- 1 Explain about Cyclones and Measure to be Taken For Prevention of Cyclone
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Explain about Cyclones and Measure to be Taken For Prevention of Cyclone
A cyclone is a huge revolving storm caused by very high speed winds blowing around a central area of very low pressure in the atmosphere. A cyclone is formed over warm sea-water and it is about 10 to 15 kilometres high. A cyclone revolves due to the force exerted by the rotation of earth. The centre of a cyclone is a calm area (having very low air pressure). The centre of cyclone is called the ‘eye’ of the cyclone (see Figure).
The diameter of the eye of cyclone varies from 10 to 30 kilometres. The eye of cyclone is a region free of clouds and it has only light winds. Around the calm and clear eye of cyclone, there is a cloud region of about 150 kilometres in size. In this region, there are very high speed winds (having speeds of 150 km/h to 250 km/h) which are moving in circles around the eye, and thick thunderclouds which produce heavy rain. Away from this region of clouds, the wind speed gradually decreases. A cyclone is known as ‘chakkravaat’ or ‘bavandar’ in Hindi. We will now describe the formation of a cyclone.
How a Cyclone is Formed
A cyclone is formed in the atmosphere over warm sea-water near the equator during the hottest summer months. Factors like temperature, humidity, wind speed, wind direction and rotation of earth, contribute to the development of a cyclone. The formation of a cyclone can be explained as follows :
(i) The sun heats the sea-water too much during summer. Warm and moist air rises up very rapidly from the hot sea surface. This creates area of very low pressure causing cool air to rush in to fill the vacant space.
(ii) As the warm and moist air (containing a lot of water vapour) rises high up in the atmosphere, it gets cooled and the water vapour present in it condenses to form thick clouds (called thunderclouds) releasing a lot of heat in the atmosphere.
(iii) The heat released by the condensation of water vapour in the atmosphere warms the air all around. This warm air rises higher into the atmosphere causing a low pressure. More air rushes up to take the place of warm, rising air. This process is repeated again and again making more and more air to rise up higher and higher in the atmosphere, and also forming more and more thick clouds (or thunderclouds) all around.
(iv) The constant rotation of earth on its axis exerts a force on the rapidly rising columns of air (or winds). The force exerted by the rotation of earth makes the high speed winds revolve in the form of a spiral moving upwards with a great force and create a tunnel of very low pressure inside it (within the thunderclouds) (see Figure).
The swirling winds move faster and faster forming huge circles. This weather condition consistmg of a system of high speed winds revolving around a central area of very low pressure is the cyclone. The area of very low pressure at the centre of the cyclone is its eye (see Figure).
Once a cyclone is formed, it begins to move over the surface of sea. It is sustained by a steady flow of warm and moist air from the warm sea-water. The strongest winds and the heaviest rains occur in the towering thunderclouds about 20 to 30 kilometres from the centre of the cyclone.
The end of a cyclone comes quickly if a cyclone moves over land because it no longer receives heat energy and moisture from warm sea-water. A cyclone is known by different names in different parts of the world. For example, a cyclone is called ‘hurricane’ in the American continent. A cyclone is called ‘typhoon’ in Japan and Philippines.
Destruction Caused by Cyclones
Cyclones are the greatest storms on earth. Cyclones can be very destructive. Cyclones cause widespread- destruction and loss of life in coastal areas in three ways : by producing extremely high speed winds; by lifting the sea-water several metres high ; and by bringing torrential rains. This is discussed below :
(i) The cyclones bring with them extremely high speed winds which cause a lot of destruction. The tremendous force of high speed winds accompanying a cyclone can topple trees, electric poles, telephone poles and vehicles; damage houses; and hurl people through air, etc., causing a great loss of life and property (see Figure).
The strong winds of cyclone produce powerful water waves in the sea and push sea water towards the shore even if the cyclone is hundreds of kilometres away.
(ii) The extremely low pressure in the eye of cyclone lifts the water surface of the sea upwards to a height of 3 to 12 metres. The rising sea water appears like a water-wall moving towards the shore (see Figure).
This water-wall coming from the sea rushes inland with deadly force and causes widespread flooding of low-lying coastal areas. The fast moving flood watersbrought in by a cyclone, destroy roads and railway tracks, wash away vehicles, damage houses, drown people and animals, and damage crops causing a great loss of life and property. The floods caused by cyclone also reduce the fertility of soil in the cyclone hit areas. This is because the fertile top soil is washed away by flood waters brought in by cyclone.
(iii) Cyclones bring with them torrential rains. The continuous heavy rains brought by cyclones may further worsen the flood situation in the area. This increases the problems of the cyclone affected people.
(iv) The floods caused by cyclones pollute drinking water sources. Drinking of polluted water spreads water-borne diseases (like typhoid and dysentery). These diseases kill more people in the cyclone affected areas.
The part of land adjoining the sea (or near the sea) is called coast (or coastal area). The ‘length of coast’ is called ‘coastline’. The whole coastline of India is vulnerable to cyclones. This means that the whole coastline of India is exposed to being hit by cyclones. The east coast of India is more vulnerable to cyclones (or cyclonic storms).
The west coast of India is less vulnerable to cyclones (or cyclonic storms) both in terms of intensity and frequency of cyclones. All the places (cities and villages) in India which lie in the coastal areas are likely to be affected by cylones. For example, the places like Chennai, Mangaluru (Mangalore) and Puri are likely to be affected by cyclones because they are coastal areas (which lie near the sea).
On the other hand, those places which are far away from the sea are unlikely to be affected by cyclones. For example, Delhi, Amritsar and Srinagar are far away from the sea, so they are unlikely to be affected by cyclones (which originate in the sea).
In our country, Orissa was hit by a cyclone on 18th October, 1999. This cyclone had a wind speed of 200 km/h. It destroyed 45,000 houses making 7,00,000 people homeless. Many people were killed. Another cyclone hit Orissa on 29th October the same year. It had a wind speed of 260 km/h.
This cyclone was accompanied by water waves about 9 metres high. Thousands of people lost their lives. Property worth crores of rupees was destroyed. The cyclone affected electricity supply, communication systems, transport and agriculture.
Effective Safety Measures By the Government
The following safety measures should be taken by the Government for the people living in cyclone prone coastal areas to prevent cyclone related disasters :
- Cyclone shelters should be constructed in cyclone prone coastal areas. Cyclone shelters are strong buildings usually built on pillars which can withstand high speed cyclone winds and where cyclone’s flood water cannot enter.
- An efficient cyclone forecast and warning service is essential to prevent cyclone related disasters.
- The cyclone warning should be communicated rapidly to the concerned Government agencies, ports, ships, fishermen and general public living in coastal areas through radio, television, telephones, newspapers and other means.
- Government vehicles (such as buses, trucks, etc.) should be kept ready to evacuate people likely to be affected by cyclone from their homes and move them fast to safer places (such as cyclone shelters).
Action on the Part of People Before a Cyclone Hits Their Area
The following advance planning is required by the people living in the cyclone prone coastal areas if a cyclone warning has been issued in their area :
- Do not ignore the cyclone warnings issued by the Meteorological Department through newspapers, radio or television.
- Make necessary arrangements to shift the essential household goods and domestic animals, etc., to safer places.
- Keep ready the telephone numbers of all the emergency services like police, fire brigade and hospitals.
- Remain in a state of preparedness to evacuate at short notice when asked to do so by the authorities.
Precautions to be Taken After the Cyclone Hits an Area
If a person lives in an area which has just been hit bya cyclone, the following precautions should be observed :
- Do not drink water that could be contaminated by floods (to avoid water-borne diseases). Drink only clean water which has been stored for emergencies.
- Do not touch wet electric switches and fallen electric power lines. Do not use electrical appliances, if wet.
- Do not enter damaged buildings or flood waters. Avoid driving on roads through standing water as floods may have damaged the roads.
- Do not go out just for the sake of fun. Keep listening to local radio for advice. Go out only when it is safe to do so.
- Do not pressurise the rescue teams by making unnecessary demands. Co-operate with the rescue teams and help your neighbours and friends.
Advanced Technology Has Helped in Protection From Cyclones
In the early part of the last century, the available technology was not able to detect the approaching cyclone much in advance. In those days, the people living in coastal areas had less than a day to prepare and evacuate their homes to protect themselves from an oncoming cyclone. The situation today is very different.
Due to advances in technology, we now have satellites and radars. By making use of satellites and radars, a cyclone alert (or cyclone watch) is now issued 48 hours in advance of any expected storm and a cyclone warning is issued 24 hours in advance. This gives sufficient time to people to prepare and evacuate.
The cyclone related message is broadcast over radio every hour or half hour when a cyclone is nearer the coast. Thus, advanced technology has helped in giving us better protection from cyclones.