Tropical Cyclones (Chakrawat) in India :

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Why in News ?

Recently, Cyclone ‘Amphan‘ and ‘Nisarg’ wreaked havoc in the eastern coastal states West Bengal & Odisha and in the western coastal states Maharashtra & Gujrat – of India. 

Amphan and Nisarg both are tropical cyclone, IMD (Indian Meteorological Department) reported cyclone ‘Amphan’ with wind speed more than 222 km/hr and it hits coast of the West Bengal and Odisha. Amphan origineted in the Bay of Bengal. 

While cyclone ‘Nisarg’ with wind speed more than 110 km/hr and it hits coast of the Maharashtra and Gujarat.


Tropical Cyclones : 

CYCLONES are define as irregular wind movement having low pressure in centre and high pressure at peripheri. These are associated with destructive and violent weather condition that is very high amount of rainfall along with wind velocity. It is appear between 5 degree latitudes to 35 degree latitudes.

Condition for Cyclones Formation :

• Differential heating of land and sea.
• High-speed winds rotating around a low pressure area.
• Calm area at eye/centre of the cyclone and high speed wind at periphery.
• Cyclones can only occur beyond 5 degree latitudes.
• The energy sources are latent heat of condensation and air masses.
• Cyclone move cyclone in Northern hemisphere is anticlockwise and in Southern hemisphere is clockwise.

Two Types of Cyclone :

1. Tropical Cyclones

Tropical Cyclones :

                                  Tropical cyclones are are violent storms that originate over ocean in tropical areas and move over to the coastal area bringing about large-scale destruction caused by violent winds, very heavy rainfall and storm surges. This is one of the most devastating natural calamities they are known as cyclone in the Indian Ocean. Hurricane in the Atlantic, Typhoons in the Western Pacific South China sea, and Willy willies in the Western Australia.
Tropical cyclone founded in between 5 degree north and South to 25 degree north and South latitudes. Its covers smaller geographical area and velocity is very high in general 200 to 400 km per hour/ it can be increased upto 1300 km per hour.

Characteristics of Tropical Cyclone :

* The Central area of tropical cyclone is known as ‘Eye’ of the Cyclone.

*The diameter of tropical cyclone varies from 150 to 500 km and vertically from surface to about 12 km.

* The isobar of tropical cyclones are circular in shape and pressure gradient is very steep.

* Tropical cyclones move from east to west under the influence of trade wind.
* They give torrential downpour.
* In tropical region give very high rainfall in shorter time.
* The centre of tropical cyclone is known as ‘Eye’ of cyclone where the rainfall wind clouds are ineffective.
* Tropical cyclone source of energy is latent heat of condensation.
* Tropical cyclone source fever variety of clouds for example cumulonimbus ☁️.
* Tropical cyclone not marked by distinct stages and destructions or dissipation comes with encounter cold current are land mass.
* Tropical cyclones move from east to west due to trade wind.

* They occur in Northern hemisphere in the autumn season.

The favourable condition for formation of Tropical Cyclones :

• Large sea surface with temperature higher than 27 degree Celsius.
• Presence of the Coriolis force.
• Small variations in the vertical wind speed.
• A pre-existing weak-low-pressure area or low-level-cyclonic circulation.
• Upper divergence above the sea level system.

Indian Context ( Tropical Cyclones “Chakrawat”) : 

The diameter of the storm over the Bay of Bengal, Arabian sea and Indian ocean is between 600 to 1200 km. The system moves slowly about 300 to 500 km per day. The cyclone creates storm surges and they inundate the coastal low lands the storm Peter out on the land.
Majority of the cyclone affecting India originate from the Bay of Bengal striking the eastern coast. The ratio of tropical cyclone occurred in between Bay of Bengal and Arabian sea is 4:1.
Cyclones occurring from June to September affecting Odisha and West Bengal.
Cyclone occuring from October to December is affecting Tamil Nadu Andhra Pradesh Odisha and West Bengal.
Recent cyclones like Fani, Ockhi, Phailin etc caused loss of  property and life.

Classification of Tropical Cyclones : 

The criteria followed by Meteorological Department of India (MDI) to classify the low pressure system in the Bay of Bengal and in the Arabian Sea as adopted by World Meteorological Organisation are as under :
* Low Pressure area : wind speed less than 17 knots (<31kmph).
* Depression : wind speed from 17 to 27 knots (31 to 49 kmph).
* Deep Depression : wind speed from 28 to 33 knots (50 to 61 kmph).
* Cyclonic Storm : wind speed from 34 to 47 knots (62 to 88 kmph).
* Severe Cyclonic Storm : wind speed from 48 to 63 knots (89 to 118 kmph).
* Very Severe Cyclonic Storm : wind speed from 64 to 119 knots (119 to 221 kmph).
* Super Cyclonic Storm : wind speed above 119 knots (more than 221 kmph)

Cyclones & their Impact in India :

* India is highly vulnerable to natural disasters especially cyclones, earthquakes, floods, landslides, and droughts. Natural disaster cause a loss of 2% of GDP (Gross Domestic Products) every year in India and up to 12% of Central Government revenue.
* Indian subcontinent is the worst affected region of the world, having a coast line of 7516 Kms.
* There are 13 coastal States or UTs encompassing 84 coastal district to nearly 10% of the world tropical cyclones (At East Coast – 4 States Andhra Pradesh, Odisha, Tamil Nadu, West Bengal and One UT Pondicherry  and  on West Coast  Gujrat most vulnerable to Cyclones disasters.
* Out of the cyclones that developed in the Bay of Bengal for 58% approach and cross the East coast in October and November. Only 25% of the cyclone that develop over the Arabian Sea approach the West coast.
* Cyclones accounts for the large number of death, loss of livelihood opportunities, loss of public and private property, and severe damage to infrastructure does seriously reversing the developmental gain at regular intervals.
* Climate change and its resultant sea level rises can significantly increased the vulnerability of coastal population.

Despite the huge loss of property, animals and human life during the cyclone, there are some advantage of tropical cyclones :
• The streams are flushed of pollution.
• They add moisture to dry soil conditions.
• The local water bodies are restored.
• These Precipitation help to maintaining the water budget
• The rainfall recharges ponds, lakes underground water table.
• Carry heat and energy away from the tropics and transport it towards temperate latitudes, thus help to maintain equilibrium in the Earth troposphere.
• Maintain a relatively stable and warm temperature worldwide.

3 Prime category for Disaster (Cyclone) & Management in India :

1. Pre- Phase –
* Prevention
* Mitigation
* Preparedness
These steps taken before the the natural hazard of Cyclones. It include long-term prevention measures like construction of embankment to prevent flooding increasing plantation for reducing occurrence of landslide & sound environment management.
cyclone can also be mitigate through various short-term measures which either reduce our modify the scale and intensity of the thread improve the durability and capacity of elements at risk, e.g. proper maintenance of drainage system, better awareness and public education to reduce the risk of hazards, etc.

2. During Cyclones –
* Evacuation
* Search
* Rescue
During the cyclone, require speedy response to elevate and minimise suffering and losses. The evacuation, Search and rescue followed by provision of basic needs such as food clothing, shelter, medicine, and other necessity essential to bring the life of effective community back to degree of normalcy.

3. Post Cyclonic Phase –
* Recovery : to achieve early recovery and reduce vulnerability and future risk.
* Rehabilitation : includes provision of temporary public utilities and housing as interim measure to assist long-term recovery.
* Reconstruction : include construction of damaged infrastructure and habitats and enabling sustainable livelihoods.

Government steps against Cyclone :

According to the Home Ministry, 8% of total area in India is prone to cyclones.

* Indian Meteorological Department (IMD) is nodal agency for early warning of cyclones and floods.
* National Cyclone Risk Mitigation Project (NCRMP) launch by Ministry of Home Affairs to upgrade the forecasting, tracking and warning about cyclone in states.

*Natural Disaster Management Authority is mandatory to deal with the disaster management in India.

* Better coordination between Centre and State government.

* To prepare communities to cope with disaster, NDMP emphasizes and created need for information education and communication activities.


Way-Forward  against Cyclones in India :

There are many structural and nonstructural measures for effective disaster management of cyclones.
 The Structural Measures include the construction of cyclone shelters, construction of cyclone resistant buildings, road links, bridges, canals, drains, saline embankment, surface water tanks, communication and power transmission networks etc. (e.g. Mangrove minimise devastation to human settlements, flora and fauna from Cyclones). &
The Non-structural Measures like early warning dissemination systems, management of coastal zone, awareness generation, and disaster risk management, and capacity building of all the stakeholders involved.
These measures are being adopted and taken on the state to state basis under National Cyclone Risk Mitigation Project  (NCRMP) being implemented through World Bank Assistance.
There should be more active Participatory Democracy (Effective coordination among Centre, State, & Local levels of Government) for reducing impact of disasters.


NATURAL CALAMITIES IS UNPREDICTABLE. INDIA SHOULD PREPARE TO MITIGATE AND DEFLECT THE DESTRUCTION CAUSED BY CYCLONES FOR THIS INDIAN NEED TO MODERN TECHNOLOGIES COOPERATION AND COORDINATION BETWEEN NOT ONLY AT CENTRE AND STATE BUT ALSO AT COMMUNITIES LEVEL. IT WILL PROMOTE PARTICIPATORY DEMOCRACY TO FIGHT AGAINST CYCLONE OR DISASTER PRONE AREA.


Summary :
Devastating natural calamities.
Appear between 5 degree to 35 degree latitudes.
Some Benefits like restore water in draught area.
Government steps.
Unity among people.


References :
E-book &
https://ncrmp.gov.in/cyclones-their-impact-in-india/

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