Tropical cyclones

Tropical cyclones are intense circular storms that originate over the warm tropical oceans with more than 119 kilometres per hour speed and heavy rains. Mainly, the greatest damage to life and property caused not from the wind but from other secondary events including storm surges, flooding, landslides and tornadoes. Tropical cyclones are among the foremost destructive weather phenomena and also known as typhoons or hurricanes. They include a number of different hazards that can individually cause significant impacts on life and property, such as storm surge, flooding, extreme winds, tornadoes and lighting.

Tropical cyclones are known by various names in different parts of the world. In the North Atlantic ocean and the eastern North Pacific they are called hurricanes, and in the western North Pacific around the Japan, and China the storms are referred to as typhoons. In the western South Pacific and Indian ocean they are variously referred to as severe tropical cyclones, tropical cyclones, or simply cyclones. All these different names refer to the same type of storm. The tropical cyclone is formed when a transfer of water vapour and heat from the warm ocean to the overlying air occurred primarily by evaporation from the surface of the sea. As we know that warm, moist air rises, it expands and cools, quickly and become saturated and released latent heat due to the condensation of water vapour. By this process, the column of air in the core of the developing disturbance is warmed and moistened.  The temperature difference is formed between the warm, rising air and the cooler environment that causes air to become buoyant and enhance its upward movement. If the surface of the sea is too cool then there will not be enough heat available and the rate of evaporation will be low to provide fuel to the tropical cyclone. Even the supply of energy will also be cut off due to warm surface water layer is not enough deep. It happens because the tropical system modifies the underlying ocean. The sea surface becomes cool due to the falling of the rain from the deep convective clouds and the strong winds in the centre if the storm will further create turbulence. If this resulting mixing brings cool water from the below the surface layer to the surface, the fuel supply for the tropical system will be removed.

A tropical cyclone that remains over the ocean and moves into higher latitudes will change its structure and become extra tropical as it encounters cooler water. Each year the impacts of tropical cyclones and other weather, climate and water extremes around the Earth give rise to multiple casualties and significant damage to property and infrastructure, with adverse economic consequences for communities that can persist for many years. 


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