Shifting Nature of Western Disturbances: UPSC Current Affairs

Description

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Picture Courtesy: THE HINDU

Context

A powerful Western Disturbance is causing Himalayan snowfall, temperature shifts on the North Indian plains, and poor air quality in Delhi.

What are Western Disturbances (WDs)?

Western Disturbances (WDs) are extratropical storms originating in the Mediterranean region that travel to the Indian subcontinent via the subtropical westerly jet stream.

Meteorological Impacts of the WD

Precipitation & Water Security

Winter Rain: WDs are the main source of non-monsoonal rainfall in North and Northwest India, contributing 5–10% of India's total annual rainfall.
Himalayan Snow: They provide snowfall to the Western Himalayas, maintaining glacier mass balance and feeding perennial rivers like the Indus and Ganges.
Rabi Crop Support: The moisture is vital for the growth of winter crops such as wheat, mustard, and barley.

Temperature & Visibility

Before Arrival: Cloud cover traps heat, causing a rise in night-time temperatures.
After Departure: Clear skies allow cold winds from the mountains to rush in, leading to a sharp drop in temperatures, cold waves, and dense fog.

Extreme Weather Events

Natural Hazards: Intense WDs can trigger landslides, avalanches, and flash floods in mountainous regions.
Thunderstorms & Hail: Interactions with local moisture from the Arabian Sea often result in severe hailstorms and lightning, which can damage standing crops.

Climate Change Variations

Weakening Trends: Recent studies show a falling trend in WD frequency during winter, which is linked to decreased winter lightning and drought-like conditions.
Increased Intensity: While less frequent, individual events are becoming more intense and unpredictable due to a warming atmosphere holding more moisture.

Deteriorating Air Quality

Calm winds and high humidity, before a Western Disturbance, trap local vehicular and industrial pollutants, worsening Delhi's Air Quality Index (AQI) to the 'poor' category.

Way Forward For India

Enhance Early Warning Systems

Better preparedness under the Disaster Management Act, 2005 requires investing in advanced Doppler radars and weather modeling to improve heavy precipitation forecast accuracy.

Adopt Integrated Air Quality Management

Shift from reactive measures like Graded Response Action Plan (GRAP) to a sustained, year-round strategy addressing root causes like emissions and stubble burning through interstate coordination.

Promote Climate-Resilient Agriculture

Promote resilient crop varieties; strengthen Pradhan Mantri Fasal Bima Yojana (PMFBY) to shield farmers from weather losses.

Ensure Sustainable Himalayan Development

Himalayan infrastructure must factor in climate risks, aligning with the Ravi Chopra Committee's recommendations for balancing development and ecology.

Learn Lessons from Global Practices

Infrastructure Management: Countries like Switzerland offer benchmarks in avalanche management and road clearance protocols for mountainous regions.
Pollution Control: Beijing's successful long-term action plan to combat air pollution provides a model for initiatives like India's National Clean Air Programme (NCAP) (Source: UNEP Report)

Conclusion

The recent weather events in North India highlight the urgent need for a cohesive policy framework to strengthen forecasting, manage air quality, and build agricultural climate resilience, to ensure a sustainable future.

Source: THE HINDU

Attempt Daily Quiz

PRACTICE QUESTION

Q. The term 'Chillai-Kalan', often seen in the news, refers to:

(a) A traditional harvest festival in Himachal Pradesh.

(b) The harshest 40-day period of winter in Kashmir.

(d) A government scheme for managing snowfall on national highways.

Answer: (b)

Explanation:

Chillai-Kalan is a Persian term meaning "major cold". It refers to the most severe phase of winter in the Kashmir Valley, which begins on December 21 and concludes on January 30 or 31 each year.

Frequently Asked Questions (FAQs)

A Western Disturbance is an extratropical storm originating in the Mediterranean region. It is a low-pressure system that travels eastward, propelled by the subtropical westerly jet stream, gathering moisture along the way. When it reaches the Himalayas, it releases this moisture as rain in the northern plains and snow in the mountains, primarily during the winter season.

Climate change, particularly the rapid warming of the Arctic (Arctic Amplification), is making Western Disturbances more erratic. It is causing them to become more frequent in summer, less predictable in winter, and is shifting precipitation from gentle, prolonged spells to short-duration, high-intensity events, leading to cycles of long dry spells and sudden downpours.

Arctic Amplification is the phenomenon where the Arctic region is warming two to three times faster than the global average. This reduces the temperature difference between the poles and the tropics, which in turn weakens and slows down the jet stream. Since the jet stream steers Western Disturbances, its wavier and slower path directly influences the track, intensity, and timing of WDs reaching India.