Factors Related to Air Pressure and Wind

India’s climate and weather patterns are largely shaped by different atmospheric conditions.

Here’s an organized breakdown:

Distribution of Air Pressure and Winds

Surface Pressure and Winds:

• Winter Conditions: In India, winter weather is influenced by high-pressure systems originating from Central and Western Asia.
• High-Pressure Center: Develops north of the Himalayas, generating a flow of dry, continental air masses towards the Indian subcontinent.
• Air Mass Interaction: These continental winds encounter trade winds over northwestern India, occasionally shifting east to the middle Ganga valley.
• Influence: Northwestern and northern India, extending to the middle Ganga valley, experiences dry northwestern winds.

Jet Stream and Upper Air Circulation

Upper Air Circulation:

• Westerly Flow: Dominated by westerly winds at altitudes of 9-13 km (Troposphere), flowing from west to east.
• Jet Streams: Located around 27°-30° North latitude, also known as subtropical westerly jet streams.
• Bifurcation: In winter, the jet stream splits into two branches:
  • Northern Branch: Flows north of the Tibetan highlands.
  • Southern Branch: Moves eastward south of the Himalayas, greatly influencing winter weather in India.
• Speed: Jet stream speeds range from about 110 km/hr in summer to approximately 184 km/hr in winter.

Western Cyclonic Disturbances and Tropical Cyclones

• Western Cyclonic Disturbances:
  • Origin: Carried by the westerly winds from the Mediterranean region.
  • Influence: Primarily affects the weather of north and northwestern India during the winter months.
• Tropical Cyclones:
  • Origin: Develop over the Bay of Bengal and the Indian Ocean.
  • Impact: Part of the easterly flow, affecting coastal regions including Tamil Nadu, Andhra Pradesh, and Odisha.
• Characteristics: Known for high wind speeds and heavy rainfall, leading to significant destruction.