Which of the following statements most accurately explains the nature, dynamics, and regional implications of jet streams, particularly in the context of South Asian monsoon behavior and extreme weather events?
Show answer & explanation
Correct answer: C
Explanation
Solution: The correct answer is The Subtropical Westerly Jet retreats northward during summer, allowing the Tropical Easterly Jet to dominate, which aids monsoon onset, whereas the presence of STWJ over India during summer can suppress monsoon activity.
Explanation:
☛ Jet streams are narrow bands of strong, high-velocity winds that blow in the upper troposphere (around 9 to 12 km altitude).
☛ During winter, the Subtropical Westerly Jet (STWJ) is bifurcated by the Tibetan Plateau; its southern branch blows across northern India south of the Himalayas.
☛ In summer, due to intense heating of the Tibetan Plateau, the southern branch of the STWJ abruptly withdraws northward past the Himalayas into Central Asia.
☛ This northward shift creates low-pressure conditions over northern India and facilitates the establishment of the Tropical Easterly Jet (TEJ) near 14°N latitude.
☛ The presence of the TEJ stimulates the onset and intensification of the southwest monsoon, whereas if the STWJ lingers south of the Himalayas into early summer, it causes a delay in monsoon arrival or creates drought-like conditions.
Extra Exam-Relevant Facts:
☛ Subtropical Westerly Jet Stream (STWJ): Steers Western Disturbances originating in the Mediterranean region toward north and north-western India during winter months.
☛ Tropical Easterly Jet (TEJ): Associated with the heating of the Tibetan Plateau and helps guide tropical depressions from the Bay of Bengal into the Indian mainland.
☛ Polar Front Jet Stream: A strong upper-level westerly wind that influences mid-latitude weather systems, cyclogenesis, and frontal activity.
☛ Discovery: The concept of high-altitude jet streams was experienced and documented widely by military aviators during World War II.
Important One-Liners for Upcoming Exams:
☛ Which layer of the atmosphere contains the jet streams? → Upper Troposphere
☛ Which atmospheric phenomenon brings winter precipitation to northwest India? → Western Disturbances
☛ Which elevated plateau acts as a thermal engine for the Tropical Easterly Jet? → Tibetan Plateau
☛ In which direction do westerly jet streams typically flow? → From West to East
☛ What average wind speed can polar jet streams achieve during winter? → Exceeding 120 to 150 km/h