Prelims: Current events of national and international importance | Geography
Why in News?
The Siberian High has recently drawn attention due to its strong winter activity, influencing cold weather conditions across parts of Asia, including India.
- Siberian High – It is an intense, robust system of cold, dry air and high atmospheric pressure that controls winter weather across Eurasia.
- Location – Centered near Lake Baikal in Siberia, it's also known as the Asiatic High or Siberian anticyclone.
- Intensity – It is the strongest semi-permanent high-pressure system in the Northern Hemisphere, with pressure often exceeding 1040 millibars.
- Vertical Extent - It is a shallow system, rarely persisting above altitudes of 3,000 meters (10,000 feet).
- Nature of Air – It is extremely cold and dry air.
- Formation – Radiative Cooling - The high forms due to intense cooling of the Earth's surface over the vast Asian landmass.
- During the long winter nights, heat escapes into space, causing the air near the surface to become dense, heavy, and cold.
- Winter Peak - It reaches its maximum strength in midwinter (January/February) and drives the northeast monsoon in East and South Asia.
- Summer Dissipation- In the summer months, the system is replaced by the Asiatic Low, which brings the summer monsoon.
- Climatic Drivers of Variability - Arctic Oscillation (AO) – Arctic Oscillation (AO) / North Atlantic Oscillation (NAO)
- Negative AO → stronger Siberian High.
- Positive AO → weaker high.
- ENSO (El Niño–Southern Oscillation)
- El Niño years may weaken the Siberian High; La Niña can strengthen it (not always consistent).
- Eurasian Snow Cover - Greater autumn snow cover → stronger winter Siberian High.
- Climate Change - Arctic amplification may reduce temperature gradients, potentially weakening the Siberian High, though episodic extreme cold events may persist.
- Impact on India – Siberian High drives cold northerly winds towards India.
- It is a key reason for cool winters in North India.
- The Himalayas generally block the most extreme cold associated with the Siberian High.
- During La Niña conditions, the Siberian High can overcome the Himalayan barrier and move southward.
Reference
The Hindu | Siberian High
