Why in the news?

  • The India Meteorological Department (IMD) has issued an ‘orange’ alert for dense to very dense fog, cold wave conditions in North India ahead of Chill-e-Kalan.

Cold Wave

  • Definition: A cold wave is a meteorological phenomenon characterized by a sudden and significant drop in temperature over a short period, typically associated with the intrusion of cold air masses into a region.
  • Features of a Cold Wave:
    • Rapid Temperature Decline: A noticeable drop in temperature over a few hours to days.
    • Duration: Can last from a few days to several weeks.
    • Regional Variation: The temperature threshold for a cold wave varies depending on the climatic norms of the region.
    • Associated Weather Conditions:
      • Strong winds.
      • Clear skies, which often exacerbate cooling during the night.
      • Formation of frost, freezing rain, or snow in some cases.
  • Causes of Cold Waves:
    • High-Pressure Systems: Cold air masses from polar or arctic regions are pushed towards lower latitudes by high-pressure systems.
    • Jet Stream Shifts: A dip in the jet stream can allow cold polar air to move southward into warmer regions.
    • Snow and Ice Cover: Reflects sunlight, reduces heat absorption, and contribute to colder temperatures.
    • Geographic Features: Valleys, mountains, and open plains can influence how cold air pools and moves.
  • Impact of Cold Waves:
    • Human Health
      • Hypothermia and frostbite risks.
      • Increased mortality rates among vulnerable populations (e.g., elderly, homeless).
    • Agriculture
      • Crop damage and reduced yield.
      • Livestock fatalities due to extreme cold.
    • Infrastructure
      • Frozen water pipes.
      • increased demand for heating, leading to energy shortages.
      • Disruption to transportation systems (e.g., icy roads, rail, and air travel delays).
    • Ecosystems
      • Stress on wildlife, affecting their survival and migration patterns.

Chill-e-Kalan

  • What is it?: Chillai-Kalan (or Chilla-i-Kalan) is the local name for the harshest, 40-day peak of winter in the Kashmir Valley.
  • Features: Temperatures drop below freezing, with frequent heavy snowfall that replenishes glaciers and reservoirs essential for summer water supply. Nights remain intensely cold, while daytime highs stay in single digits, often accompanied by fog and overcast skies.

Source: Indian Express

 

📄 Download PDF