From UPSC perspective, the following things are important :
Prelims level : Western Disturbances
Mains level : Not Much
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.
- 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.
- 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.