# Chapter 8 – Winds, Storms and Cyclones

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

When the air moves in a particular direction due to currents, the phenomenon is called winds. Have you ever been to a beach when it is incredibly windy? You must have seen how strong the air current is during the day that your hair and clothes are blown in one particular direction. This happens because a large mass of air is horizontally displaced from the sea towards the beach.

The motion of wind depends on pressure conditions. The wind moves from high pressure to low pressure. Its speed depends on the difference between the pressure of one place from the other.

#### Air Exerts Pressure

Have you ever wondered why a flaccid balloon inflates on blowing air into it? Or why you find it difficult to cycle against the direction of the wind. This is because air exerts pressure. In the first case, it causes the walls of the balloon to stretch, and in the second, it applies pressure against the cycle, making it difficult to ride.

#### High-speed Winds are Accompanied by Reduced Air Pressure

Take a ball of crumpled paper, and keep it just inside the mouth of an empty bottle while holding it parallel to the ground. Now, try to blow inside the bottle forcing the ball of paper to go in. You will find it very difficult to make the ball go inside the bottle, no matter how much force you blow with.

When you blow in the mouth of the bottle, the speed of the air near it is higher. This decreases the pressure at that point. The air pressure is higher inside the bottle than near the mouth. Thus, the air inside the bottle pushes the ball out.

With increased wind speeds, the air pressure reduces, and vice versa.

#### Air Expands on Heating

Take a tube kept in boiling water and stretch a balloon tightly over it. Insert this tube in a beaker that has hot water. Observe what happens to the balloon. Then, place the tube in ice-cold water and observe what happens. You will notice that when the tube was kept in hot water, the balloon was inflated. When it was kept in cold water, the balloon deflated.

This happens because air expands on heating and occupies more space. Thus, warm air is lighter than cold air.

#### Wind Currents are Generated Due to Uneven Heating on the Earth

1. Uneven heating between poles and the equator
You have already learnt that the sun’s heat is maximum at the equator and nearby areas. The air near the equator gets warm and rises up, creating a low-pressure zone. The cold air from the surrounding areas rushes in to take its place, both the north and the south. The polar regions have colder air as compared to 60-degree latitude areas, and as this air rises up, the winds from polar regions rush in to take their place. In this manner, wind circulation takes place from the polar regions to warmer latitudes.
2. Uneven heating of land and water and water
In summer, the land warms up faster near the equator. The temperature on the ground is higher than that on oceans. The air above the land gets heated up and rises, creating a low-pressure area. The winds over the oceans, a high-pressure area, flow towards the land. These are called monsoon winds. These carry water with them and cause rains.

In winter, the direction of the winds is reversed,i.e., from land to the ocean.

#### Storms and Cyclones

Storms

Did you know that thunderstorms are so common that there are about 14 million per year, almost 40,000 per day? Mostly thunderstorms develop in hot and humid regions, like India. When the conditions are hot, and the temperature rises, the air becomes hot and rises upwards. It carries water vapour along with it, which condenses to form clouds on reaching high altitudes. When the water droplets get heavy enough, they fall as rain. Lightning and strong winds accompany rainfall.

Cyclones

The term ‘cyclones‘ refers to weather systems in which the winds or large air masses rotate or spiral violently inwards to an area of low atmospheric pressure. In the Northern hemisphere, the circulation pattern is counterclockwise, while in the Southern hemisphere, it is clockwise.

#### How does a thunderstorm become a cyclone?

During a thunderstorm, when water vapour changes to water at higher altitudes, it releases heat. This heat warms the surrounding air and creates a low-pressure zone. Because of this, cooler winds rush towards the centre of the storm. As the cycle continues, a large low-pressure area is formed, which is accompanied by high-speed winds. This is a cyclone.

#### Conclusion

Moving air is called wind. The circulation of wind over the surface of the earth is regulated by uneven heating. This creates a pressure difference, which causes the movement of air.

#### FAQs

What are wind, storm and cyclone?
When the air moves in a particular direction due to currents, the phenomenon is called winds.
The term ‘cyclone‘ refers to weather systems in which the winds or large air masses rotate or spiral violently inwards to an area of low atmospheric pressure.
A storm is a meteorological phenomenon that is accompanied by high-speed winds and heavy rain.

What is a cyclone?
The term ‘cyclone‘ refers to weather systems in which the winds or large air masses rotate or spiral violently inwards to an area of low atmospheric pressure.

What is the difference between storm and cyclone?
A storm is a meteorological phenomenon that is accompanied by high-speed winds and heavy rain. Whereas a cyclone is a weather system in which the winds or large air masses rotate or spiral violently inwards to an area of low atmospheric pressure.

How does a thunderstorm become a Cyclone?
During a thunderstorm, when water vapour changes to water at higher altitudes, it releases heat. This heat warms the surrounding air and creates a low-pressure zone. Because of this, cooler winds rush towards the centre of the storm. As the cycle continues, a large low-pressure area is formed, which is accompanied by high-speed winds. This is a cyclone.

What are the four types of winds?
Easterly Prevailing Winds, Westerly Prevailing Winds, Polar Easterlies, and Periodic Winds.

### High School Physics

• Alternating Current
• Atoms
• Communication Systems
• Current Electricity
• Dual nature of Radiation and Matter
• Electric Charges and Fields
• Electricity
• Electromagnetic Induction
• Electromagnetic Waves
• Electrons and Photons
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• Gravitation
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• Magnetism and Matter
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• Nuclear Energy
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• Vectors, Scalar Quantities and Elementary Calculus
• Wave Optics
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### High School Chemistry

• Acids, Bases and Salts
• Alcohols, Phenols and Ethers
• Aldehydes, Ketones and Carboxylic Acids
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• Analytical Chemistry
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• Chemical Bonding and Molecular Structures
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• Chemistry in Everyday Life
• Chemistry of p-Block elements
• Chemistry of Transition and Inner Transition
• Classification of Elements
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### High School Biology

• Absorption and Movement of Water in Plants
• Anatomy of Flowering Plants
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• Molecular Basis of Inheritance
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• Neural Control And Coordination
• Nutrition in Human Beings
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• Plant Growth and Development
• Plant Kingdom
• Pollination and Fertilization
• Pollution; Sources and its effects
• Principles of Inheritance and Variation
• Reproduction and Development in Angiosperms
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• The Endocrine System
• The Fundamental Unit Of Life
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• Transport in Plants

### High School Math

• Algebra – Arithmatic Progressions
• Algebra – Complex Numbers and Quadratic Equations
• Algebra – Linear Inequalities
• Algebra – Pair of Linear Equations in Two Variables
• Algebra – Polynomials
• Algebra – Principle of Mathematical Induction
• Binomial Theorem
• Calculus – Applications of Derivatives
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• Geometry – Introduction to Euclid’s Geometry
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• Linear Programming
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• Mensuration – Areas
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• Number Systems
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• Permutations and Combinations
• Probability
• Sequence and Series
• Sets and Functions
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• Trignometry – Height and Distance
• Trignometry – Identities
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### Middle School Science

• Acids, Bases And Salts
• Air and Its Constituents
• Basic Biology
• Body Movements
• Carbon and Its Compounds
• Cell – Structure And Functions
• Changes Around Us
• Chemical Effects Of Electric Current
• Coal And Petroleum
• Combustion And Flame
• Components Of Food
• Conservation Of Plants And Animals
• Crop Production And Management
• Electric Current And Its Effects
• Electricity And Circuits
• Elements and Compounds
• Fibre To Fabric
• Food production and management
• Force And Pressure
• Forests: Our Lifeline
• Friction
• Fun With Magnets
• Garbage In, Garbage Out
• Getting To Know Plants
• Health and Hygiene
• Heat
• Hydrogen
• Life Processes: Nutrition in Animals and Plants
• Materials: Metals And Non-Metals
• Matter and Its States
• Metals and Non-metals
• Micro Organisms: Friend And Foe
• Motion And Measurement Of Distances
• Motion And Time
• Nutrition In Animals
• Nutrition In Plants
• Organization in Living Things
• Our Environment
• Physical And Chemical Changes
• Pollution and conservation
• Pollution Of Air And Water
• Reaching The Age Of Adolescence
• Reproduction In Animals
• Reproduction In Plants
• Respiration In Organisms
• Rocks and Minerals
• Separation Of Substances
• Simple Machines
• Soil
• Some Natural Phenomena
• Sorting Materials Into Groups
• Sound
• Stars And The Solar System
• Structure of Atom
• Synthetic Fibers And Plastics
• The Living Organisms And Their Surroundings
• Transfer of Heat
• Transformation of Substances
• Transportation In Animals And Plants
• Universe
• Waste-water Story
• Water: A Precious Resource
• Weather, Climate And Adaptations Of Animals To Climate
• Winds, Storms And Cyclones

### Middle School Math

• Area and Its Boundary
• Boxes and Sketches
• Data Handling
• Fun With Numbers
• Heavy and Light
• How Many
• Long And Short
• Mapping
• Measurement
• Money
• Multiplication and Factors
• Multiply and Divide
• Numbers
• Parts and Wholes
• Pattern Recognition
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• Play With Patterns
• Rupees And Paise
• Shapes And Angles
• Shapes And Designs
• Shapes and Space
• Similarity
• Smart Charts
• Squares
• Subtraction
• Tables And Shares
• Tenths and Hundredths
• Time