Tropical Cyclones in India

Tropical Cyclones in India
Tropical Cyclones in India

Tropical cyclones is one of the worst forms of natural disasters that has been frequently ravaging the Indian subcontinent in recent times. In 2020 alone one after the other cyclones have been hitting the Indian subcontinent, starting from Amphan (May 2020) to Nisarga (June 2020) to Nivar ( November 2020) and now Burevi.

Survey shows that regions along the coastal line of the Indian subcontinent are exposed to nearly 10% of the World’s tropical cyclones and this fact makes India one of the worst affected regions of the world, as far as tropical cyclones are concerned. 

The questions that therefore arises are what are these Tropical cyclones, how are they different from other forms of cyclones , what are the devastating impacts of these cyclones and  finally why India is one of the most vulnerable regions of the world to these cyclones. Let us try to understand them one by one.

Before understanding tropical cyclones, let us talk briefly what cyclones are.

Cyclones are large scale air masses, rotating around a region of low atmospheric pressure. They are characterized by inward spiralling winds rotating in the clockwise direction in the  Southern Hemisphere and counter clockwise direction in the northern hemisphere (due to the effect of the Coriolis Force).

The word Cyclone is derived from the Greek word “Cyclos” meaning the coils of a snake. The word was in fact coined by Englishman,  Henry Piddington, observing the shapes of the tropical storms in the Bay of Bengal and the Arabian Sea which appear like the coiled serpents of the sea.

There are basically two types of cyclones based on the geographical region of their origin. They are: the tropical cyclones and sub-tropical cyclones. The tropical cyclones. The tropical cyclones occur in the tropics i.e the region between the Tropic of Cancer and Tropic of Capricorn where as Extratropical cyclones occur within the extratropical regions of the Earth (i.e between 30° and 60° latitudes). In this article however, the discussion will be confined to tropical cyclones only and that too in the context of India.

Formation and features of tropical cyclones:

Tropical cyclones are characterized by heavy rains and high speed winds.

They are formed mostly over warm ocean surfaces (with temperatures higher than 27 degree Celsius). The warm ocean surface results in a turbulent transfer of water vapour from the ocean to the overlying atmosphere, this in turn creates an instability in the overlying atmosphere creating convection currents that causes the moist air to rise up followed by condensation of the air resulting in the formation of massive vertical cumulus clouds surrounding the centre of the storm.

The continuous supply if moisture from the oceans intensifies the storm and the convection current leads to the formation of vigorous thunderstorms  which reaches up to the tropopause level and spreads out horizontally there . As the air spreads out, a positive perturbation pressure accelerates the downward motion of air due to convection. The descending air creates a region called the “eye” of the cyclonic storm. Here the weather is calm. Surrounding the eye is the eye wall formed by a strong spiraling ascent of air, which reaches upto the tropopause level. This region is characterized by extremely high velocity winds (whose speed may reach up to 250 kmph) and torrential rainfall.  A mature tropical cyclone developing in the Indian Ocean is characterized by concentric pattern of highly turbulent giant cumulus thundercloud bands.

When the cyclone makes a landfall (landfall is the place where the cyclone crosses the coastline), or if it passes over cold waters, then it looses the supply of warm moist air and the storm begins to weaken and finally dissipates.

Tropical cyclones are known by different names in different parts of the world. They are known as typhoons in the China Sea and Pacific Ocean; hurricanes in the West Indian islands in the Caribbean Sea and Atlantic Ocean; tornados in the Guinea lands of West Africa and southern USA.; willy-willies in north-western Australia and tropical cyclones in the Indian Ocean.


Also See: Glacial Lake Outburst Floods


Devastating impacts of Tropical Cyclones:

Having discussed the formation and features of tropical cyclones let us now discuss impacts that these tropical cyclones have on the Indian subcontinent.

As we have already stated, before in this article that the coastal areas of India are exposed to nearly 10 per cent of the world’s tropical cyclones.

Surveys show that every year , on an average five to six tropical cyclones form in the Bay of Bengal and the Arabian Sea, out of which only two or three falls in the severe category.

Most of these cyclones that affect the Indian coastline originates in the Bay of Bengal. Cyclones also originate in the Arabian Sea but their numbers are  low as compared to that which originates over the Bay of Bengal region.

It is therefore not surprising, that out of the 5 states and one Union Territory that are vulnerable to hazards associated with tropical cyclones, 4 states namely, Tamil Nadu, Andhra Pradesh, Orissa and West Bengal and the Union Territory Puducherry are located on the east coast of India and only one state Gujarat is located on the west coast of India.

Now the question that arises is what makes India vulnerable to so many devastating tropical cyclones? and why greater number of tropical cyclones affect the eastern coastal regions of India as compared to the Western coastal regions of India?.

As far as the first question is concerned, the only two plausible answer that the experts in this respect are unplanned urban development and the rampant destruction of the mangrove forests to make way for these unsustainable developments. Experts have pointed out that these two factors have on one hand contributed to global warming and on the other hand because of the destruction of the mangrove vegetations, the coastal regions are being increasingly exposed to the  devastating impacts of these tropical cyclones , in particular the storm surges. In fact, One city that is still receiving the benefits of one of the last surviving open mangrove vegetation in India, i.e. the Sunderbans, is Kolkata, The most recent instances being the Cyclones Amphan (2020) and Bulbul (2019), both of which despite being extremely devastative had very low impact on the city, as compared to other city s in the eastern coast of the country because of the shielding effect of the  thick mangrove vegetations of Sunderbans.

The impact that global warming has been having on the cyclogenesis in the Northern Indian Ocean, where both Arabian sea and Bay of Bengal is located, is that the surface temperatures of these two water bodies have increased very rapidly leading to rapid intensification of the cyclones originating in these regions. Infact there are three elements  associated with these cyclones that cause large scale damage and destruction scale destruction to the coastal regions of the country:

These are strong winds (squalls), Torrential rainfalls and the resultant inland flooding and storm surges.

Squalls, which are long periods of sustained high speed winds speed  associated with the bands of thunderstorms that make up the spiral bands around the cyclone, cause severe damage to infrastructure and dwellings in the affected regions.

Torrential rainfall gives rise to large scale inland flooding on account of soil erosion causing weakening of embankments causing damage to life and property on one hand and destruction of agricultural plantations on the other hand thereby adversely impacting the economic life of the agricultural community.

The third most destructive feature tropical cyclones is abnormal rise of

sea level near the coast, known as storm surge. This storm surge causes inundation of low lying areas of coastal regions leading to loss of life and property on a largescale, erosion of beaches and embankments  and reduction in the fertility of soil in these areas.

Having discussed the adverse consequences of Tropical cyclones, let us have a look at some of the most destructive tropical cyclones that have hit Indian subcontinent over time.

Why Cyclones intensify more rapidy at Bay of Bengal than at Arabian Sea ? Info 1
Why Cyclones intensify more rapidy at Bay of Bengal than at Arabian Sea?

In November 1970, a cyclone by the name Bhola formed over the Bay of Bengal and made a landfall, on the coast of the then East Pakistan (which is now Bangladesh) and continued on into West Bengal. The cyclone at its peak generated winds with speeds up to 115mph causing severe destruction in the coastal areas and had a death toll of around 5 lakh people. It remains the deadliest tropical cyclone ever recorded and one of the world’s deadliest natural disasters.

The most intense tropical cyclone ever recorded in the Indian Ocean region, is the 1999 Odisha cyclone. The cyclone originated in the North Andaman Sea and made a landfall on the Odisha coast on October. The cyclone, at its peak generated wind speeds upto 160 mph and had a death toll of nearly 15,000 people and around $4.4 billion worth of damage.

The second most intense tropical cyclone, to make landfall in the Indian subcontinent after the 1999 Odisha cyclone is cyclone Phailin, which originated within the Gulf of Thailand and made landfall near Gopalpur, in Odisha , on October 2013. The cyclone prompted India’s biggest evacuation in 23 years with more than 550,000 people being moved  from the coastline in Odisha and Andhra Pradesh to safer places.

 The cyclone had a death toll of around 45 people and caused an estimated total losses of  around $4.26 billion.

The costliest cyclone on record in the North Indian Ocean Region, happened early this year , on May. The cyclone which was named as Amphan is one of the strongest tropical cyclone to strike the Ganges delta. It was also the first super-cyclone to have formed in the Bay of Bengal region since the 1999 Odisha cyclone. At its peak Amphan generated wind speeds between 150 mph to 160 mph.

The Coastal areas of West Bengal consisting of  East Midnapur, North 24 Parganas, South 24 Parganas, Kolkata, Hooghly and Howrah as well as Odisha were affected by the cyclone.  The storm had a death toll of around 86 people in west bengal  and 4 people in Odisha. The cyclone some parts of Tamil Nadu and  Kerala and caused over $ 13 billion of damage to infrastructure.

Devastating tropical cyclones very rarely originates in the Arabian sea region. Cyclone Gonu, which originated in the Arabian sea in the year 2007, and caused large scale death and destruction in Oman and Iran was the strongest cyclone on record in the Arabian Sea.

The reason behind so less numbers of destructive tropical cyclones originating in the Arabian sea is that the intensity of the tropical cyclones originating in the Arabian sea is reduced by the dry air coming from the desert of the Arabian Peninsula and unfavorable wind shear from the monsoon.

Bay of Bengal on the other hand has got favourable conditions for formation and rapid intensification of the cyclones. 

Firstly, the winds over the bay of Bengal have lesser speed as compared to those blowing over the Arabian sea, and thus it fails to the surface temperature of the Bay of Bengal. Besides Bay of Bengal has got a steady influx of waters from nearly 77% of India’s river systems, which along with the fact that it is more enclosed by land as compared to the Arabian sea, leads to rapid heating of the surface waters of the Bay of Bengal. This along with the fact that the Bay of Bengal receives high average rainfall creates the increased possibility of tropical cyclonic  formation and their intensification within a short period of time.  The shallower continental shelf region along the eastern coast of peninsular India makes the region more vulnerable to the most destructive tropical cyclones originating in the Bay of Bengal.

Government efforts to mitigate the impacts of the Tropical Cyclones:

Recognizing the vulnerability of the Indian coastal regions to the impacts of frequent tropical cyclones and the resultant large scale loss to life and property The Government of India has conceptualized  a comprehensive  National Cyclone Risk Mitigation Strategy, after several consultations at different levels. To give effect to give effect to the  interventions conceptualized under the strategy the Ministry of Home Affairs (MHA)  (Government of India) initiated the National Cyclone Risk Mitigation Project (NCRMP). The management of the project was transferred  to the National Disaster Management Authority (NDMA) in the year 2006. The overall objective of the Project is to undertake suitable structural and non-structural measures to mitigate the effects of cyclones in the coastal states and Union Territories of India. The structural measures include construction of cyclone shelters, cyclone resistant buildings. Road links, culverts, bridges, canals, drains, communication and power transmission networks etc. and the non-structural measures include setting up of early warning dissemination systems, management of coastal zones, awareness generation, disaster risk management and capacity building of all the stakeholders involved in the project.

Government efforts to mitigate the impacts of the Tropical Cyclones Info 2
Government efforts to mitigate the impacts of the Tropical Cyclones

The world bank assisted project  has identified 13 cyclone prone States and Union Territories(UTs),with varying levels of vulnerability for the implementation purpose.

 Also, realizing the importance of mangrove vegetations in buffering the coastal areas from the devastating effects of storm surges associated with the cyclones  Some states like Gujarat, Andhra Pradesh, Maharashtra have taken commendable initiatives to restore the mangrove  plantations in their respective states. At the national level India has decided to join The Mangroves for the future Initiative, which is a multi- country, multi sectoral, partner- led initiative to promote “investment in coastal ecosystem conservation for sustainable development”.

The Government of India has also set up 7 Cyclone Warning Centres (CWCs) covering the east & west coasts of our country. These CWC s that are present in Chennai, Mumbai , Kolkata ,Ahmedabad, Thiruvananthapuram, Visakhapatnam and Bhubaneswar has demonstrated commendable efficiency and accuracy in cyclonic forecasts in the cases of Phailin (2013), Hudhud (2014), Vardah (2016), Titli (2018), Fani & Bulbul(2019) and Amphan&Nisarga(2020), drastically reducing the toll on life and property.

Issues with the mitigation of cyclonic disasters:

Inspite  of the presence of all these commendable initiatives at the state and national levels, the mitigation efforts and management of cyclone related disasters are yet to achieve full proof efficiency. Several loopholes are yet to be addressed.

Firstly, disaster Management in India is largely confined relief works. This means that more focus is usually given on the management of disaters than on prevention of the disaster.

Secondly, the people living in the coastal areas, mostly belong to the marginalized communities and are therefore ill-prepared to cope up with the disaters associated with cyclones. A considerable lack of awareness regarding the impact and magnitude of the disasters have been observed  in these people.

Last but not the least issues with communication and coordination between the agencies involved in disaster management and mitigation has been observed again and again. The protests that occurred in Kerala, in the aftermath of the Cyclone Okhi disaster (2017) regarding the delayed response of the agencies involved in the mitigation of the disaster, is an example of this.

Conclusion and Wayforward:

In recent times Tropical cyclones have become one of the most frequent disasters, that the Indian subcontinent and in particular the regions located in and around the eastern coast of India has been facing. Studies have revealed that losses due to natural disasters account for nearly 2 % of India’s GDP  and nearly 12 % of the central Government’s revenue.

The increasing global temperatures are creating conditions conducive to more and more cyclogenesis and seeing the trend of the last few years it is quite evident that Tropical cyclonic disasters are poised to become more frequent and more deadly and destructive in the near future.

It is therefore imperative that the loopholes present in the Disaster management infrastructure of India is addressed at the earliest, to prevent Tropical cyclones from becoming an unmanageable natural disaster.

The robust disaster management system developed by the Government of Odisha after the 1999 super cyclonic disaster, can serve as an effective guideline and an interesting case study to prepare a fool proof disaster management infrastructure for the country especially in relation to management of cyclonic disasters.

Learning from the devastating impacts of the 1999 super cyclone, The Government of Odisha have taken some commendable initiatives to reduce the destructive impacts of cyclonic disasters, including creation of large number of cyclone shelters where the people living in the coastal may be moved in case of any cyclonic outbreak, setting up efficient and robust disaster response protocols, to be followed as soon as the early warning systems signal an imminent cyclone among many others.  



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