Definition of ‘Western Disturbance’
Dr R.M. Saxena, Professional Meteorologist at Skymet Weather defines Western Disturbance as “a low pressure area or a trough over surface or the upper-air in the westerly winds regime, north of 20°N, causing changes in pressure, wind pattern and temperature fields. It is accompanied by cloudiness, with or without precipitation.”
The term Western Disturbance (WD) was coined by Indian meteorologists for describing the systems moving from the west to east direction.
Where do Western Disturbances originate from?
WDs originate in the Caspian Sea or the Mediterranean Sea as extra-tropical cyclones. They gradually travel across the middle-east from Iran, Afghanistan and Pakistan to enter the Indian sub-continent.
When are Western Disturbances the strongest?
Though WDs move across the Indian region throughout the year, they are in their peak during winter months of January and February. Their effect is minimal during the monsoon months in India.
What are the induced systems and their effect?
Induced systems are secondary low pressure areas or cyclonic circulations induced by the primary WD. Generally these are observed over central Pakistan and adjoining west Rajasthan region which gradually shift eastwards, accentuating rain over Northwest India. They also lead to rise in temperatures, fall of surface pressure, appearance of high, medium and low clouds. Normal pressure and wind patterns are restored with the moving away of the disturbance.
How do Western Disturbances affect Agriculture?
Western Disturbances along with their induced systems are the principle rain producing systems during non-monsoonal months over Northwest India including Punjab, Haryana, Uttar Pradesh and Delhi. Their effect sometime extends up to Gangetic plains and Northeast India. They are also responsible for bringing snowfall in the higher reaches of Jammu & Kashmir, Himachal Pradesh and Uttarakhand.
Are Western Disturbances important for Rabi crops?
Western Disturbance brings winter and pre-monsoon rain and is important for the development of the Rabi crop in the Northern subcontinent. Considering that wheat is one of the most important Rabi crops, which is the staple diet of people in this region, winter showers contribute to meet India’s food security.