Thunderstorms And Cyclones
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Thunderstorms And Cyclones
Wind, Storms And Cyclones of Class 7
Thunderstorms develop in hot, humid tropical areas like India very frequently. The rising temperatures produce strong upward rising winds. These winds carry water droplets upwards, where they freeze, and fall down again. The swift movement of the falling water droplets along with the rising air create lightning and sound. It is this event that we call a thunderstorm. The centre of a cyclone is a calm area. It is called the eye of the storm. A large cyclone is a violently rotating mass of air in the atmosphere, 10 to 15 km high. The diameter of the eye varies from 10 to 30 km It is a region free of clouds and has light winds. Around this calm and clear eye (Fig. 8.12), there is a cloud region of about 150 km in size. In this region there are high-speed winds (150–250 km/h) and thick clouds with heavy rain. Away from this region the wind speed gradually decreases. The formation of a cyclone is a very complex process.
How a thunderstorm becomes a cyclone
water requires heat when it changes from liquid to vapour state. the water give back heat when vapour condenses into liquid.Before cloud formation, water takes up heat from the atmosphere to change into vapour. When water vapour changes back to liquid form as raindrops, this heat is released to the atmosphere. The heat released to the atmosphere warms the air around. The air tends to rise and causes a drop in pressure. More air rushes to the centre of the storm. This cycle is repeated. The chain of events ends with the formation of a very low-pressure system with very high-speed winds revolving around it. It is this weather condition that we call a cyclone. Factors like wind speed, wind direction, temperature and humidity contribute to the development of cyclones.
Tornadoes:
In our country they are not very frequent. A tornado is a dark funnel shaped cloud that reaches from the sky to the ground. Most of the tornadoes are weak. A violent tornado can travel at speeds of about 300 km/h. Tornadoes may form within cyclones. The whole coastline of India is vulnerable to cyclones, particularly the east coast. The west coast of India is less vulnerable to cyclonic storms both in terms of intensity and frequency of the cyclones.
NCERT SOLUTION FOR CLASS-7 SCIENCE (Science for grade-7 NCERT solutions)
NCERT Solution for Class 7 Science Chapter 1 - Nutrition in Plants
NCERT Solution for Class 7 Science Chapter 2 - Nutrition in Animals
NCERT Solution for Class 7 Science Chapter 3 - Fibre to Fabric
NCERT Solution for Class 7 Science Chapter 4 - Heat
NCERT Solution for Class 7 Science Chapter 5 - Acids, Bases and Salts
NCERT Solution for Class 7 Science Chapter 6 - Physical and Chemical Changes
NCERT Solution for Class 7 Science Chapter 8 - Winds, Storms and Cyclones
NCERT Solution for Class 7 Science Chapter 9 – Soil
NCERT Solution for Class 7 Science Chapter 10 - Respiration in Organisms
NCERT Solution for Class 7 Science Chapter 11 - Transportation in Animals and Plants
NCERT Solution for Class 7 Science Chapter 12 - Reproduction in Plants
NCERT Solution for Class 7 Science Chapter 13 - Motion and Time
NCERT Solution for Class 7 Science Chapter 14 - Electric Current and Its Effects
NCERT Solution for Class 7 Science Chapter 15 – Light
NCERT Solution for Class 7 Science Chapter 16 - Water: A Precious Resource
NCERT Solution for Class 7 Science Chapter 17 - Forests: Our Lifeline
NCERT Solution for Class 7 Science Chapter 18 - Wastewater Story
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