Tropical cyclones are violent storms that originate over oceans in tropical areas and move over to the coastal areas bringing about large scale destruction caused by violent winds, very heavy rainfall and storm surges.
Tropical Cyclones are one of the most devastating natural calamities in the world.
Cyclones are a type of low-pressure environment with rapid inward air circulation. The word Cyclone comes from the Greek word Cyclos, which means snake coils.
Northern Hemisphere, air flows counterclockwise, while in the Southern Hemisphere, it circulates clockwise. Storms and poor weather are frequently associated with cyclones.
It varies location to location. They are known as
- Cyclones in the Indian Ocean
- Hurricanes in the Atlantic
- Typhoons in the Western Pacific and South China Sea, and,
- Willy-willies in the Western Australia.
Conditions favorable for the formation
- Large sea surface with temperature higher than 27° C;
- Presence of the Coriolis force;
- Small variations in the vertical wind speed;
- pre-existing weak low-pressure area or low-level-cyclonic circulation;
- Upper divergence above the sea level system.
- The energy that intensifies the storm comes from the condensation process in the towering cumulonimbus clouds, surrounding the centre of the storm.
- On reaching the land the moisture supply is cut off and the storm dissipates. The place where a tropical cyclone crosses the coast is called the landfall of the cyclone.
- A mature tropical cyclone is characterized by the strong spirally circulating wind around the centre, called the eye.
- Around the eye is the eye wall, where there is a strong spiraling ascent of air to greater height reaching the tropopause.
Stages of Tropical Cyclone Formation
- Tropical cyclones can be classified into three stages throughout their development:
- Formation and Initial Development Stage
- The transport of water vapor and heat from the warm ocean to the overlying air, largely through evaporation from the sea surface, is crucial to the creation and early development of a cyclonic storm.
- Convection with condensation of rising air above the ocean surface stimulates the creation of huge vertical cumulus clouds.
- Mature Stage
- The air rises in powerful thunderstorms as a tropical storm intensifies, and it tends to spread out horizontally at the tropopause level. When air spreads out, a positive pressure is created at high elevations, speeding up the downward migration of air due to convection.
- When subsidence is induced, air warms up due to compression, resulting in a warm ‘Eye‘ (low pressure centre). A mature tropical cyclone in the Indian Ocean has a concentric pattern of highly turbulent large cumulus thundercloud bands as its principal physical feature.
- Modification and Decay
- A tropical cyclone begins to weaken in terms of core low pressure, internal warmth, and extremely fast speeds.
Destruction Caused by Cyclones
Cyclones are disastrous in many ways. They do more harm than any good to the coastal areas.
1) Strong Winds
- Cyclones are known to cause severe damage to infrastructure through high-speed winds.
- Very strong winds which accompany a cyclonic storm damages installations, dwellings, communications systems, trees etc., resulting in loss of life and property.
2) Torrential rains and inland flooding
- Torrential rainfall (more than 30 cm/hour) associated with cyclones is another major cause of damages. Unabated rain gives rise to unprecedented floods.
- Heavy rainfall from a cyclone is usually spread over a wide area and cause large scale soil erosion and weakening of embankments.
3) Storm Surge
- A Storm surge can be defined as an abnormal rise of sea level near the coast caused by a severe tropical cyclone.
- As a result of which seawater inundates low lying areas of coastal regions drowning human beings and life stock.
- It causes eroding beaches and embankments, destroys vegetation and leads to the reduction of soil fertility.
Management of Cyclones in India
- In 2005, the country introduced new laws to set up what’s called the National Disaster Management Authority, a central agency charged with one thing: responding to and minimizing the impact of disasters.
A year later, in 2006, India established a National Disaster Response Force (NDRF), a specialized corps of highly trained men and women focused on disasters such as cyclones and earthquakes. It’s now comprised of almost 25,000 personnel.
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