Note4Students

From UPSC perspective, the following things are important :

Prelims level: Western Disturbances

Mains level: Not Much

disturbance

The days have been unusually warm for winter in New Delhi with the maximum temperature remaining above normal mostly on account of fewer western disturbances affecting this year.

Western Disturbances

A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
They are labelled as an extra-tropical storm originating in the Mediterranean, is an area of low pressure that brings sudden showers, snow, and fog in northwest India.
In the term “extra-tropical storm”, storm refers to low pressure. “Extra-tropical” means outside the tropics. As the WD originates outside the tropical region, the word “extra-tropical” has been associated with them.
It is a non-monsoonal precipitation pattern driven by the westerlies.
The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
Extratropical storms are global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
Western disturbances are more frequent and strong in the winter season.

Impact: Winter Rainfall and Extreme Cold

Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
They are the cause of most winter and pre-monsoon season rainfall across northwest India.
An average of four to five western disturbances forms during the winter season.

Its significance

Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.
Wheat among them is one of the most important crops, which helps to meet India’s food security.

Try this PYQ:

Consider the following statements:

The winds which blow between 30°N and 60°S latitudes throughout the year are known as westerlies.

The moist air masses that cause winter rains in the North-Western region of India are part of westerlies.

Which of the statements given above is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) Neither 1 nor 2

Post your answers here.
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