Jet streams are fast-flowing, narrow air currents in the upper atmosphere, typically found near the tropopause at altitudes around 30,000 feet (9-12 km). They generally flow from west to east and are formed due to temperature differences between polar and tropical air masses

Types of Jet Streams Relevant to India

• Subtropical Jet Stream (STJ): Located around 25° to 35° N latitude, flowing west to east at high altitudes. It shifts seasonally, moving northwards during summer and southwards in winter

• Tropical Easterly Jet (TEJ): Originates from the Tibetan Plateau and flows east to west during the summer monsoon season, playing a key role in monsoon dynamics

• Polar Jet Stream: Influences western disturbances that bring winter rainfall to northern India

How Jet Streams Affect India's Climate

• Monsoon Onset and Intensity:
  The northward shift of the Subtropical Jet Stream in early June signals the onset of the Indian summer monsoon. This movement allows moist monsoon winds to penetrate India, bringing heavy rainfall. Conversely, the southward retreat of the STJ in late summer marks the withdrawal of the monsoon

• Monsoon Strength:
  The warming of the Tibetan Plateau strengthens the Tropical Easterly Jet, which supports anti-cyclonic conditions in the upper troposphere favorable for a strong monsoon. If Tibet’s warming is weak, the TEJ weakens, leading to a weaker monsoon

• Distribution of Rainfall:
  The easterly jet streams help steer tropical depressions into India, which are responsible for areas of highest monsoon rainfall

• Winter Weather:
  The polar jet stream influences western disturbances-weather systems that bring winter rain and snow to northern and northwestern India, affecting the winter climate

• Cyclonic and Anticyclonic Conditions:
  Jet streams create ridges and troughs in the upper atmosphere that correspond to high and low pressure at the surface, influencing the formation of cyclones and anticyclones. This mechanism affects the development of low-pressure systems critical for monsoon rains

In summary, jet streams are crucial atmospheric features that regulate the timing, strength, and distribution of the Indian monsoon as well as winter weather patterns, thereby significantly shaping India's climate