Why is it in the news?
1.Cyclone Remal killed 16 people, snapped power links to millions in India and Bangladesh. Strong gales and heavy rain brought by the cyclone Remal lashed the coastline of India and Bangladesh on Monday 27/05/2024, killing 16 people and cutting electricity supply to millions of people in both the countries. The cyclone is blowing at the speed of 135 km/hr and crossed the area around the southern port of Mongla in Bangladesh and adjoining Sagar island in West Bengal, making landfall on Sunday at about 9 pm.
2.Rain flooded roads in the capital Dhaka, flooded the coastal areas in the Sunderbans. The storm has been blowing since last night. Around 1 million people (8 lakh in Bangladesh and around 2 lakh in India) were shifted to shelter places.
3.The storm is expected to move Northeast and gradually weaken further into a deep depression by afternoon, bringing more rain to states in the north east region.
4.At least 15000 houses were damaged in West Bengal. NDRF teams have been deployed in various parts of various districts of WB and rescue operations are underway. Both the central and state governments are taking necessary actions to save the lives of people by sending them into shelter places.
Introduction
1.Tropical cyclones are characterised by destructive winds, storm surges and exceptional levels of rainfall leading to flooding in coastal areas. Winds go up to 200 km/hour. Rainfall takes place 50 cm per day for several consecutive days. Strong winds blow anti-clockwise in the northern hemisphere while in the southern hemisphere, the wind blows in the clockwise direction. The damages on account of tropical cyclones are not only limited to coastal areas but they also spread to the interior areas.
2.India is one of the worst cyclone affected areas of the world. About 8% of the total land area is vulnerable to tropical cyclones. On an average 5-6 tropical cyclones are formed in the Bay of Bengal and the Arabian sea every year. However the eastern coast of India is more prone to tropical cyclones and around 80% of the total tropical cyclones strike the eastern coast of India.
3.There are two important periods for the occurrence of tropical cyclones- May to June and the second period is between September to December.
4.Principle dangers from the cyclones are strong winds, torrential rain and high tidal waves called storm surges.
Kinds of cyclone
1.Three types of cyclones are- one is tropical cyclone, second is severe cyclone and third is super cyclone. When the storm of a cyclone blows at a speed of less than 74 miles/hr it is called a tropical cyclone. When it gets intense and the speed is between 75 to 120 miles/hr then it is called a severe cyclone. When the speed increases for more than 120 miles/hr then it becomes a super cyclone.
4. How do the cyclones originate?
Cyclone is a general term used by meteorologists to describe any rotating, organised cloud that originates over water.
3.Tropical cyclones are violent storms that originate over oceans in tropical areas and move over the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges that are tidal waves causing floods in the coastal areas. They are known as cyclones in the Indian ocean, Hurricanes in the Atlantic and NorthEast Pacific, Typhoons in the South China sea and Western Pacific and Willy Willies in the Western Australia. Cyclones are usually clockwise and hurricanes are counter clockwise.
4.When the atmospheric pressure is low over a large water body that is still and the temperature of the water is more than 27 degree C. They form into a cyclone. The density of air in our atmosphere differs from one place to another place. They are not the same everywhere. When there is low atmospheric pressure on a large water body on the earth surface, they turn into cyclones. This process of thin air circulating, strengthening and developing into cyclonic formation is called cyclogenesis. When the atmospheric pressure is low and the warm air rises to fill the gaps and cold air goes down as they have moisture in it. The warm air becomes more warm and it rises rapidly. Thus, creating more gaps so the surrounding air rushes in to fill the place. This filling air travels at greater speed and from longer distances. When they reach the area, instead of filling the gap they start circulating thus creating a spiral. After that any air travelling to fill the gap has to join the spiral because the air cannot pass through the spiral directly. Usually tropical cyclones range from 100 kms to 2000 kms in diameter. When a large amount of air is rushing to fill the gap, they form huge cyclones and the spiral structures become larger and larger, penetrating the clouds and thus creating thunderstorms. The tropical cyclones can grow up to the height of 10 kms and they last three to seven days depending upon the speed of the storm, how far it is from the land and how big it is. Cyclones usually fade away or die when they cross the land area. There is a misconception that buildings and other interruptions on the land surfaces act as a barrier and stop the cyclone. But that is not true. When the cyclonic storm crosses the land surface, the main source of the cyclone, that is the warm water, is taken away. Cyclones work with moist warm air. So when it crosses a cold water surface or land surface., they die.
Composition of the cyclone
1.Tropical cyclone is composed of an eye which is a region of calm with subsiding air. Around the eye is the eyewall where there is a strong spiralling assent of air to greater height reaching the tropopause. The wind reaches maximum velocity in this region, torrential rain occurs here. Along the eyewall, rain bends radiate and trans of cumulus and cumulonimbus clouds may drift into the outer region. The diameter of the storm over the Bay of Bengal, Arabian in the Indian ocean is between 600-1200 kms. The cyclones create storm surges and they inundate the coastal lowlands.
Difference between tropical cyclone and temperate cyclone
1.Tropical cyclones are formed between 5 degree latitude to 30 degree latitude in the north and south of the latitude. . Cyclones formed around 20 degree latitude on either side of the hemisphere are very severe.
2. Temperate cyclones are formed between 30 degree to 60 degree north and south of the latitude.
3.The temperate (extra tropicals) cyclones have a clear frontal system which is not present in the tropical cyclones.
4.temperate cyclone covers a larger area and can originate over a land and a sea. Whereas the tropical cyclones originate only over the warm seas and on reaching land, they peter out.
5.The temperate cyclones affect a much larger area as compared to tropical cyclones.
6.The wind velocity in a tropical cyclone is much higher and it is more destructive than a temperate cyclone.
7.The temperate cyclones move from west to east but tropical cyclones move from east to west.
Remedial measures
1.Construction of cyclones shelters.
2.Engineered structures instead of thatched houses.
3.Flood management.
4.Evacuation
5.Coastal shelterbelts like by planting strong rooted trees, avoidance of construction of houses near the coastal belts.
6.Cyclone warning system.
7.Cyclone tracking
8.Cyclone detection radars, satellites.
Post disaster rehabilitation measures
1.Evacuation
2.search and rescue operations
3.Providing drinking water
4.Provision of food packets
5.Debris clearance.
6.Reopening of roads.
7.Reestablishment of communication networks in remote areas
8.Medical assistance.
9.Provision for temporary fooding and lodging
10.Disaster assessment
11.Reallocation of budget to rehabilitate the affected people so that they can earn livelihood.
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