______ are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere. Their speed varies from about 110 km/h in summer to about 184 km/h in winter.
Jet Streams
Understanding High-Altitude Atmospheric Winds
The question asks to identify a specific type of atmospheric wind characterized by its high altitude, westerly direction, presence in the troposphere, and varying speed between summer and winter.
Characteristics of High-Altitude Winds
Let's break down the key features mentioned in the question:
- Altitude: Above 12,000 meters. This is very high in the atmosphere, typically in the upper troposphere or lower stratosphere.
- Direction: Westerly winds. This means they blow from west to east.
- Location: Troposphere. This is the lowest layer of Earth's atmosphere where most weather occurs.
- Form: Narrow belt. This suggests a concentrated flow rather than a diffuse one.
- Speed: High speed, varying from about 110 km/h in summer to about 184 km/h in winter. This indicates a strong wind system.
Analyzing the Options
Now let's consider the provided options and see which one matches these characteristics:
- Jet Streams: Jet streams are known as narrow, fast-flowing, high-altitude, westerly air currents in the atmospheres of some planets, including Earth. Earth's major jet streams are located near the top of the troposphere. Their speed does vary significantly with the season, being generally stronger in winter due to larger temperature differences. This description aligns perfectly with all the characteristics mentioned in the question.
- Whirlwind: A whirlwind is a small parcel of air that rotates around a vertical axis. Examples include dust devils and similar small-scale atmospheric vortices. They are typically low-altitude phenomena and do not fit the description of a high-altitude belt of wind.
- Derecho: A derecho is a widespread, long-lived straight-line wind storm associated with a fast-moving group of severe thunderstorms. While powerful, they are surface or low-altitude weather events, not high-altitude wind belts.
- Hurricane: A hurricane (or tropical cyclone) is a large rotating storm system characterized by a low-pressure center, strong winds, and thunderstorms that produces heavy rain. Hurricanes form over warm ocean waters and are large-scale, low-altitude weather systems, not high-altitude wind belts.
Conclusion
Comparing the description in the question with the definitions of the options, it is clear that the term that fits is Jet Streams. They are specifically defined by their high altitude in the troposphere, westerly direction, narrow belt formation, and high, varying speeds.
| Feature | Description in Question | Jet Streams | Whirlwind | Derecho | Hurricane |
|---|---|---|---|---|---|
| Altitude | Above 12,000 m (Troposphere) | High (Upper Troposphere) | Low | Low/Surface | Low/Surface |
| Form | Narrow belt | Narrow belt | Small, rotating column | Widespread storm winds | Large rotating system |
| Direction | Westerly | Westerly | Variable/Rotating | Straight-line (surface) | Rotating (surface) |
| Speed | 110-184 km/h (Varies) | High (Varies seasonally) | Low to Moderate | High (Surface) | Very High (Surface) |
Revision Table: Key Atmospheric Terms
| Term | Brief Description | Typical Location/Altitude |
|---|---|---|
| Jet Stream | Fast-flowing, narrow, westerly air currents | Upper troposphere/Lower stratosphere |
| Troposphere | Lowest layer of Earth's atmosphere where weather occurs | Surface up to ∼7-15 km |
| Westerly Winds | Winds blowing from west to east | Various altitudes, characteristic of mid-latitudes |
| Whirlwind | Small rotating column of air | Low altitude/Surface |
| Derecho | Widespread, straight-line wind storm | Surface/Low altitude |
| Hurricane | Large tropical cyclone | Surface/Low altitude over warm oceans |
Additional Information on Jet Streams
Jet streams are a crucial part of the global atmospheric circulation. They form at boundaries between air masses of different temperatures, primarily along pressure gradients. The larger the temperature difference, the stronger the jet stream.
- There are typically four main jet streams on Earth: two polar jet streams and two subtropical jet streams.
- The polar jet stream is usually located between 50° and 60° latitude and is stronger and found at a lower altitude than the subtropical jet stream.
- The subtropical jet stream is located around 30° latitude and is generally weaker.
- Jet streams influence weather patterns significantly by steering storms and affecting temperature boundaries.
- Aircraft often use jet streams to save fuel and time when flying eastbound.
Important Questions from Climatology
In the context of climate, what is the full form of ITCZ?
With reference to the climatic conditions of the Prairies, which of the following statements is correct?
Land and sea breeze are caused due to _____________
Which island emerged in the Bay of Bengal in the after math of the Bhola cyclone in 1970?
In India, during October-November, with the apparent movement of the sun towards the south, the ______ over the northern plains becomes weaker.
