WIND STORM AND CYCLONES

                                                     POINT TO REMEMBER
  1. Wind: Moving air is called the wind.
  2. Air exerts pressure. It is this pressure which helps the leaves of trees, banners or  flags to flutter when the wind is blowing.
  3. Increased wind speed is accompanied by a reduced air pressure.
  4. Air moves from the region where the air pressure is high to the region where the air pressure is low.
  5. The greater the difference in pressure, the faster the air moves.
  6. On heating the air expands and becomes lighter.
  7. Warm air rises up whereas comparatively cool air tends to sink towards to the earths surface
  8. Wind current are generated due to uneven heating of the earth e.g.,
  9. Uneven heating between the equator and the poles.
  10. Uneven heating of the land and water.
  11. The winds from oceans carry water and bring rain. These are monsoon winds.
  12. Thunderstorm: In hot and humid area, the rising temperature produces 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. This event is called a thunderstorm,
  13. Cyclone: A very low pressure system with a very high speed winds that revolves around, is called a cyclone.
  14. Cyclones are called hurricane in American continent and in Japan and Philippines-it is called typhoon.
  15. Tornadoes: A tornado is a dark funnel shaped cloud that reaches from the sky to the ground.
  16. Formation of clouds, storms and cyclones is shown in the following flow chart:
 
 
Difference of temperature between two regions
                                                                             
 
Set convection in air
 
 
 
Warm air rises, creating a low pressure area


Cool air converge to the low pressure area
 
 
Warm air rises, cools and the water vapour condenses to form clouds
 
 
The bigger water drop in the cloud to the ground as rain-hail or snow
 
 
Falling water droplets and rising air move vigorously to produce thunderstorm

 
Under certain weather condition storm may develop into cyclones
 

15. Effective safety measures:
Cyclones can be very destructive in its effect. It causes tremendous loss of life and property.            Therefore, we should have effective safety measures.


     i. It has become easier to monitor cyclones with the help of advance technology like satellites and radars.

    ii. Self help is the best help. Therefore, it is better to plan in advance and be ready with defense any approaching cyclone.


16. Anemometer:
The instrument that measures the speed of wind is called as anemometer.


17. Lightning:
When two clouds with unlike charges approach each other, charges start moving with high speed through the air in between when this happens lightning strikes and intense spark of electricity travels in air.
 


 Q.1.  Fill the missing word in the blank spaces in the following statements:

 (a)
Wind is …………………. Air.
 (b) Winds are generated due to …………….. heating on the earth.
 (c) Near the earth’s surface …………… air rises up whereas …………. 
       air comes down.
 (d) Air moves from a region of …………… pressure to a region of  
       ………… pressure.
 
    Ans.   (a)  moving                                          (b) uneven
               (d) warm, comparatively cool           (d) high air, low air  
 
 
 
 
 
 
  Q.2. Suggest two methods to find out wind direction at a given place.

    Ans. 
Two methods to find out wind directions are:
               (i) Using weather cock (Fig. 8.6).
 
             (ii) one simple method used by common people is to hold some dust and release in the air. Dust will fly in the direction of air.
 
Q. 3. State two experiences that made you think that air experts pressure (other than those given in the text).
Ans. Experiment 1: When we fill air in a balloon it inflattens due to pressure exerted by air. Also when it is overfilled with air it bursts due to excess air pressure (Fig. 8.1).


 
                          Fig. 8.1 Air exerts pressure
 

Experiment 2:
When we hang a banner in a place of moving fast air tears due to the pressure exerted by the air.                            
 
Q. 4. You want to buy a house. Would you like to buy a house having windows but no ventilators? Explain your answer.

Ans.
No, we would not like to buy a house having windows but no ventilators. We know that warm air rises upward and cool air comes downward. So to make a stream of cool and fresh air to flow in continuation inside the house through the windows, there must be ventilators in the upper parts of the walls.
 
Q. 5. Explain why holes are made in hanging banners and hoardings.

Ans.
We know that air experts pressure. If there are no holes in the banners and hoardings they will be damaged. To make them safe, holes are made to give the air safe passage.
 
 Q. 6. How will you help your neighbours in case cyclone approaches your village/town?

 Ans.
We will co-operate and help our neighbours, by:
          (i) Making necessary arrangements to shift the essential household goods, domestic animals and vehicles etc. to safer places.
         (ii) Not pressurizing the rescue force by making undue demands.
        (iii) Suggest them:
  • Avoid driving on roads standing water as floods may have damaged the roads.
  • Do not drink standing water that could be contaminated.
  • Do not touch wet switches and fallen powerlines.
  • Do not go out just for the sake of fun.
  
Q. 7. What planning is required in advance to deal with the situation created by a cyclone?

Ans.  
To deal with the situation created by a cyclone we must do the following planning in advance. On the  Part of the government
              (i) Rapid communication of warnings to the government agencies, the ports, fishermen, ships and to the general public must be ensured.
             (ii) There must be the construction of cyclone shelters in cyclone prone areas and administrative arrangements for moving people fast to safer places.
         On the part of the public
              (i) Keep ready the phone numbers of all emergency services like police, fire brigade and medical centres.
            (ii) Make necessary arrangements to shift the essential household goods, domestic animals and vehicles, etc. to safer places.  
 
Q. 8. Which one of the following place is unlikely to be affected by a cyclone:
             (i) Chennai                                (ii) Mangaluru (Mangalore)
           (iii) Amritsar                              (iv) Puri
Ans.    (iii) Amritsar.
 
Q. 9. Which of the statements given below is correct?
         (i) In winter the winds flow from thee land to the ocean.
         (ii) In summer the winds flow from the land towards the ocean.
        (iii) A cyclone is formed by a very high-pressure system with very high-speed.
        (iv) The coastline of India is not vulnerable to cyclones.
Ans.  (i) In winter the winds flow from the land to the ocean.
 
                     
ADDITIONAL IMPORTANT QUESTIONS
                
                  
                      
 Q. 1. What is wind?
 Ans.  A large scale movement of air is called the wind?
 
 Q. 2.  Why the leaves of trees, banners or flags flutter when the wind blow?
 Ans.  Due to the pressure exerted by the air.
     
Q. 3. How the difference in the pressure at two places is determines the movement of air?
  Ans. Air moves from the high pressure region to low pressure region.
         
Q. 4. What is the effect of heat on air?
Ans.  On heating, the air expands and becomes lighter.
 
Q. 5. What is the main cause of wind movements on the earth?
Ans. Wind currents are generated due to the uneven heating on the earth.
 
Q. 6. What is a monsoon?
Ans. These are the winds from the oceans that carry water and bring rain.
 
Q. 7. In which type of climate does the thunderstorms develop very frequently?
 Ans. Thunderstorms develop in hot and humid tropical areas like, India where it is frequent.
 
Q. 8. What is a cyclone?
Ans. It is a very low pressure system with very high speed winds revolving around it.
 
Q. 9. What are the other names of cyclones?
Ans. Cyclones are called:
         (i) Hurricane in the American continent.
 and (ii) Typhoon in Phillippines and Japan.
 
 Q. 10. What is a tornado?
 Ans. A tornado is a dark funnel shaped cloud that reaches from the sky to the ground.
 
Q. 11. Name two modern technologies which help in making a forecast of a cyclone.
Ans. Two such devices are: (i) Satellites and (ii) Radars.
 
Q. 12. Explain why hot air goes up?
Ans. On heating the air expands and occupies more space. When the same volume of air occupies more space, it becomes lighter. The hot air therefore, becomes lighter than the cold air. That is the reason why hot air goes up.
 
Q. 13. Give an experiment to show that increased wind speed is accompanied by a reduced air pressure.
Ans.

Fig. 8.2. Blowing into the bottle
                Crumple a small piece of paper into a ball, of such a size, that remains smaller than the mouth of an empty bottle. Hold the empty bottle from its side and place the paper ball just inside its mouth. Now try to blow on the ball to force it into the bottle.
               When we blow into the mouth of the bottle, the air near the mouth has higher speed. This decreases the pressure there. The air pressure inside the bottle is higher than near the mouth. The air inside the bottle pushes the ball out.
 
Q. 14. Explain why if we blow air between the balloons of nearly equal size hanging 8-10 cm apart, they come towards each other.
 

 
 
Fig.8.3. Blowing between the balloons
Ans. We know that increased wind speed is accompanied by a reduced air pressure. When we blow air between the two balloons the pressure between them is reduced. The pressure outside the balloons would then push them towards each other.
 
Q. 15. Discuss in brief that how uneven heating between the equator and the poles generates wind current.
Ans. We know that the region close to the equator gets maximum heat from the sun. This makes the air warm which rises up into the air. The air from that regions to 0-30 degrees latitude belt on either side of the equator, moves in. These winds blow from the north and the south towards the equators.
         At the poles, the air is colder than at latitudes about 60 degree. The warm air at these latitudes rises up and the cold wind from the poles rushes in. In this way wind circulation is set up from the poles to the warmer latitudes. (Fig. 8.4).
 
 
 
 

Fig. 8.4. The wind flow pattern because of uneven heating on the earth
 
Q. 16. What is a thunderstorm? How does it develop?
Ans. Thunderstorms develop in hot and humid tropical areas. The temperature when rises, it produces strong upward rising winds. These winds carry water droplets upwards where they freeze and fall down again. The swift movements of the falling water droplets along with the rising air create lightning and sound. It is this event to which we call a thunderstorm.
 
Q. 17. What is a tornado? Give its structure.
Ans.  A tornado is a dark funnel shaped cloud that reaches from the sky to the ground. The diameter of a tornado can be as small as a metre and as large as a kilometer or even wider. The funnel sucks dust debris or everything that comes near its base (due to low pressure) and throws them out upto the top.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Fig. 8.5. The wind flow pattern because of uneven heating on the earth
Q. 18. What precautions would you take if you are facing a storm with lightning?
Ans.  If a storm is accompanied by lightning. We should must take the following precautions:
  • Do not take shelter under an isolated tree. If you are in a forest take shelter under a small tree. Do not lie on the ground.
  • Do not take shelter under an umbrella with a metallic end.
  • Do not sit near a window, open garages, storage sheds and metal sheds are not the safe place to take shelter.
  • A car or a bus is a safe place to take shelter.
  • If you are in water, get out of it and go inside a building.
 
Q. 19. What is an anemometer? Draw its structure.
Ans. The instrument that measures wind speed is called an anemometer. Since wind speed plays an important role in the formulation of storms but the anemometer becomes useful to predict the cyclones or storms in cyclone prone areas.

 
Fig. 8.6. An anemometer for measuring the speed of wind
 
Q.20. Explain the formation of monsoon.
Ans. In summer, the land warms up faster near the equator, and most of the time the temperature of the land is higher than that of water in the oceans. The air over the land gets heated and rises. This causes the winds to flow the oceans towards the land. These are monsoon winds, in winter, the direction of the wind flow gets reversed; it flows from lands to oceans.
                   The winds from the oceans carry water and results in bringing rain. It is also a part of the water cycle.
 
Q. 21. How a cyclone is formed?
Ans. Water heat up because of atmospheric heat and turns into vapour. When this water vapour gets condensed, it changes back into liquid as raindrops.
         The heat released from 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.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Fig. 8.7. Image taken by a satellite of a cyclone approaching the coast of Orissa
 
Q. 22. Write a note on the disaster management in respect to cyclones.
Ans. Cyclones can be very destructive, when the low pressure in the eye lifts water from the surface layer in the centre. The rising water may be as high as 3-2 meters. It appears. Like a water-walls moving towards the shore. As a result, the seawater enters the low-lying coastal areas, causing severe loss of life and property. It also reduces the fertility of the soil.
          The disaster management of a cyclone involves:
    (A) Effective Safety Measures:
  1. A cyclone forecast and warning service.
  2. Rapid communication of warning to the government agencies, the ports,
      fishermen, ships and to the general public.
  1. Construction of cyclone shelters in the cyclone prone areas and administrative
arrangements for moving people fast to safer places.
   (B) Action on the part of the People:
  1. We should not ignore the warning issued by the meteorological department through media like TV, radio or newspapers.
  2. We should
  3. Make necessary arrangements to shift the essential household goods, domestic animals and vehicle etc. to safer places;
  4. Avoid driving on roads through standing water, as floods may have damaged the roads; and
  5. Keep ready the phone numbers of all emergency services like police, fire brigade and medical centre.
 (C) Some other precautions if you are staying in a cyclone prone area:
  • Do not drink water that could be contaminated. Always store drinking water for emergencies.
  • Do not touch wet electric switches and fallen powerlines.
  • Do not pressurise the rescue force by making undue demands.
  • Co-operate and help your neighbours and friends.
 
Q.23. Describe the structure of a cyclone using a diagram.
Ans: 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, i.e., around 10 to 15 km high. The diameter of the eye varies from 10 to 30 km (fig. 8.8). It is a cloud free region with a mixture of the light wind in it. Around this clam and clear eye (fig. 8.8), there is 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. A diagram is shown in fig.8.9.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Fig. 8.8. The image of the ‘eye’ of a cyclone
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Fig. 8.9. Formation of a cyclone
 
OBJECTIVE TYPE QUSTIONS
Q.1. Match the items given under Column I with those given in Column II.
Column IColumn II
  1. Winds
  2. Monsoon
 
  1. Thunderstorm
  2. Cyclone
  3. Tornado
  4. Anemometer
  1. dark funnel shaped cloud
  2. Very low pressure system with very high speed winds revolving around it.
  3. Measures the speed of wind
  4. Develop in India very frequently
  5. Moving air
  6. Winds carrying water
 
Q.2. Fill in the blank space in the following statements:
  1. Moving ………….. is called a winds.
  2. Air exerts ……………
  3. Increased wind speed is accompanied by …………… air pressure.
  4. The warm air is ………….. than cold air.
  5. Winds currents are generated due to ………….. heating on the earth.
  6.   Very …………… pressure system with very ………….. speed winds revolving around it is called a cyclone.
  7. A dark  funnel shaped …………. that reaches from the sky to the ground is called a tornado.
  8. ………….. and ………….. have made possible to issue a cyclone alert, i.e., 24 hours in advance.
 
Q.3. Choose the true and false statements from the following:
  1. Air around us exerts pressure.
  2. Air contracts on heating and expand on cooling.
  3. As cool air rises air pressure at that place is reduced and the warmer air moves to that place.
  4. Winds carrying water vapours bring rains.
  5. High speed winds and air pressure differences can cause cyclones.
  6. Cyclones are beneficial to the people living in coastal areas.
  7. Tornadoes are very frequent in our country.
  8. It has become easier to monitor cyclones with the help of advance technology like satellites and radars.
 
Q. 4. Choose the correct option in the following:
  1. In which year Orissa was hit by a cyclone?
  (a) 1999                                        (b) 2000
  (c) 2001                                        (d) 2004
 
  ii.   Leaves of trees, banner of flags flutter when wind is blowing. Why?
           (a) Air occupies space                  (b) Air is a mixture of gases
           (c) Air exerts pressure                  (d) Air is colorless  
        iii.    When we blow over a paper strip it goes upward as shown in the figure given      
                 below. Why?
                   
 
 
 
Fig. 8.10. Blowing over a strip of paper
 
 
 
 
     
                  (a) Blowing over the paper reduces the air pressure above the strip
                  (b) Blowing over the paper increases the air pressure above the strip
                  (c)  None of these is a correct reason
                  (d) The strip will not go upward at all.         
     
         iv    When we blow between the two balloons as shown in the figure what will happen?
                  (a) Balloons will move towards each other
                  (b) Balloons will move away from each other
                  (c) Balloons will remain on their original position
                  (d) Cannot say
         
          v      Air moves from
                  (a) The region of high pressure to low pressure
                  (b) The region of low pressure to high pressure
                  (c) Does not depend upon the pressure
                  (d)  Air does not move
        vi.     The winds from oceans carry water and bring rain. These winds are called
                  (a) typhoon                                                   b) monsoon
                  (c) cyclone                                                   d) none of these
 
       vii.    What is a cyclone?
                 (a) winds from the oceans carrying water
                 (b) Very low pressure system with very high speed winds revolving around it.
                 (c) Dark funnel shaped cloud that reaches from the sky to the ground.
                (d) None of the above.
 
  1. Pick the odd one out?
(a) Cyclone                                                   b) Hurricane
(c) Monsoon                                                 d) Typhoon
 
  1. A cyclone warning can be issued
    (a) 48 hours in advance                                b) 12 hours in advance
    (c) 6 hours in advance                                  d) 24 hours in advance
  
  1. Lighting emerge due to the collision of
    (a) atoms                                                       b) molecules
    (c) charges                                                    d) clouds
 
  1. Most of the atmospheric air is present in
    (a) Troposphere                                            b) Stratosphere
   (c) Mesosphere                                              d) Therosphere
 
  1. Name the standard instrument for measuring atmospheric pressure.
    (a) Voltmeter                                                b) Thermometer
    (c) Mercury barometer                                 d) Multimeter
 
  1. Unit of pressure is
    (a) Newton                                                   b) m/s²
    (c) Pascal                                                     d) BM
 
  1. Tropical cyclones that originate in the U.S.A.
    (a) Tornado                                                  b) Cyclones
    (c) Typhoons                                               d) Hurricanes
 
  1. The movement of air is know as
    (a) Variable wind                                        b) Cyclones
    (c) Wind                                                      d) Tornadoes
 
 
ANSWER TO OBJECTIVE TYPE QUESTIONS
Q.1. Match the item in Column I with Column II:
 
Column IColumn II
  1. Winds
  2. Monsoon
  3. Thunderstorm
  4. Cyclone
 
  1. Tornado
  2. Anemometer
e.    moving air
f.    winds carrying water
d.   develops in India very frequently
b.   Very low pressure system with very    high speed winds revolving around it
a.  dark funnel shaped cloud
c.  measures the speed of wind

 
Q.2. Fill in the blanks:
        i. air                                      ii. pressure                         iii. reduced
      iv. lighter                               v. uneven                            vi. low, high
     vii. cloud                             viii. satellites, radars.                   
 
Q.3. True/False
       i. True                     ii. False                   iii. False               iv. True
      v. True                    vi. False                  vii. False                x. True
 
Q.4. Choose the correct option:
      i.  (a)                   ii. (c)               iii. (a)               iv. (a)             v. (a)
    vi.  (b)                 vii. (b)             viii. (c)              ix. (a)             x. (c)
    xi.  (a)                 xii. (c)              xiii. (c)             xiv. (a)          xv.