Question

Difficulty: HardClimate, Weather Systems, and Monsoon of India

Consider the following statements regarding the phenomenon of Western Disturbances and their impact on Indian weather:

1. They originate as extratropical cyclones over the Mediterranean region and are steered towards the Indian subcontinent by the Subtropical Westerly Jet Stream.
2. The arrival of these disturbances is usually heralded by a sudden drop in night temperatures and clear skies over the northern plains.
3. They bring crucial winter rainfall to the north-western plains and heavy snowfall to the Western Himalayas, which is highly beneficial for the cultivation of Rabi crops such as wheat.

Which of the statements given above is/are correct?

  1. 1 and 3 onlyAnswer
  2. B
    1 and 2 only
  3. C
    2 and 3 only
  4. D
    1, 2 and 3

Answer

Statements 1 and 3 only are correct.
Statements 1 and 3 are correct. Western Disturbances are extratropical weather systems originating over the Mediterranean region that are transported into India by the Subtropical Westerly Jet Stream. They provide essential winter precipitation to the plains of north-western India and snowfall to the Himalayas, which is crucial for Rabi crops like wheat. Statement 2 is incorrect because an advance signal of their arrival is a rise in night temperatures caused by cloud cover trapping terrestrial radiation, whereas temperature drops occur after the disturbance exits.

Step-by-Step Solution

1
Evaluate Statement 1 regarding origin and mechanism.
Statement 1 is correct.
Western Disturbances are shallow extratropical depressions originating over the Mediterranean Sea, Caspian Sea, and Black Sea. They travel eastward and enter northwestern India driven by the Subtropical Westerly Jet Stream.
2
Evaluate Statement 2 regarding meteorological advance indicators.
Statement 2 is incorrect.
The advance indicator of the arrival of Western Disturbances is an increase (rise) in night temperature accompanied by cloud cover that prevents terrestrial radiation loss. Cold wave conditions and drops in temperature occur after the disturbance passes away.
3
Evaluate Statement 3 regarding rainfall distribution and economic significance.
Statement 3 is correct.
Rainfall caused by Western Disturbances in the plains (Punjab, Haryana, Western UP) and snow in the Himalayan region (Jammu & Kashmir, Himachal Pradesh, Uttarakhand) is vital for sustaining the winter (Rabi) crops, particularly wheat.

Key Concept

Western Disturbances mechanism, upper atmospheric jet stream steering, and agricultural impacts
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