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29th October 2022 (7 Topics)

Fewer cyclones in Bay of Bengal but frequency increased in Arabian Sea


Recently a report highlighted the events of occurrence of Cyclones in the Arabian Sea has increased as compared to the Bay of Bengal over several years due to Climate Change.


What are Cyclones?

  • A cyclone is a huge strong wind system that blows around the center of an intense low-pressure area.
  • Cyclones are the local name of the Indian Ocean and the South Pacific Ocean, but in the northwest Pacific Ocean they are known as typhoons, and in the northeast Pacific Ocean and North Atlantic, they are known as
  • Since the cyclones form in the tropical region, they are also known as tropical storms, tropical revolving storms, or tropical cyclones.
  • In the northern hemisphere, cyclone winds blow anticlockwise and they reverse in the southern hemisphere.

How are they formed?

  • Tropical storms are those that form between the latitudes Tropic of Cancer and the Tropic of Capricorn and rotate in the anti-clockwise direction.
  • The surface of oceanic waters heats up due to the sun and as warm air and moisture rise up from the surface of the warm waters, more air rushes to fill the space in.
  • This air in turn rises with humidity, creating a cycle of warm, moist air rising up. This system grows in height and size, spreading out and causing a tropical cyclone.

What is the general trend of cyclones?

  • Generally, India gets 5 cyclones on average in a year.
    • 4 in the Bay of Bengal
    • 1 in the Arabian Sea
  • Cyclones occur in the pre-monsoon months of May-June and the post-monsoon months of October- November.
  • Among the cyclones that formed in the waters of the Bay of Bengal, over 58 percent approached the coast during the October-November post-monsoon season, while 30 percent did so during the pre-monsoon season.
  • On the other side, only about 25 percent of the cyclones that formed in the Arabian Sea approached the coast during both pre and post-monsoons.

The Geographic Location:

The Arabian Sea and the Bay of Bengal are both a part of the Indian Ocean, which extends on the west along the African coast and Madagascar up to the Arabian Peninsula and the Gulf of Oman, down to the North Indian Ocean below India, along the Andaman Sea, and goes all the way to the Australian coast

Bay of Bengal vs. Arabian Sea

  • Factors affecting cyclones in the Bay of Bengal: Near India, cyclones form on either side of the country, but the ones in the Bay of Bengal are more frequent and more intense than in the Arabian Sea.
  • The Bay of Bengal is fed by a constant source of freshwater in the form of giant rivers like the Ganga and the Brahmaputra.
  • The river water that empties into the Bay of Bengal warms up at the surface and rises up as moisture.
  • This makes it difficult for the warm layers of water to mix properly with the cooler layers of water below, keeping the surface always warm and ready to feed any potential cyclone over it.
  • Furthermore, because of the shape of the land around the Bay of Bengal, the winds are slower and weaker over the ocean, ready to spin.
  • Factors affecting cyclones over the Arabian Sea: Conversely, the northern, central, and western parts of the Arabian Sea have a much cooler temperatures. The mountains in east Africa direct winds toward the Arabian Peninsula, dissipating heat much more efficiently throughout the Arabian Sea.
  • As a result, this region is not favorable to feed potential cyclones and about half the cyclones that move into this area typically lose energy and dissipate.
  • However, this year, the sea surface temperatures continue to remain abnormally high, in the 30s, feeding cyclonic conditions.

The changing trend of cyclone frequency:

  • In recent years, the frequency of cyclones has increased and more than this, there is a decrease in monsoon season as well as post-monsoon season.
  • However, in the particular case of the Arabian Sea, in the last 30 years, from 1990 onwards, there is a significantly increasing trend of extremely severe cyclones. And as a result, the most intense cyclones in the region are causing a lot of devastation over the western coast of India.
  • Not only is the Arabian Sea, but the Bay of Bengal also witnessing many severe cyclones in recent times.

How climate change is contributing to the increased frequency of cyclones?

  • Climate change is increasing the damage that cyclones, cause in several ways;
    • increasing sea surface temperatures that can make cyclones more powerful,
    • increasing the rainfall intensity during the storm and
    • Rising sea levels, increase the distance inland that storm surges reach.
  • The strongest cyclones have become more common across the world and scientists project that climate change will continue to make the strongest cyclones more powerful.
  • The strength of cyclones affecting the countries bordering the North Indian Ocean has been increasing as the planet has warmed.
  • Climate change is increasing the danger from cyclones in several ways cyclones are fuelled by available heat.

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