What is the contribution of Jet Stream in the effectivity of South-West Monsoon?

Role and Contribution of Jet Streams in the Effectivity of the South-West Indian Monsoon:

Upper-tropospheric Jet Streams (flowing at 9–14 km altitude) act as dynamic atmospheric triggers governing the onset, strength, and spatial distribution of the Indian South-West Monsoon:

• 1. Subtropical Westerly Jet Stream (STWJ) Withdrawal as Trigger of Monsoon Burst:
  • During winter and spring, the STWJ bifurcates around the Tibetan Plateau, with its southern branch flowing south of the Himalayas over northern India, acting as a high-pressure dynamic cap suppressing monsoonal ascent.
  • In early June, summer heating forces the southern branch of STWJ to suddenly withdraw north of Tibet, creating a dynamic low-pressure suction vacuum that triggers the explosive "Burst of the Indian Monsoon".
• 2. Tropical Easterly Jet Stream (TEJ) as Monsoon Accelerator:
  • Intense summer heating of the high Tibetan Plateau ($>4,500 ext{ m}$) generates a thermal anticyclone aloft, creating the powerful Tropical Easterly Jet (TEJ) flowing southwest across Peninsular India towards Somalia at 100–150 hPa.
  • TEJ descends over the Mascarene High (Madagascar) in the south Indian Ocean, intensifying the maritime high-pressure cell and accelerating the South-West Monsoonal air mass directly into the Indian subcontinent.
• 3. Steering Monsoon Depressions: TEJ guides low-pressure monsoon depressions from the Bay of Bengal deep into Central India, ensuring widespread monsoon rainfall.