Geography Answer Writing Practice 2018 - Week 3 - Question 6
90 Days Geography Answer Writing Practice Question 2 for 30-Nov-2018
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30-Nov-2018 - Question 2
Describe the origin and development of thunderstorms with examples. 15 marks
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A thunderstorm is a storm with thunder and lightning accompanied by heavy rainfall or hail.
In a the thunderstorm the air rises abruptly with great force due to which there is quick condensation and cloud formation and there is abundant absolute humidity due to the high rate of evaporate consequent upon very high temperature during summer season (edges of the Sahara desert, American midwest, Venezuela and Argentina) or due to orographic movement of air up a mountain barrier (summer season movement of air in the Himalayas). Thunderstorms are also formed at cold and warm fronts of temperate cyclones (Northern Europe, USA and Canada).
There are three stages of formation -
Towering cumulus stage - Start of formation of dark clouds.
Mature stage - Characterized by formation of cumulonimbus clouds, heavy downpour, thunder,and lightning.
Dissipating stage - The rain fall is spent and the cloud begins to dissipate with lesser rainfall progressively.
The rainfall of a thunderstorm is closely related to its numerous cells. There is maximum rainfall in the centre and minimum at the periphery of each convective cell. Fully developed cell yields rainfall for about an hour whereas weak cells die out within a few minutes.
Hail is formed when condensation occurs below the freezing point. Hail falls to the ground when the rising convection currents become weak and feeble.
Electrical discharge centres are developed in a mature thunderstorm. The centres of positive and negative charges develop in the upper and lower portion of the clouds . Lightning is produced when the electrical potential gradient between the electrical positive and negative charges becomes very steep.
Thunder is produced use to sudden and rapid expansion of air columns caused due to sudden and rapid expansion of air columns caused by the intense heat from the lightning strikes.
Squall is the downward movement and divergence of cold air at the ground surface with great velocity.
Thus, this is how thunderstorms originate and subsequently develop.