Topic: Air circulation on the Earth

Author: Magdalena Jankun

Target group

2nd grade students of a high school (extended range).

1st grade students of a post‑elementary school (basic range).

Core curriculum

Extended range

3. Earth's spheres - atmosphere. The student:

1) explains the air circulation mechanism in the tropic zone and at higher latitudes, and describes the course of weather processes;

2) explains the origin of permanent, periodic and local winds by giving examples, and indicates their importance for the course of weather and economic activities.

Basic range

III. Atmosphere: climate‑forming factors, distribution of air temperature, atmospheric pressure and precipitation, general atmospheric circulation, synoptic map, climate zones and types of climates.

The student:

2. explains the distribution of air temperature and atmospheric pressure on the Earth;

3. explains the atmospheric circulation mechanism and the distribution of atmospheric precipitation on the Earth.

The general aim of education

You will explain the relationship between air temperature, atmospheric pressure and wind directions.

Criteria of success

• you will explain the terms: atmospheric pressure, low and high;

• you will predict wind directions based on the distribution of high and low pressure centres;

• You will explain the relationship between air temperature, atmospheric pressure and wind directions;

• You will explain the mechanism of passage winds, monsoons, mountain and coastal winds.

Key competences

• communication in the mother tongue;

• communication in a foreign language;

• learning to learn;

• digital competence.

Methods / forms of work

• using ICT tools;

• activity with educational material and multimedia on the epodreczniki.pl platform;

• problematic method: brainstorming;

• activity with the Kahoot application;

• individual activity, activity in pairs, and collective activity.

Teaching aids

• e‑textbook for teaching geography;

• interactive whiteboard;

• multimedia projector;

• tablets/computers;

• physical map of world.

Lesson plan overview

Before classes

1. Students perform interactive exercise number 1 introducing the subject of the lesson (arrange the image from the puzzle). With reference to the image that depicts the model of the global atmospheric air circulation on the days of the equinoxes, the studeny indicated by the teacher explains what the air circulation is. If necessary, the teacher completes the student's statement.

Realization

1. The teacher explains that the air circulation around the Earth, caused by the differentiation of atmospheric pressure at its surface, is called global atmospheric circulation.

2. The teacher explains or asks the students to remember what atmospheric pressure is. It is the force with which the atmospheric air column acts with its weight per unit area. The unit of atmospheric pressure is hectopascal (hPa).

3. The students draw barric systems on the whiteboard (the atmospheric pressure is presented by means of isobars, i.e. lines connecting places with the same pressure values). The teacher emphasizes that the air pressure increases at a high (high‑pressure area) and decreases at a low (low‑pressure area) towards the centre of the system.

4. The teacher refers students to the scheme entitled „The atmospheric air global circulation model on the days of the equinox”. The teacher displays it on the interactive whiteboard. Joint analysis. Indication of the tropic low‑pressure zone, sub‑tropical high‑pressure zone, latitude low‑pressure zones, circumpolar high‑pressure zone. The teacher points out that the difference in pressure between the sub‑tropical high‑pressure zones and the low‑pressure zone in the equatorial zone results in the formation of constant winds called passage winds.

5. The teacher refers the students to source materials, such as a geography textbook, e‑textbook, on‑line resources.

6. The students explain the passage winds, anti‑passage winds, and indicate where they appear on the Earth based on the text. Joint interpretation of the scheme entitled „Circulation of passage winds”.

7. Activity in pairs: using an e‑textbook and other sources, and a geographical atlas, explain what monsoons are, list the causes of their formation and places of occurrence. The teacher displays the scheme entitled „Summer monsoon and winter monsoon” on the main screen which is helpful in completing the task. After the elaboration, the teacher asks eager pairs to discuss the issue. The most interestingly elaborated issues presented on the class forum are graded.

8. The teacher asks the question: What is breeze? The teacher refers the students to their knowledge gained during nature lessons. Discussion. On the interactive whiteboard screen there is displayed the pictures: „Day breeze” and „Night breeze”.

9. Activity in pairs: using an e‑textbook and other sources, explain what a foehn wind is, list the causes of its formation and places of occurrence. The teacher displays the scheme entitled “The mechanism of foehn wind formation” and illustration of its effects on the main screen.

10. Presentation of elaborated material on the class forum by indicated or eager pairs. The teacher assesses the students.

Summary

1. At the end of the lesson, the students do an interactive exercise on the interactive whiteboard: assign the appropriate feature to the wind.

2. The teacher assesses the students' activity during the lesson, appreciating their engagement and commitment.

Homework

Use the Kahoot application to create a quiz that will consist of a minimum of 10 commands. It must refer to the topic of today's lesson. On the next lesson it will be an interesting form to check the students’ knowledge and skills.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Earth’s atmospheric circulation

Atmospheric pressure is the force with which the air column presses on a specific unit of the Earth's surface. By using logic, it can be stated that in the mountains the atmospheric pressure is lower and at the sea level higher. And indeed it is.

The value of atmospheric pressure varies not only depending on the altitude above the sea level. In various places on the globe near the Earth's surface, we find different pressure values. The pressure difference causes the air to move from the higher to the lower. Horizontal or close to the horizontal air movement resulting from the pressure difference is called wind.

The Sun’s uneven illumination of the Earth leads to varied heating of our planet’s surface. Unequal thermal distribution causes local and global movement (circulation) of air. Below, we present Earth’s global air circulation. Please bear in mind that this is only a theoretical description. In a real‑life model, global circulation would be significantly impacted by land, oceans, substantial elevation differences, ocean currents and changing seasons, which are unevenly distributed across the Earth’s surface.

On the equinoxes, the Sun heats the Equator most intensely. Heat causes the air to expand and become lighter. It also causes upward vertical movement of the air (thermal convection) to altitudes of a few or even 11–19 kilometres. At the equator, a low‑pressure zone is created. In this area, a vertical hot air movement is dominant and a surface wind is very weak. That’s why this region is referred to as equatorial calms or doldrums (and is also called the Intertropical Convergence Zone, ITCZ). Air cools down with altitude, causing water vapour to condense and water droplets to fall to the Earth as heavy zenithal (tropical) rain. Moisture‑free and very cold air masses split into two currents and, at an altitude of 12–18 km, move north and south, towards the Tropics. At the Tropics, the cold and condensed air becomes so heavy that it drops to the Earth’s surface. Due to an increase in the atmospheric pressure, the air becomes hot and even drier during its convectional descent. As a result, there isn’t any precipitation near the Tropics. A high‑pressure zone is formed at the Tropics. Some of the air moves back to the Equator, and the rest flows to temperate climate zones. At the poles, cold air drops and generates high atmospheric pressure. Next, it flows down towards the polar circles, and even reaches the temperate climate zone with its ever‑fluctuating pressure patterns.

Differences in atmospheric pressure and altitude occur on Earth very commonly. There are winds everywhere. They can be permanent, periodically variable or local. Permanent winds are those that result from global air circulation. Trade winds - permanent winds in the tropic zone, blowing from the tropics to the equatorial zone of silence with a deviation caused by the rotation of the Earth. Under the influence of the Coriolis force, they blow in the northern hemisphere from the north‑east direction and in the south from the south‑east. Antipasies - winds blowing from the equator to the tropics, but at the height of several or a dozen or so kilometers. Under the influence of the Coriolis force in the northern hemisphere, they blow from the south‑west and south from the north‑west. It should be added that according to the latest descriptions of the general circulation of the atmosphere, the term „antasnatch” is no longer used for the flowing air from the equator towards the higher latitudes.

The western winds are also constant - blowing from the tropics towards the Arctic Circle in both hemispheres and eastern winds blowing from both poles to the Arctic Circle.

Temporary changeable wind is monsoon. Its creation results mainly from the change of seasons and the accompanying differences in the intensity of heating the land and the ocean. In summer, large continents (especially Asia) heat up much stronger than the neighboring oceans (especially the Indian Ocean and Pacific Ocean). The land is much warmer over the land, the air rises and produces a powerful than baric, while above the cooler ocean a high bar is created. The wind called the summer monsoon blows from the ocean and brings precipitation. In winter, the land is colder because it loses heat faster than the oceans, so the dry winter monsoon blows off the coast towards the ocean.

Geographers distinguish dozens of local winds. A typical example is the breeze, that is the wind blowing on the edges of every sea, and even larger lakes. The sea (onshore) breeze blows from the cooler sea (where a higher pressure is generated locally) towards the warmer land (where the atmospheric pressure is lower) during the day. The land (offshore) breeze is formed when the land loses heat at a faster rate than water (atmospheric pressure is higher over land than over water). It blows from the cooled land to the warmer sea at night. The range of this wind is usually a few kilometers.

Another example of local winds is fen. This wind in Poland is called halny. However, in the mountains around the world it has a variety of names. It is formed when there is a difference in atmospheric pressure on two sides of high mountains. The air masses rise and at the same time cool down by 0.6°C for every 100 m. The water vapor condenses and falls in the form of rain or snow. Cold air exceeds the mountains and begins to fall on the opposite side, but because it is already dry, it warms up by 1°C for every 100 m, so it becomes warmer than at the same height on the other side of the mountains. Fen winds are very violent and gusty, and when they occur in winter, they can quickly melt even a thick snow cover. Local winds with different names are also created on the border of extensive plateaus, in wide valleys, near glaciers and ice sheets and on the border of deserts.

• Wind is the level of air movement from high to low.

• The Coriolis force changes the direction of the winds blowing on Earth. In the northern hemisphere the winds from the center of the barium are blowing clockwise, and in the southern hemisphere, contrary to the movement. On the other hand, winds blowing inside the low‑pressure barnacles in the northern hemisphere blow counter‑clockwise and in the southern hemisphere in accordance with it.

• Differences in the Earth's lighting by the Sun cause global air circulation.

• Winds blow everywhere on Earth. They change on a yearly or day scale or have a local character.