- Northwest India has seen multiple spells of rainfall due to western disturbances.
- Out of the 10 States and Union Territories of northwest India, six have recorded a large excess in rainfall so far this month, including Delhi, Uttar Pradesh, Punjab, Haryana, Rajasthan and Chandigarh.
- A western disturbance is an extratropical cyclone that originates in the Mediterranean region and provides heavy winter rain to the Indian subcontinent’s northern regions.
- A Western Disturbance is defined by as a low-pressure depression or trough over the surface or upper-air in the westerly winds regime north of 20 degrees north, causing pressure, wind pattern, and temperature fields to fluctuate.
- Cloudiness, with or without precipitation, is present.
- Low pressure usually forms over the Mediterranean Sea and moves across Iran, Iraq, Afghanistan, and Pakistan before arriving in India, where it is filled with moisture.
- These moisture-laden western disturbances finally collide with the Himalayas and become blocked.
- As a result, moisture is trapped, and precipitation is distributed across Northwest India and occasionally other portions of North India in the form of snow and rain.
- During the winter season, an average of 4-5 western disturbances emerge.
Why is it called Western Disturbance?
- The term ‘Western’ alludes to the direction they came from in India.
- Because the air in low-pressure systems is unstable or disturbed, the term “disturbance” is used.
- It was coined by Indian meteorologists to describe systems moving from west to east.
How do Western Disturbances Affect Weather?
- Most winter and pre-monsoon season rainfall in North-West India is due to Western Disturbances.
- Cloudy skies, warmer night temperatures, and unexpected rain are frequently linked with this event.
- Western disturbances are thought to account for around 5-10% of India’s total yearly rainfall.
- In the winter, western winds bring moderate to heavy rain to low-lying areas and heavy snow to the Indian subcontinent’s mountainous regions.
- Rain during the winter season is critical for rabi crops such as wheat, barley, mustard, gram, lentil, etc., one of India’s most important crops.
- Crop failure and water shortages are linked to weak western disturbances in north India.
- Farmers can benefit from strong western disturbances as it helps with water scarcity.
SOURCE: THE HINDU, THE ECONOMIC TIMES, PIB