Question

How are typhoons formed?

Answer 1

Hint:A typhoon, also known as a tropical cyclone or hurricane, is an extreme circular storm that originates in the warm tropical seas and is characterised by low air pressure, strong winds and heavy rain.

Complete answer:
Typhoons are compact, circular storms, normally some 320 km in diameter, whose winds are spinning around a low atmospheric pressure central area. This low-pressure centre and the Earth's rotation, which deflects the direction of the wind by a mechanism known as the Coriolis effect, propel the winds. As a result, tropical cyclones rotate in the Northern Hemisphere in a counterclockwise (or cyclonic) orientation, and in the Southern Hemisphere in a clockwise (or anticyclonic) direction.
The movement of water vapour and heat from the warm ocean to the overlying air, mostly by evaporation from the sea surface, provides the power for a tropical cyclone. As the humid, damp air rises, it spreads and cools, being saturated rapidly and losing latent heat from the water vapour condensation. This technique warms and moistens the air column at the centre of the emerging disturbance. The difference in temperature between the humid, rising air and the colder atmosphere allows the rising air to become buoyant, improving its upward movement further.

If the water surface is too cool, adequate heat will not be possible and evaporation rates will be too low to produce sufficient power for the tropical cyclone. If the warm surface water layer is not dense enough, energy sources will therefore be cut off and the underlying ocean will be modified by the evolving tropical climate. Rain falling from deep convective clouds will cool the surface of the water, and instability will be produced by the powerful winds at the core of the storm. The fuel supply for the tropical system would be removed if the subsequent mixing carries cold water from below the surface layer to the surface.

In order to initiate the development of a tropical system, the vertical motion of warm air is by itself insufficient. Further production will occur, however, if the humid, moist air moves through a preexisting atmospheric disturbance. The ambient pressure in the middle of the disturbance gets smaller as the rising air warms the centre of the disturbance from both the release of latent heat and direct heat transport from the sea surface.
The decreased pressure leads to an increase in surface currents, which in turn increases the flow of vapour and heat and adds to a further increase in air. In a positive feedback mechanism, the warming of the heart and the elevated surface winds thereby enhance one another.

Note:The low-pressure centre must be situated at least 500 km (300 miles) from the Equator for the creation of the rapid rotation characteristic of tropical cyclones. If the initial disturbance is too close to the equator, then the influence of the force of the Coriolis would be too limited to provide the spin needed. The Coriolis force deflects the air that is pulled into the low-pressure core of the surface, creating a cyclonic rotation.