Avielevate / DGCA CPL papers / Aviation Meteorology / JETSTREAM
JETSTREAM — DGCA CPL Aviation Meteorology
Chapter J15 of the Aviation Meteorology paper. 25 practice questions in the Avielevate bank, every one with its answer key, filterable into a timed set on this chapter alone.
What this chapter covers
The learning objectives we file JETSTREAM questions under, and how many sit behind each. These come straight out of the bank and are regenerated whenever it changes — they are what is there today, not a claim.
| Learning objective | In the bank |
|---|
| __GEN__ General | 25 questions |
Sample JETSTREAM questions, answered and explained
Real questions from this chapter, with the answer marked and the reasoning written out — the same explanations you get inside the app.
0324013 · JETSTREAM
The vertical wind shear in a jet stream is about:
- A5m/s/ km
- B6m/s/km
- C8m/s/km
Why that is the answer
**Concept**
A **jet stream** is a narrow, fast-moving band of wind, usually found just below the tropopause. **Wind shear** is a change of wind speed or direction over a distance. In a jet the wind changes quickly both with height (**vertical shear**) and sideways (**horizontal shear**).
**Explanation**
The World Meteorological Organization (WMO) describes a jet stream as a strong, narrow current with:
- a core speed of at least **60 kt** (about 30 m/s)
- a **vertical wind shear** of the order of **5 to 10 m/s per km** of height
- a horizontal (lateral) wind shear of about **5 m/s per 100 km**
A jet forms where cold polar air and warm tropical air meet, because a strong horizontal temperature contrast makes the wind increase with height. The speed rises up to the core, just below the tropopause, and falls off again above and below it. Look at the diagram: the speed drops from about 110 kt at the core to 60 kt at the edge over about 6 km of height, roughly 5 m/s for every kilometre.
This shear is what causes **clear air turbulence (CAT)**, which is most common on the polar (cold) side of the jet, just above and below the core.
**Applying it to the question**
Using the standard value, the vertical wind shear in a jet stream is about **5 m/s/km**.
**Remember for DGCA:** jet stream = 60 kt or more, vertical shear about 5 m/s per km, horizontal shear about 5 m/s per 100 km.
0324019 · JETSTREAM
The lower limit of jet core speed assigned by the WMO is:
- A60 kt
- B60 m/s
- C70 m/s
Why that is the answer
**Concept**
Not every strong upper wind is a **jet stream**. The **WMO** (World Meteorological Organization) defines a jet stream as a strong, narrow current concentrated along a nearly horizontal axis in the upper troposphere or lower stratosphere, with strong vertical and horizontal wind shear. It also sets a **lower limit** for the speed along the axis: **60 kt** (about 30 m/s).
**Explanation**
Check the units, since the options mix knots and metres per second:
- 1 kt = 1 nautical mile per hour = 1,852 m in 3,600 s, about **0.514 m/s**.
- 60 kt × 0.514 = about **31 m/s**, so 60 kt and 30 m/s describe the same limit. A speed of 60 m/s would be about 117 kt, far above the minimum.
Typical jet cores carry 80 to 150 kt, and the strongest winter jets over Japan can exceed 200 kt. Look at the diagram: the outer isotach marks 60 kt, the edge of what counts as the jet, with faster winds towards the core.
The WMO also describes the typical shear in a jet: about 5 m/s per km vertically and about 5 m/s per 100 km horizontally.
**Applying it to the question**
The lower limit of jet core speed assigned by the WMO is **60 kt**.
**Remember for DGCA:** jet stream = 60 kt or more (about 30 m/s) along its axis.
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Frequently asked
How many JETSTREAM questions are there for the DGCA CPL Aviation Meteorology paper?
Avielevate's bank carries 25 published JETSTREAM questions for Aviation Meteorology, mapped across 1 learning objective. Every one has its answer key, and explanations are being written across the whole bank.
How much of the Aviation Meteorology paper is JETSTREAM?
The DGCA does not publish a per-chapter breakdown of its papers, so nobody can honestly tell you — and we will not guess. What we can tell you is what students who have just sat a paper reported meeting, which is measured rather than rumoured: that is the exam recall report inside the app.
What is the best way to revise JETSTREAM?
Sit a short timed set on this chapter alone, tag how sure you were of each answer, then drill the two that actually leak marks: the ones you got right while guessing, and the ones you got wrong while confident. Avielevate does that tagging for you and puts anything you got wrong back in front of you on a spaced schedule.
The rest of the Aviation Meteorology paper
One account covers every chapter of every paper.
← All Aviation Meteorology chapters · All six DGCA CPL papers