• UGI USER
  • Oct 27, 2022
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Cyclone Sitrang kills 35 in Bangladesh

Why in News?

Bangladesh has been devastated by Cyclone Strang, which slammed into densely-populated, low-lying areas.

● Named by Thailand, Sitrang is the first tropical cyclone of the post-monsoon season of 2022.
● In 2018, Titli was the last October cyclone in the Bay of Bengal.

What are the Tropical Cyclones?

● A tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain.
● A characteristic feature of tropical cyclones is the eye, a central region of clear skies, warm temperatures, and low atmospheric pressure.
● Storms of this type are called hurricanes in the North Atlantic and eastern Pacific and typhoons in SouthEast Asia and China. They are called tropical cyclones in the southwest Pacific and Indian Ocean region and Willy-willies in north-western Australia.
● Storms rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere.
● The conditions favourable for the formation and intensification of tropical storms are:
○ Large sea surface with temperature higher than 27°C.
○ Presence of the Coriolis force.
○ Small variations in the vertical wind speed.
○ A pre-existing weak low- pressure area or low-level-cyclonic circulation.
○ Upper divergence above the sea level system.

How do Tropical Cyclones Form?

● The development cycle of tropical cyclones may be divided into three stages:
○ Formation and Initial Development Stage:
■ The formation and initial development of a cyclonic storm depends upon the transfer of water vapour and heat from the warm ocean to the overlying air, primarily by evaporation from the sea surface.
■ It encourages formation of massive vertical cumulus clouds due to convection with condensation of rising air above the ocean surface.
○ Mature Stage:
■ When a tropical storm intensifies, the air rises in vigorous thunderstorms and tends to spread out horizontally at the tropopause level. Once air spreads out, a positive pressure at high levels is produced, which accelerates the downward motion of air due to convection.
■ With the inducement of subsidence, air warms up by compression and a warm ‘Eye’ (Low pressure centre) is generated. The main physical feature of a mature tropical cyclone in the Indian Ocean is a concentric pattern of highly turbulent giant cumulus thundercloud bands.
○ Modification and Decay:
■ A tropical cyclone begins to weaken in terms of its central low pressure, internal warmth and extremely high speeds, as soon as its source of warm moist air begins to ebb or is abruptly cut off.

 

UPSC Civil Services Examination, Previous Year Questions Prelims

Q. In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason? (2015)

(a) Sea surface temperatures are low

(b) Inter-Tropical Convergence Zone seldom occurs

(c) Coriolis force is too weak

(d) Absence of land in those regions

Ans: (b)

 

Q. In the context of which of the following do some scientists suggest the use of cirrus cloud thinning technique and the injection of sulfate aerosol into the stratosphere? (2019)

(a) Creating artificial rains in some regions

(b) Reducing the frequency and intensity of tropical cyclones

(c) Reducing the adverse effects of solar wind on the Earth

(d) Reducing global warming

Ans: (d)

 

Q. Consider the following statements: (2020)

1. Jet streams occur in the Northern Hemisphere only.
2. Only some cyclones develop an eye.
3. The temperature inside the eye of a cyclone is nearly 10ºC lesser than that of the surroundings.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 and 3 only

(c) 2 only

(d) 1 and 3 only

Ans: (c)

 

Mains

Q. The recent cyclone on the east coast of India was called “Phailin”. How are tropical cyclones named across the world? Elaborate. (2013)

Q. Tropical cyclones are largely confined to the South China Sea, Bay of Bengal, and the Gulf of Mexico. Why? (2014)

Q. Discuss the meaning of color-coded weather warnings for cyclone-prone areas given by the India Meteorological Department. (2022)