Answer Synopsis 15/12/2020

Question :Indian coastal areas were recently threatened by different cyclones like Amphan and Nivar. Enlist the factors influencing the origin and development of tropical cyclones and why Bay of Bengal remains constant source of cyclones?

Structure of the answer

  • A brief background on cyclone prone nature of Indian coastal areas would do as the introduction.
  • Point out the factors behind the origin and development of tropical cyclones.
  • Mention the reasons Why Bay of Bengal is the constant source region of cyclones

Synopsis
A tropical cyclone is a weather phenomenon that is essentially a rapidly rotating storm system with characteristics such as a low-pressure center, strong winds and thunderstorms that produce heavy rain, among others.

  1. Indian sub-continent is the worst affected region of the world, having a coast line of 7516 kms. (5400 kms along the mainland, 132 kms in Lakshadweep and 1900 kms in Andaman and Nicobar Islands) is exposed to nearly 10% of the world’s Tropical Cyclones.
  2. 40% of the total population lives within 100 km of coastline.
  3. Four States (Andhra Pradesh, Odisha, Tamil Nadu, and West Bengal) and one UT (Pondicherry) on the East Coast and One State (Gujarat) on the West Coast are more vulnerable to cyclone disasters

Factor influencing the origin and development of tropical cyclones

The conditions favourable for the formation and intensification of tropical cyclones are:

  1. Large sea surface with temperature higher than 27° C;
  2. Presence of the Coriolis force enough to create a cyclonic vortex
  3. Small variations in the vertical wind speed;
  4. A pre-existing weak low-pressure area or low-level-cyclonic circulation is must for cyclone formation in tropics
  5. Upper divergence above the sea level system

Why More Cyclones are formed in Bay of Bengal?

  • There are other coastlines around the world that are vulnerable to surging storms – the Gulf Coast of Louisiana, for example – but the “north coast of the Bay of Bengal is more prone to catastrophic surges than anywhere on Earth”.
  • Both the Bay of Bengal and the Arabian Sea are prone to Cyclonic storms, but Cyclonic activities are more intense and frequent in Bay of Bengal Compared to the Arabian Sea
  1. High sea surface temperatures along with high humidity due to higher rainfall in the Bay of Bengal, triggers extremely strong cyclones.
  2. Sluggish winds, along with warm air currents in the Bay of Bengal keep temperatures relatively high.
  3. The supply of constant inflow of fresh water from the Ganga and Brahmaputra rivers makes it impossible for the warm water to mix with the cooler water below.
  4. Cyclonic winds easily move into the Bay of Bengal due to the presence of moisture source from rivers and the absence of any large landmass unlike the Arabian Sea, where Cyclones usually weaken due to the presence of Western Ghats.
  5. Whereas Arabian Sea receives stronger winds that help dissipate the heat, and the lack of constant fresh water supply helps the warm water mix with the cool water, reducing the temperature.

Indian government has envisaged many schemes to overcome the devastating effects of cyclones. Recently these efforts were tested by cyclones namely Amphan, Nivar and Barevi.

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