Daily Mains Question – GS 1 – 8th July 2025
- TPP
- Jul 8
- 4 min read
Welcome to your daily Mains Model Answer — designed to deepen your grasp of Physical Geography, a vital segment of GS Paper 1. Today’s answer explores the dynamic phenomenon of Jet Streams, high-altitude westerly winds that play a pivotal role in shaping global weather systems, regional climate patterns, and even international aviation routes.
This theme bridges core concepts in atmospheric circulation, seasonal climatology, and applied geography, with direct implications for India's monsoonal behaviour, extratropical storm development, and modern transportation efficiency. By examining the formation, characteristics, and variability of jet streams, aspirants gain insight into how thermal gradients and Earth’s rotation generate and steer these powerful upper-atmospheric winds.
Understanding jet streams also has real-world significance, as their strategic use by aviation industries helps optimize fuel efficiency, reduce flight durations, and manage turbulence-related risks — showcasing the intersection between natural forces and technological adaptation. A solid command of this topic strengthens conceptual clarity and enhances your ability to link physical processes with human applications in answer writing.
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QUESTION
Discuss the formation, characteristics, and seasonal variability of jet streams. How does modern aviation strategically utilises these atmospheric currents, citing their benefits and potential hazards?
Answer: Jet streams are narrow bands of swiftly moving westerly winds found in the upper levels of the troposphere, generally between 9 km and 16 km above the Earth's surface. These high-altitude winds can attain speeds exceeding 320 km/h and play a crucial role in global atmospheric circulation. Jet streams exhibit significant seasonal variability, influencing weather systems, monsoon dynamics (especially in the Indian subcontinent), and aviation operations worldwide.
Formation of Jet Streams
Jet streams are primarily formed due to the interplay of differential solar heating and the Coriolis effect resulting from Earth’s rotation:
Temperature Gradient: The equator receives more solar radiation than the poles, creating a steep pressure gradient between tropical and polar regions.
Coriolis Force: As air moves from high to low pressure, Earth’s rotation deflects these winds, causing them to flow from west to east.
Tropopause Discontinuity: At the boundary between the troposphere and stratosphere (called the tropopause), this pressure and temperature gradient is sharpest, favouring the formation of high-speed geostrophic winds, i.e., jet streams.
Jet streams are essentially geostrophic winds that flow parallel to isobars at high altitudes.
Characteristics of Jet Streams
Feature | Description |
Location | Found near the tropopause, typically between 9–16 km altitude |
Direction | Flow from west to east in both hemispheres |
Width | Usually 100 to 500 km wide |
Thickness | Vertical depth ranges from 1 to 3 km |
Speed | Average speed: 160–320 km/h, can reach up to 400 km/h in winter |
Core | The strongest winds are concentrated in a narrow core known as the jet streak |
Path | Highly meandering, often resembling Rossby Waves (planetary waves) |
Temperature Gradient | Positioned along the boundaries of cold and warm air masses, such as the polar front |
Types of Jet Streams
Polar Front Jet Stream (PFJS):
Located at 50°–60° N and S latitude.
Influences mid-latitude weather patterns and cyclogenesis.
Subtropical Jet Stream (STJS):
Found at 25°–30° latitude.
Stronger during winter; affects Indian monsoon withdrawal.
Tropical Easterly Jet Stream (TEJS):
Develops during the Indian summer monsoon.
Located near 15°N, typically between July and August.
Associated with strong monsoonal rainfall in central India.
Polar Night Jet Stream:
Forms during polar winter above 20 km altitude due to intense cooling.
Seasonal Variability of Jet Streams
Jet streams exhibit marked seasonal shifts:
Winter:
Jet streams are stronger, broader, and positioned closer to the equator.
Due to greater temperature contrasts between equator and poles.
Summer:
Weaker and shift poleward as temperature contrast decreases.
Example: The Subtropical Westerly Jet (STWJ) shifts northward in summer, allowing monsoonal easterlies to dominate peninsular India.
Jet Streams and the Indian Monsoon
The Tropical Easterly Jet (TEJ) over the Indian Ocean influences the onset and intensity of the southwest monsoon.
The Subtropical Westerly Jet (STWJ) retreats northward before monsoon onset; its delayed withdrawal can hamper monsoon progress.
Fact: The strength of the TEJ correlates with rainfall in central and southern India.
Jet Streams and Modern Aviation
Jet streams have both beneficial and hazardous implications for aviation:
Benefits for Aviation
Reduced Flight Time & Fuel Consumption:
Aircraft travelling from west to east (e.g., New York to London) ride tailwinds in jet streams, reducing flight time by up to 1 hour.
Example: In February 2020, a British Airways Boeing 747 broke the transatlantic speed record—flying at 1327 km/h due to a strong jet stream aided by Storm Ciara.
Economic Savings:
Utilising jet streams optimally can lead to significant fuel savings and reduced carbon emissions.
Navigation Efficiency:
Flight paths are charted using real-time meteorological data to harness jet stream winds efficiently.
Hazards for Aviation
Turbulence:
Clear Air Turbulence (CAT) is common near jet stream boundaries, especially in the jet streak exit region.
It occurs in cloudless skies and is difficult to detect.
Flight Delays:
Westbound flights (e.g., Delhi to London) face strong headwinds, leading to increased travel time and fuel usage.
Weather Disturbances:
Jet streams can steer cyclonic systems, which may disrupt air traffic patterns.
Fact: Turbulence caused by jet streams costs airlines approximately $100–150 million annually in repairs and delays (FAA estimates).
Jet streams are vital components of Earth’s atmospheric circulation, deeply influencing weather patterns, climatic systems, and aviation logistics. Their formation is rooted in thermodynamic and dynamic principles, and their variability has global implications—from the Indian monsoon to transcontinental flight efficiency. While aviation benefits substantially from harnessing jet streams, it must also address associated challenges like turbulence and fuel inefficiency on westbound routes. Thus, understanding jet streams is crucial for climate science, meteorology, and global connectivity.
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