds in large areas of eastern and southern Asia change direction regularly and obviously with the season, that is, monsoon. Monsoon circulation is also an integral part of atmospheric circulation. Due to the imbalance of land and sea distribution and area between the northern and southern hemispheres, the global atmospheric movement is complex. There are pressure zones and wind zones in most areas, while monsoon circulation exists in East and South Asia. The monsoon circulation in East Asia is the most obvious, mainly because it is located between Eurasia, the largest continent in the world, and the Pacific Ocean, the largest ocean in the world, and the thermal properties of land and ocean are very different. In winter, because the equatorial low pressure moves to the south of the equator, South Asia is affected by the Asian high pressure formed by Eurasia in winter, and the northeast monsoon blows, and the winter monsoon is far from the source, so its power is weak; In summer, due to the northward movement of the direct point of the sun, the pressure belt and the wind belt move northward, and the equatorial low merges with the Indian low formed by Eurasia. Under the influence of geostrophic bias, the southeast trade winds in the southern hemisphere turn right across the equator to form a southwest monsoon, which will bring a lot of water vapor and form abundant precipitation. It can be seen that the South Asian monsoon is formed under the influence of the difference of thermal properties between land and sea and the seasonal movement of pressure zone and wind zone.

The southwest monsoon in South Asia is formed because the pressure belt and wind belt move northward seasonally in summer, and the southeast trade wind in the southern hemisphere crosses the equator to the right. Under the influence of the southwest monsoon, the seawater in the North Indian Ocean flows from west to east, forming a clockwise ocean current. Understand this truth, it is not difficult to understand why Zheng He chose to leave in winter and return in summer when he went to the Western Seas in the Ming Dynasty. The reason is that the wind direction and current can be used as the driving force for the ship to move forward.

If the southwest monsoon is strong, it will bring a lot of precipitation; On the contrary, less precipitation will easily lead to drought. Floods and droughts often occur in India, which are caused by the southwest monsoon.

There is also a monsoon in northern Australia-the northwest monsoon. In summer (southern hemisphere season), the northeast trade wind belt in the northern hemisphere moves southward seasonally, crosses the equator, and is biased to the left by geostrophic, forming the northwest monsoon. Obviously, the northwest monsoon here has obvious seasonal changes in winter and the northwest seasonal direction of East Asia, with seawater flowing eastward in summer and westward in winter. However, the flow direction of ocean currents in other sea areas is basically unchanged throughout the year. It is precisely because of the particularity of the North Indian Ocean that the shipping, pollutant diffusion and climate in this sea area show obvious seasonal changes, so it often becomes one of the knowledge points of the candidates in the college entrance examination, and also becomes the focus and difficulty in students' study.

The world ocean currents can be divided into three types according to their causes: wind current, density current and compensation current, and the monsoon current in the North Indian Ocean belongs to wind current according to its causes. In the northern Indian Ocean, due to the narrow sea area, the underdeveloped trade winds in the northeast, the seasonal movement of the positions of the pressure zone and the wind zone, and the tropical monsoon caused by the difference in thermal properties between land and sea are dominant. 10 from June to March-April of the following year, the Asian continent was shrouded by strong high pressure, and the northeast monsoon prevailed in the northern Indian Ocean. The sea water in the Bay of Bengal flows to the southwest, and the south surrounds Sri Lanka Island, forming a northeast monsoon current together with the sea water flowing to the southwest in the Arabian Sea. Then it flows southward along the coast of the Somali Peninsula, forming a Somali warm current, which merges with the northern equatorial warm current, turns around the equator, and flows eastward along the equator to Sumatra Island, forming a fairly obvious equatorial countercurrent. Therefore, the seawater in the North Indian Ocean flows counterclockwise, which is a cyclonic ocean circulation. From May to September, the southwest monsoon prevails, and the sea water movement trend is roughly opposite to that in winter, flowing to the east or northeast. Under the influence of monsoon, the northern branch of the South Equatorial Warm Current crosses the equator, enters the North Indian Ocean, and flows northeast along the Somali coast, forming a Somali cold current. Later, seawater from the Arabian Sea bypassed the west coast of Sri Lanka Island and went southeast, where it merged with the South Equatorial Warm Current to strengthen, and the equatorial countercurrent ceased to exist. So in the North Indian Ocean, seawater flows clockwise, which is an anticyclonic ocean circulation.

World ocean currents can be divided into two types according to the nature of seawater: warm current and cold current. Generally speaking, the monsoon current in the North Indian Ocean belongs to warm current in winter and summer. This is because the sea area is located in the tropics and the water temperature is high all the year round. The reason is the same as that the equatorial current at low latitudes belongs to warm current. However, the current off the coast of Somalia is an exception. Winter is Somali warm current and summer is Somali cold current. Somali current belongs to monsoon current, and its properties change obviously with prevailing winds (northeast monsoon and southwest monsoon). In winter, Somali current flows from northeast to southwest under the influence of northeast monsoon. Because it flows through the equator and the water temperature is high, it is called Somali Warm Current. In summer, Somali current flows from southwest to northeast. Southwest wind (offshore wind) and summer monsoon drive table prevail in the coastal waters of Somalia Peninsula.

Layer seawater flows rapidly to the northeast. After the surface warm water flows away, a relatively cold water mass with low salt content rises from the deep-water basin adjacent to the peninsula to compensate the surface water and become the rising compensation current, resulting in the water temperature along the Somali coast being 2℃ ~ 3℃ lower than that in the nearby waters. In addition, during this period, the direct point of the sun gradually moved northward near the Tropic of Cancer, and the solar radiation in the Arabian Sea and its banks increased, making the surface water temperature in the Arabian Sea as high as 28℃, which was about 5℃ higher than that in the eastern coastal waters of the Somali Peninsula. This is also one of the reasons why the Somali current is cold. The monsoon current in the North Indian Ocean has obvious seasonal variation in the direction of seawater flow in the Straits of Malacca. In winter in the northern hemisphere, the monsoon current in the northern Indian Ocean flows from east to west as a whole, which causes the sea level in the Andaman Sea on the west side of the Straits of Malacca to drop, and the seawater in the South China Sea flows through the Straits of Malacca to compensate. Therefore, the seawater in the Straits of Malacca flows from southeast to northwest as a whole this season. In summer in the northern hemisphere, the monsoon current in the northern Indian Ocean flows from west to east as a whole, which makes the sea level in the Andaman Sea on the west side of the Straits of Malacca rise, and the seawater in the northern Indian Ocean flows to the South China Sea through the Straits of Malacca. So this season, the sea water in the Straits of Malacca flows from northwest to southeast as a whole.

season

summer

season

Third, expand learning ideas.

The movement of pressure belt and wind belt is related to the movement of direct solar point, and the moving range of direct solar point is affected by the intersection angle of yellow and red. Assuming that the declination angle becomes smaller and the moving range of the sun's direct point from north to south will also decrease, what will happen to the climate range of the tropical grassland? If the declination angle is 0, will the Mediterranean climate still exist? ……

The influence of the movement of pressure belt and wind belt on climate is also closely related to the deviation of the earth. The direction of the earth's rotation determines the direction of the geostrophic deflection force, which in turn affects the global atmospheric circulation. If the earth rotates in the opposite direction, will the westerlies still appear on the west coast of the mainland? What kind of climate types will appear in the lower reaches of the Yellow River and the Yangtze River? Is Britain still a temperate maritime climate? How will the climate change in other places? ……

The above assumption is impossible. The reason why this idea is put forward is to inspire students to change their way of thinking, give full play to the ability of reverse thinking and divergent thinking, break through the mindset, boldly expand their imagination and develop their intelligence and ability in an all-round way.

Fourth, online test exercises.

1. Read the schematic diagram of the relationship between some pressure zones, wind zones and airflow on a meridian in a certain month (as shown in the figure). Answer 1 ~ 3.

(1) In Figure (2), the direction and nature of airflow in the pressure belt or the wind belt are () respectively.

A, sinking and drying B, rising and wetting

C, flowing from high latitude to low latitude, drying; d, flowing from low latitude to high latitude, wetting.

(2) In the illustrated month, the following rivers are most likely in the dry season ().

A, parana river B, Congo River C, Mekong River D and Rhine River

(3) There can be no () in the area affected by pressure belt or wind belt between ① and ②.

A, East Africa Plateau B, Brazil Plateau C, Sahara Desert D, Madagascar Island

Reference answer: (1) A (2) C (3) C.

Answer: This topic focuses on the seasonal movement law of pressure zone and wind zone, and takes this as a starting point to examine the knowledge of atmospheric circulation, river recharge and climate type.

1 In the question, ② near the tropic of Capricorn, it is a subtropical high-pressure area with high temperature, dryness and little rain, while item B is the characteristic of low-pressure area, item C is the characteristic of trade winds and polar easterlies, and item D is the characteristic of westerlies, so the correct answer is A.

Question 2: The position of pressure belt and wind belt in the picture is obviously south, and it should be winter in the northern hemisphere. Parana river is located in the subtropical monsoon humid climate zone in the southern hemisphere, which belongs to the wet season, while the Congo River and Rhine River have no obvious dry season. Mekong river is located in the tropical monsoon climate zone in the northern hemisphere, which should be a dry season, so the correct answer is C.

Question 3: The area between ① and ② in the picture is affected by the southeast trade wind. Some or all of the East African Plateau, the Brazilian Plateau and Madagascar are located in the region affected by the southeast wind, while the Sahara Desert is all located in the northern hemisphere, so it is impossible to be affected by the southeast wind. Therefore, the correct answer is C.

When a cargo ship bound for Europe passed through the waters near Colombo, a crew member found his shadow facing south. Some people infer from this fact: ① the ship sails against the current; (2) the ship sailed smoothly; (3) seawater flows counterclockwise; ④ Seawater flows clockwise.

(1), of which the correct one is ()

Answer? ①②B？ ①④C？ ②③D？ ②④

(2) At any time, the geographical phenomenon that can be encountered on ships sailing from Singapore to Hamburg, Germany may be ().

Answer? From the English Channel to Hamburg, you often encounter headwinds.

b？ When we set sail from the Indian Ocean, we sailed against the wind and returned with the wind.

c？ Sailing on the Red Sea is always smooth sailing.

d？ Entering the Atlantic Ocean from the Strait of Gibraltar is sailing against the current.

3. On July 23rd, 2007, a ship carrying cargo departed from St. Petersburg, Russia, and arrived in Kobe, Japan (the route is shown below). Look at the picture and answer the following questions:

(1) When a ship passes through the four sea areas indicated by the numbers in the figure, the deepest draft is the shallowest.

(2) If the ships sail at the same horsepower, why do A and B sail at a higher speed?

Yes, the other place has also slowed down.

(3) When the ship sails to ④, it may or may not encounter a typhoon.

(4) The main climate type at A is.

(5)③ The sea area is located at the junction of plates, and the boundary type is (extinction or growth).

Reference answer:

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