When we blow air into a balloon, the balloon gets inflated and grows bigger. This happens because air pushes the rubber membrane of the balloon from the inside. This simple example shows that air exerts pressure. Various real-life examples showcase how air exerts pressure. During heavy winds, it is tough to pedal a bicycle. Likewise, a boat moving in the direction of the air makes the boat travel faster.

Pressure

Take a crumpled piece of paper and place it just inside the mouth of an empty bottle, parallel to the ground. Now, try blowing inside the bottle to force the paper ball inside. No matter how hard you blow, getting the ball inside the bottle will be impossible.

When you blow into the mouth of the bottle, the speed of air near it increases. It relieves the pressure at that location. The air pressure inside the bottle is higher than near the mouth. As a result, the air inside the bottle pushes out the ball. Therefore, air pressure decreases when wind speed increases, and vice versa.

Air Expands on Heating

When heated, air expands and takes up more space, and as we all know, when anything takes up more space, it becomes lighter in weight. As a result, warm air is always lighter than cold air. Let’s illustrate this with an example.

Light a candle and see whether the flame rises or falls. It always rises because the warm air is lighter than the cold air around it. When heated air rises in a given location, the air pressure falls. 

As a result, cold air fills this space, causing convection in the air. Furthermore, the popular hot air balloon works on this principle.

Irregular heating between the poles and the equator

• You already know that the sun's heat is highest around the equator and neighbouring areas. The air near the equator warms up and rises, resulting in a low-pressure zone. Cold air pours in from the adjacent areas, both north and south, to take its place. Arctic regions have colder air than 60-degree latitude areas, and as this air rises, winds from the polar regions rush in to take its place. Wind circulation from the polar regions to warmer latitudes occurs in this manner.

Irregular heating of land and water

• In the summer, the area near the equator warms up faster. The temperature on the ground is higher than the temperature in the water. The air above the land becomes hot and rises, resulting in a low-pressure zone. The winds over the oceans, which form a high-pressure area, blow towards land. These are known as monsoon winds. These transport water and generate rainstorms.

 

Storms

Did you know that thunderstorms occur at a rate of roughly 14 million per year, or almost 40,000 per day? Thunderstorms are more common in hot, humid places like India. When the weather is hot, as the temperature rises, the air heats up and climbs upwards. When it reaches high elevations, it takes water vapour with it, which condenses to form clouds. When the drops of water become heavy enough, they fall as rain. Lightning and high winds often accompany rainfall.

Cyclones

Cyclones are weather systems in which winds or big air masses violently whirl or spiral inwards to an area of low atmospheric pressure. The circulation pattern in the Northern Hemisphere is counterclockwise, while it is clockwise in the Southern Hemisphere.

How Do Thunderstorms Become a Cyclone?

When water vapour converts to water at higher altitudes during a thunderstorm, it emits heat. This heat warms the surrounding air, resulting in the formation of a low-pressure zone. As a result, cooler winds rush towards the storm's centre. As the cycle progresses, a massive low-pressure area forms, accompanied by high-speed winds. It becomes a cyclone.

What is the difference between a storm and a cyclone?

A storm is a meteorological occurrence characterised by high winds and heavy rain. On the other hand, a cyclone is a meteorological system in which winds or massive air masses forcefully rotate or spiral inwards to an area of low atmospheric pressure.

What prior planning is required to deal with the situation of a cyclone?

• We should not disregard weather warnings issued by the meteorological agency via television, radio, or newspapers.
• We should make the necessary plans to relocate critical home goods, domestic animals, and automobiles, among other things; avoid driving on routes with standing water since floods may have damaged the roadways.
• Phone numbers for all emergency services, such as the police, fire department, and medical centres, should be readily available.
• Always keep a supply of drinking water handy for emergencies.
• Do not come into contact with wet switches or downed electricity lines.
• Cooperate with the rescue team to evacuate people faster.
• Contact friends and family as soon as you are in a safe condition.

Explain why holes are created in hanging banners and hoardings.

Air creates pressure. Banners and hoardings flutter and tear due to this pressure when the wind blows hard. Holes are cut into banners and hoardings to allow wind to get through and keep them from becoming loose and falling.

Provide two ways for determining wind direction at a given location.

Here are two ways to determine the wind direction in any given location

• Notice the direction of dried leaves or other stuff on the road when released in the air.
• Take a piece of paper and hold it in your hand. Allow it to slip from your grasp. It will flow in the same direction as the wind. 

Fill in the blanks with the missing word in the following statements.

(a) Winds are generated due to _________ heating on the earth.

(b) Air moves from a region _________of pressure to a region _________of pressure.

(c) Near the earth’s surface _________ air rises up whereas _________ air comes down.

(d) Wind is ___________air.

Solution 

(a) Winds are generated due to uneven heating on the earth.

(b) Air moves from a region of high air pressure to a region of low air pressure. 

(c) Near the earth’s surface, warm air rises whereas cold air comes down.

(d) Wind is moving air.

Describe two encounters that led you to believe that air exerts pressure.

• When we fill the balloon with air, it becomes tight, and if we try to fill it with more air, the balloon will burst, demonstrating that air exerts pressure.
• Wind causes curtains, doors, and windows to move in the wind's direction, displaying the pressure exerted by air.

How will you assist your neighbours if a hurricane threatens your village/town?

We may assist our neighbours in the event of a cyclone by taking any of the following steps:

• By assisting them in relocating to a more secure location.
• We can help them by moving their animals, necessary household items, and automobiles to a safer location.
• By contacting emergency services such as fire stations, police stations, and medical facilities.

You want to purchase a home. Do you want to buy a house with windows but no ventilators? Explain your answer.

It is not a good idea to buy a house without ventilators. Warm air is lighter than cold air, and hence, escapes through ventilators. Without ventilators, heated air cannot escape, and the house remains warm.

Which of the following locations is unlikely to be impacted by a cyclone?

(i) Chennai (ii) Amritsar (iii) Mangalore (iv) Puri 

Solution:

The answer is (ii) Amritsar because it is distant from the sea, whereas the other three are coastal areas that are more likely to be impacted by a storm.

The wind is an important aspect of moving air. Wind, storms and cyclones occur as a result of differences in pressure and speed of air. It is important to learn about the different aspects of cyclones and storms so that you can be well-prepared during a cyclone situation.

What are the four different sorts of winds?

Easterly Prevailing Winds, Periodic Winds, Polar Easterlies, and Westerly Prevailing Winds are all examples of different types of wind.

What is a cyclone?

The term "cyclone" refers to meteorological patterns in which winds or massive air masses fiercely whirl or spiral inwards to a low-pressure area.

Provide an example of air expanding on heating.

During summers, the air filled into the tires of vehicles is less than the air filled during winters. This is because if an equal amount of air is filled during summers, there is the possibility of tire burst due to the expansion of air due to high temperatures.