UPSC Prelims 2011 · Question 35 of 100
UPSC Prelims 2011 question on Jet Aircraft Lower Stratosphere
- ExamUPSC CSE
- Year2011
- PaperGeneral Studies Paper I
- SubjectGeography
- TopicClimatology
- DifficultyHard
- TypeStatement
The jet aircrafts fly very easily and smoothly in the lower stratosphere. What could be the appropriate explanation?
1. There are no clouds or water vapour in the lower stratosphere.
2. There are no vertical winds in the lower stratosphere.
Which of the statements given above is/are correct in this context?
Show answer
Answer: C. Both 1 and 2
Verdict
Correct Answer: Both 1 and 2
Analysis
Jet aircraft fly smoothly in the lower stratosphere because this layer is generally dry, cloud-free and stable, with very little vertical air movement.
Statement by statement
1. There are no clouds or water vapour in the lower stratosphere — Correct
Most water vapour is found in the troposphere. The lower stratosphere is very dry, so cloud formation and weather disturbances are almost absent. This gives aircraft a clearer and more stable flying environment.
2. There are no vertical winds in the lower stratosphere — Correct
The stratosphere has a temperature inversion, where temperature increases with height due to ozone absorbing ultraviolet radiation. This makes the air stable and prevents convection. Hence, vertical winds and turbulence are very weak or absent.
Extra UPSC info
The troposphere is the lowest atmospheric layer and contains most weather phenomena.
The stratosphere lies above the troposphere and contains the ozone layer.
Commercial jets often cruise near the upper troposphere or lower stratosphere.
Thin air at high altitude reduces drag and improves fuel efficiency.
Rare polar stratospheric clouds may form near polar regions, but generally the lower stratosphere is considered cloud-free for exam purposes.
How to crack it
The lower stratosphere provides smooth flying conditions because it has very little moisture, almost no clouds and minimal vertical air movement. Therefore, both statements are correct.