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Hotter oceans spawn super cyclones

Topics Covered: Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.

Hotter oceans spawn super cyclones

What to study?

For Prelims and Mains: Tropical Cyclones- formation, factors responsible, why eastern coast is more vulnerable and related information.

Context: Super cyclone Amphan that is barrelling towards West Bengal is the strongest storm to have formed in the BoB since the Super Cyclone of 1999 that ravaged Paradip in Odisha.

Cyclone Amphan intensified from a category-1 cyclone to category-5 in 18 hours, an unusually quick evolution.

Factors responsible for the intensification of cyclones in BoB:

Higher than normal temperatures in the Bay of Bengal (BoB) may be whetting ‘super cyclones’ and the lockdown, indirectly, may have played a role.

  1. Cyclones gain their energy from the heat and moisture generated from warm ocean surfaces. This year, the BoB has posted record summer temperatures a fall-out, as researchers have warned, of global warming from fossil fuel emissions that has been heating up oceans.
  2. Lockdown impact: Reduced particulate matter emissions during the lockdown meant fewer aerosols, such as black carbon, that are known to reflect sunlight and heat away from the surface.

General factors responsible for the origin of Cyclones in Bay of Bengal region 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.
  5. Upper divergence above the sea level system.

Arabian Sea is comparatively less prone to cyclonic storms than Bay of Bengal:

Temperature: BOB is hotter than Arabian sea. Hot water temperature is the basic criteria for the development & intensification of cyclones.

Salinity: Arabian sea has higher salinity than BOB. It’s easier to heat & simultaneously evaporate water having lower salinity.

Location: The typhoons originating in the Pacific Ocean too influences the cyclones in BOB, not the case in Arabian Sea.

Movement: According to IMD cyclones originating in Arabian Sea are believed to move northwest. So they actually move away from Indian mainland.

The Bay receives higher rainfall and constant inflow of fresh water from the Ganga and Brahmaputra rivers. This means that the Bay’s surface water keeps getting refreshed, making it impossible for the warm water to mix with the cooler water below, making it ideal for a depression.

InstaThink:

Prelims Link:

  1. Factors responsible for the genesis of cyclones.
  2. Naming of cyclones in various regions of the world.
  3. Why more cyclones in Eastern coast of India?
  4. What is coriolis force?
  5. What is latent heat of condensation?

Mains Link:

Discuss the factors responsible for the formation of tropical cyclones.

Sources: the Hindu.