Cyclone refers to any spinning storm that rotates around a low-pressure centre. Closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce a heavy rain.
Cyclones are characterized by inward spiral winds that rotate about a zone of low air pressure
Warm core cyclones such as tropical cyclones and subtropical cyclones are lie within the synoptic scale Mesocyclones, tornadoes are lie within the smaller mesoscale
Cyclones are also seen on the extra terrestrial planets. Such as Mars. Neptune. Cyclones form due to latent heat driven by significant thunderstorm activity.
TYPES OF CYCLONES
The term ‘cyclone’ actually refers to several different types of storm. There are three types of cyclones.
- Tropical Cyclones
- Polar cyclones
Tropical cyclones are what most people are familiar with because these are cyclones that occur over the tropical ocean regions. Hurricanes and typhoons are actually types of tropical cyclones, but they have different names so that it’s clear where that storm is occurring. Hurricanes are found in the Atlantic and Northeast pacific, typhoons are found in Northwest pacific.
Polar cyclones are cyclones that occur in polar region like Greenland, Siberia and Antarctica. Unlike tropical cyclones, Polar Cyclones are usually stronger in winter months.
Mesocyclone is a cyclone that occurs when part of a thunderstorm cloud starts to spin, which may eventually lead to a tornado. ‘Meso’ means ‘middle’.
Tropical cyclones form only over warm ocean waters near the equator.
To form a cyclone, warm, moist air over the ocean rises upward from near the surface. As this air moves up and away from the ocean surface, it leaves is less air near the surface. So basically as the warm air rises, it causes an area of lower air pressure below.
Air from surrounding areas with higher air pressure pushes in to the low pressure area. Then this new “cool” air becomes warm and moist and rises, too. And the cycle continues…
As the warmed, moist air rises and cools the water in the air forms clouds. The whole system of clouds and wind spins and grows, fed by the ocean’s heat and water evaporating from the ocean surface.
As the storm system rotates faster and faster, an eye forms in the centre. It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.
Difference between Typhoon, Hurricane and Cyclone
The only difference between a hurricane, a cyclone, and a typhoon is the location where the storm occurs. Hurricanes, cyclones, and typhoons are all the same weather phenomenon; we just use different names for these storms in different places.
In the Atlantic and Northeast Pacific, the term “hurricane” is used.
The same type of disturbance in the Northwest Pacific is called a “typhoon” and
“cyclones” occur in the South Pacific and Indian Ocean.
The ingredients for these storms include a pre-existing weather disturbance. warm tropical oceans, moisture, and relatively light winds. If the right conditions persist long enough, they can combine to produce the violent winds..
The main source of energy for cyclones is the warm oceans in the tropical regions.
To initiate a tropical cyclone the sea- surface temperature generally needs to be above 26.5°C however, existing cyclones often persist as they move over cooler water.
The development of a tropical cyclone also relies on favorable broad-scale wind regimes” and can persist for several days with many quite erratic paths. They lose their source of energy when they move over land or colder oceans causing them to dissipate.
Weakening may also occur if the cyclone moves into an unfavorable wind regime which disrupts the structure of the system.
Sometimes a decaying tropical cyclone may interact with a weather system in higher latitudes to cause impacts far from the tropics.
IMPACTS OF CYCLONES
The main impact of cyclone includes heavy rainfall, strong wind, large storm surges at landfall, and tornadoes. The destruction from a cyclone depends mainly on its intensity, its size, and its location after the cyclone has passed, devastation often continues. Some of the impacts of cyclones are
The wind from a category one cyclones cause minimal damage to shrubbery and trees. Category 5 storms are the most forceful, bringing winds of more than 156mph. Wind this fact can rip trees from the ground and flatten buildings. Cyclones that fall in between cause varying degree of distraction, including tearing branches from trees and destroying vegetation
Cyclones can produce flooding in two ways. First, tropical cyclone frequently causes a surge in ocean waters causing sea levels to rise above normal. These surges sometimes called tidal waves, can drown people and animals, and are often the greatest killer in cyclone. Cyclones also can bring torrential rains that lead to flooding.
A cyclone’s high wind can erode the soil, there by damaging existing vegetation and ecosystems. This erosion leaves the area exposed and prone to even more wind erosion. Sand and soil that is blown into other areas can damage the vegetation.
Storm churn happens when a cyclone winds churn up cold water as it moves across the ocean. This churning lowers the water temperature after the storm has passed, squelching the formation of new storms.
DISTRIBUTION OF CYCLONE IN INDIA
Map showing Coastal Areas of India affected by Cyclones
With about 6 percent of the world wide cyclones, the Indian subcontinent is one of the worst cyclone affected areas of the world.
About 8percent of the total land area, particularly along eastern coast and Gujarat coast is vulnerable to cyclones.
Indian Ocean is one of six major cyclone prone regions of the world. On an average, about 5-6percent tropical cyclones are formed in the Bay of Bengal and the Arabian sea every year.
The eastern coast is more prone to cyclones .The total cyclones generated in the Indian ocean, strike the east coast of India.
There are two definite seasons of cyclones in the north Indian ocean. One is from May to June and the other from mid- September to mid-December.
SOME SEVERE CYCLONES RECENTLY HELD IN INDIA
SOME SEVERE CYCLONES RECENTLY HELD IN INDIA
- In West Bengal the cyclone named Komen held in the year 2015, Roanu in 2016 and Mora in 2017
- In Andhra Pradesh the cyclone named Lehar occurs in the year 2013, Hudhud in 2014 and Kyant in 2016
- In Kerala the cyclone named Nada occurs in 2016 and Vardah in 2016
- In Maharashtra the cyclone named ARB 02 occurs in 1994 and phyan in 2009
- In Tamil Nadu the cyclone named Madi in 2013, Roanu in 2016, Kyant in 2016, Nada in 2016 and Vardh in 2016
EFFECTS OF CYCLONES
Cyclones cause heavy rainfall and landslides.
They cause lot of harm to towns and villages, causing severe damage kuccha houses. Coastal businesses like shipyards and oil wells are destroyers and cause many deaths in the ocean and money can also lost if the ship is carrying expensive cargo.
They harm the ecosystem of the surrounding regions.
Civic facilities are disturbed.
Agricultural land is severely affected, especially in terms of water supply and soil erosion.
It cause harm to human, plant and animal life.
Communications systems are badly affected due to cyclones.
Cyclones are the upper ocean heat content, the vertical shear of the environment wind, interaction with other weather systems, impact of dry air and landfall.
Social costs includes, loss of life and livelihood, loss of crops leading to food scarcity.
Education and other services destroyed, increased burden government to rebuild areas affected, and meant for other projects must now be used repair the damage done by the cyclones.
Cyclones can make the sewage pipes block up and stop working and sewage can split everywhere which also causes disease.
SAFETY MEASURES OF CYCLONES.
Check with your local council or your buildings control authority to see if your home has been built to cyclones standards.
Check that the walls, roofs and eaves of your home are secure.
Trim tree tops and branches well clear of your home (get council permission)
Preferably fit shutters, or at least metal screen, to all glass areas.
Clear your property of loose material that could blow about and possibly cause injury or damage during extreme winds.
When a cyclone watch is issued
Re-check your property for any loose material and tie down(or fill with water)all large, relatively light items such as boats and rubbish bins.
Fill vehicles’ fuel tank. Check your emergency kit and fill water containers.
Ensure household members know which the strongest part of the house is and what to do in the event of a cyclone warning or an evacuation.
Tune to your local radio/TV for further information and warnings.
Check that neighbors are aware of the situation and are preparing.
When a cyclone warning is issued
People should evacuate faster as soon as warning is issued
If requested by local authorities, collect children from school or childcare centre and go home.
Park vehicles under solid shelter.
Put wooden or plastic outdoor furniture in your pool or inside with other loose items.
Close shutters or board-up or heavily tape all windows
Benefits of Tropical Cyclones
Although Tropical cyclones are known for destruction they cause, when they strike they also bestow certain benefits to the climatic conditions of that area such as Relieve drought conditions.
Management of Cyclones
There are many structural and non-structural measures for effective disaster management of cyclones. The structural measures include construction of cyclone shelters, construction of cyclone resistant buildings, road links, bridges, canals, drains, saline embankments, surface water tanks, communication and power transmission networks etc.