Topics Covered:
- Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.
Western Disturbance
What to study?
For Prelims and Mains: Western Disturbances- causes, effects and significance.
Why in News? The western disturbance has brought heavy rainfall across various parts of the country.
What is Western Disturbance?
It is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the north-western parts of the Indian sub-continent. It is a non-monsoonal precipitation pattern driven by the westerlies.
Extratropical storms are a global phenomenon 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.
Formation:
Western Disturbance originates in the Mediterranean Sea as extra-tropical cyclones. A high-pressure area over Ukraine and neighbourhood consolidates, causing the intrusion of cold air from Polar Regions towards an area of relatively warmer air with high moisture. This generates favourable conditions for cyclogenesis in the upper atmosphere, which promotes the formation of an eastward-moving extratropical depression. They gradually travel across the middle-east from Iran, Afghanistan and Pakistan to enter the Indian sub-continent.
Impact:
- Plays important role in bringing moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
- This disturbance is usually associated with cloudy sky, higher night temperatures and unusual rain. This precipitation 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.
- Excessive precipitation due to this disturbance can cause crop damage, landslides, floods and avalanches. Over the Indo-Gangetic plains, it occasionally bring cold wave conditions and dense fog. These conditions remain stable until disturbed by another western disturbance. When western disturbances move across northwest India before the onset of monsoon, a temporary advancement of monsoon current appears over the region.
Sources: the hindu
