Class 7th Science Chapter 8 Winds, Storms and Cyclones is a very interesting topic for students. It has some of the important concepts related to winds and storms, which are useful in real life. The syllabus for this topic is prepared by expert teachers by updating the current CBSE syllabus. Some of the topics you will learn are:
Air Exerts Pressure
Uneven Heating of the Earth Generates Wind Currents
Storms and Cyclones
Air Expands on Heating
How Do Thunderstorms Become a Cyclone?
The wind is a phenomenon in which air moves in a particular direction due to currents. Cyclones frequently disrupt agriculture, transportation, communication, and power supply in a given area.
Have you ever thought about what cyclones are? How do they come to be? What exactly is a storm? Where does it come from?
In this chapter, you will find answers to all of your queries about wind, storms, and cyclones.
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.
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.
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 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?
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
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.
(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.
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:
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
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.