Explain the formation of tropical cyclones. Also, illustrate the global distribution of these cyclones.
A tropical cyclone is a low pressure system over tropical or subtropical waters, with organised convection. The winds at lower level rotate clockwise (Southern Hemisphere) and anticlockwise (Northern Hemisphere).
Formation of tropical cyclones:
- Conditions conducive for formation of tropical cyclones:
- Sea surface temperature must be greater than 270
- Presence of high moisture content in atmosphere.
- Presence of Coriolis force.
- Pre-existing condition of weak low pressure area.
- Upper air divergence above sea level.
- Process of formation:
- Formed when convection causes warm, moist air above the ocean to rise.
- The Coriolis Effect, made by earth’s rotation causes winds to rotate and warm air rises up quickly.
- This warm moist air rises up and condenses to form large cumulonimbus clouds.
- Release of energy from condensing of cumulonimbus clouds.
- Continuous supply of moisture from Ocean, strengthens the cyclone.
- Mature phase – strong spiral winds around the calm centre called ‘eye’.
- Dissipates after landfall because supply of moisture is cutoff.
- Caribbean sea, Gulf of Mexico.
- North-west Pacific Ocean.
- Pacific Ocean, west of Mexico.
- South Indian Ocean (near Madagascar)
- North Indian Ocean and Bay of Bengal.
- Arabian sea
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