Cyclones:
Cyclones are rapid inward air circulation surrounding an area of low air pressure. In the Northern hemisphere, air circulates anticlockwise, whereas in the Southern hemisphere, air circulates clockwise.
Typically, cyclones are accompanied by violent storms and poor weather.
The term cyclone is derived from the Greek word cyclos, which refers to a snake's coils. Henry Peddington coined the term because the tropical storms in the Bay of Bengal and the Arabian Sea resemble sea serpents.
Classification of Cyclones:
Tropical cyclones and Extra Tropical cyclones (also known as Temperate cyclones or middle latitude cyclones or Frontal cyclones or Wave Cyclones) are the two types of cyclones.
The World Meteorological Organisation uses the term 'Tropical Cyclone' to describe weather systems with winds exceeding 'Gale Force' (at least 63 kilometres per hour).
In the region between the Tropics of Capricorn and Cancer, tropical cyclones form. They are large-scale weather systems that develop over tropical or subtropical waters, where they organise into wind circulation at the surface.
Extratropical cyclones are observed in temperate zones and regions of high latitude, although it is known that they originate in the Polar Regions.
Cyclones in India
Tropical Cyclones:
Tropical cyclones develop in the Bay of Bengal, Arabian Sea, and Indian ocean. The Indian Coastal States of Tamil Nadu, Andhra Pradesh, West Bengal, Odisha, and Gujarat are impacted by these tropical cyclones, which have extremely high wind speeds and heavy precipitation.
Most of these cyclones are extremely destructive due to their high wind speed and accompanying torrential rain.
There are three elements associated with cyclones that contribute to their destructive nature. Which are-
Strong Winds/Squall: It causes damage to structures, homes, communication systems, trees, etc., resulting in loss of life and property.
Heavy precipitation and interior flooding: People without shelter as a result of the cyclone face a serious problem with rain. Typically, heavy rainfall is dispersed over a large area and causes widespread soil erosion and embankment deterioration.
Storm surge is an abnormal rise in sea level close to the coast caused by a powerful tropical cyclone. Due to storm surge, seawater floods low-lying coastal regions, drowning humans and animals, eroding beaches and cliffs, destroying vegetation, and reducing soil fertility.
Impact of cyclones:
Several times, India has faced the devastation of cyclones. A cyclone has an effect on the economic and social life of a society. Some of the effects are the following:
- Cyclones cause extensive damage to the nation's properties and resources, particularly in coastal regions. Particularly for those who rely solely on fishing for sustenance and water, food and clean water are difficult to obtain.
- It diminishes the standard of living of the populace. It causes significant harm to the natural environment.
- In the aftermath of a cyclone, there is a lack of clean food, water, and shelter, which leads to death and various health complications in the community.
- There is an uncertain rise in sea level as a result of a cyclone's storm surge, heavy rainfall, and flooding, which leads to waterlogging at undesirable locations, which in turn causes severe infections and diseases.
- It destroys both private and public property by wreaking havoc on infrastructures such as roads, bridges, homes, and buildings.
- The destruction of crops has an effect on the income of farmers and, as a result, contributes to inflation, unemployment, crime, etc. The result is that the poor get poorer and the rich get richer.
- It also affects the individual's physical and mental health, as they may have lost loved ones.
- Long periods of time may be required for the development of sociodemographic, psychosocial, socioeconomic, and sociopolitical consequences.
- Economic loss such as a decline in asset value, a decrease in investment, and a decline in import and export revenues.
Cyclone Vulnerability Profile of India:
India has been hit by numerous cyclones over the years. However, nine cyclones were the most destructive and caused widespread devastation. The Indian subcontinent's 7516 km of coastline is the most affected region in the world. Cyclones affect approximately 13 coastal states and Union territories, including 84 coastal districts. Andhra Pradesh, Odisha, Tamil Nadu, Gujarat, and West Bengal are the five most susceptible states to cyclones. The most vulnerable union territory is Puducherry. The analysis indicates that the East coast is more susceptible to cyclones than the West coast.
Why Arabian Sea is becoming New Bay of Bengal?
The formation of tropical cyclones and their intensification are governed by various geophysical and thermodynamic parameters such as sea surface temperatures, sea level pressure, tropical cyclone heat potential, convective available potential energy, air temperature at height levels, relative humidity at mid-tropospheric levels and vertical wind shear – that is how winds can change their speed from the surface to the top of the atmosphere.
Of these, the parameters linked to global warming are sea surface temperatures and ocean heat content (oceans absorb nearly 93 percent of additional heat due to human activities).
Several long-term data sets indicate that sea surface temperature trends are higher over the NIO as compared to the other oceans – a rise of 0.15o to 0.2oC per decade as compared to 0.11oC in the latter. Within these trends, the values are higher for the Arabian Sea than what is observed in the Bay of Bengal.
This means that the Arabian Sea is warming at a higher rate as compared to the Bay of Bengal and has the potential of giving rise to more tropical storms in future.
One of the factors behind the slight decrease in the duration of tropical cyclones in Bay of Bengal is the long-term reduction in atmospheric humidity, which is rising at a greater rate over the Arabian Sea like its surface temperature.
According to a recent study published in Science Advances, statistical models suggest that the risk of strong tropical cyclones is expected to more than double across the globe by 2050 except for the Bay of Bengal and the Gulf of Mexico.
Strong vertical shears suppress cyclones, while weak vertical shears increase cyclones.
The India Meteorological Data (IMD)’s data for the 130-year-long study period found an average of 50.5 tropical cyclones per decade over the region comprising the Bay of Bengal in the East and the Arabian Sea in the West.
The frequency increase in very severe cyclonic storms, extremely severe cyclonic storms and super cyclonic storms in the Arabian Sea was observed during the post-monsoon months.
Arabian sea cyclones are increasing significantly. His study found that the proportion of Arabian sea cyclones has become 2:4 from 2001-2020. The frequency of Bay of Bengal cyclonic storms has slightly decreased but not to a significant extent due to the warming threshold for sea surface temperature (SST) over any ocean.
However, sea surface temperature is still gradually increasing over the Arabian sea, with some studies reporting a 0.5-0.7 degree Celsius increase of SST over the Indian Ocean. Researchers examined the Bay of Bengal tropical cyclones from 1982-2o20 and found that El Nino Southern Oscillation (ENSO) years reported more tropical cyclonic activity over the region.
This shift in tropical cyclogenesis was due to changes in sea surface temperature, humidity, force, disturbance and atmospheric instability. Despite a La Nina year, Cyclone Sitrang headed eastwards towards Southeast Asia, while during El-Nino years, the cyclones headed westwards towards the Indian sub-continent. Despite a La Nia, the Indian Ocean region had a relatively quiet cyclone season since last year.
Cyclone disaster management in India
There is a huge impact of disasters like cyclones which may be impossible to overcome. Therefore, it is necessary to mitigate such future disasters and minimize their effects. These measures may either be structural or non-structural. Such measures are possible only with the help of government interventions and public participation. Some of these measures are as follows:
Land use planning
This would avoid all the critical activities on the land of the most vulnerable areas. For example, any settlement activity on a floodplain may cause risk to the land. Such risk can be avoided by the concerned authorities through planning.
Hazard mapping
It assesses the severity of cyclones, their frequency or probability of occurrence, and intensities on a map. This helps in estimating the severity of damage in the affected region. Such maps are prepared with the help of past climatological data, history of wind speed, and frequency of flooding.
Early warning systems are one such means by which people are able to receive appropriate and timely information in a proper way before the disaster occurs in order to make quick decisions and take relevant action. The word ‘system’ is used to refer to the interplay between an array of elements aimed at facilitating communication and prompt response to protect and aid those in need. The four basic elements to which this system focuses is risk-knowledge, monitoring, response capability, and warning communication.
Engineered structures
Any structure should be made in such a way that it can withstand wind forces. For that, the selection of good sites is also very important. Hence, any public infrastructure should be engineered structures.
Cyclone shelters
Cyclone shelters are made in the area where there are recurrent cyclones. Such construction requires huge funding and hence funds are either raised from the government or external donors. For the construction of cyclone shelters, many aspects need to be taken into consideration such as the site, density of population, transport and communication services, and topography of the area.
Flood management
Flooding is the result of cyclonic storms. The flow of water can be regulated through the construction of dams, reservoirs, and channels. A public community can take the initiative in improving the drainage system through which such floods can be minimized. Flooding can also be managed by avoiding the storage of material under the shelters which may cause water drainage and by creating drainage systems around and under the shelter. The shelter floor should be made above 3 feet from the ground.
Mangrove plantation
The roots of the mangrove plant help in mitigating tsunamis, soil erosion, etc. They also protect the coastal areas from storm surges and wind which is accompanied by cyclones.
Improving vegetation cover
This helps in increasing the water infiltration capacity of the soil. The roots of the plants and trees will hold the soil intact and prevent soil erosion resulting in the prevention of floods.
Awareness program
End-to-end awareness programs are very important for the public welfare as they may help them to take action against such calamities. The department of Meteorology and Hydrology updates regularly about the upcoming cyclones and other special weather news. It is expected from the community that they are well aware of the warning signals and the sources for their protection.
About the new cyclone warning system
The new Impact-Based Cyclone Warning System was launched by the Indian Meteorological Department and the Ministry of Earth Sciences on 12th October 2020.
Features of the cyclone warning system include:
- This warning system will issue specific warnings in districts and locations which will factor in the infrastructure, local population, settlements, land use and also other elements will be disseminated and prepared.
- All the disaster management agencies will also refer extensively to geological, cartographic and hydrological data that is available for the concerned district.
- If any of the locations is to be hit by a wind up to 160 kmph, this warning system will warn about the kind of infrastructure that will likely get damaged and these can be mapped.
Its ultimate objective is minimizing economic losses and destruction of property due to cyclones that occur every year on the Indian coasts.
Advantages of New System:
This system takes into consideration all the essential aspects such as location warning mechanism, local population, settlements, use of land, and other important elements.
It is easily accessible to all the disaster management agencies to know about geological, cartographic, and district-wise hydrological data under this new mechanism.
This system warns about the strong wind and risk on infrastructure that may occur, in advance. It also provides better forecasting and tracking of cyclones.
This system has also resolved the tracking error of forecasting the cyclone.
The observational aspects of cyclone warning systems include different types of observations such as space based, upper air and surface based.
With the intention to meet the needs of Cyclone Warning Services and Marine weather services, seven Cyclone Warning Centers were established that covered the east & west coasts of our country. The three area Cyclone Warning Centres (ACWCs) are located at Chennai, Mumbai and Kolkata and other four are Cyclone Warning Centres (CWCs) which are located at Ahmedabad, Thiruvananthapuram, Visakhapatnam and Bhubaneswar.
Conclusion:
It is very important to control future natural disasters as they destroy the entire region that is being affected just in one hit. India is a disaster-prone country due to geographical factors and demographic composition.
Each disaster brings new deficiencies in Indian disaster management regimes. It’s not just the government or experts who can reduce the impact of these disasters but also civil society, NGOs, private organizations that can contribute to protecting the country from future tragedies.
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