Prelims 2011 · archive
MediumThe jet aircraft 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?
Answer & explanation
Answer: (c) Both 1 and 2
Both statements are correct. The lower stratosphere is almost free of clouds and water vapour. Its temperature rises with height, so the air is stable and calm, with no convection currents. Weather and turbulence stay in the troposphere below, so jets fly smoothly.
- ✓ 1. The stratosphere holds very little water vapour and is nearly cloud- and weather-free. Clouds form mainly in the troposphere. The only clouds seen in the stratosphere are occasional polar stratospheric clouds in its lowest, coldest altitudes.
- ✓ 2. Temperature increases with height in the stratosphere because ozone absorbs ultraviolet radiation. With warmer air lying over colder air, the layer is stable, so convective currents (vertical winds) do not develop. Gas movements are slow and the air is calm, unlike in the turbulent troposphere.
- ✗ (d) Both statements describe real features of the lower stratosphere, so 'Neither' is wrong.
- ✗ (a) Choosing 1 only ignores the stable, calm air of the stratosphere. The temperature inversion and the absence of convection are the second reason for the smooth ride.
Remember · The stratosphere is a stable, calm layer. It has very little water vapour, almost no clouds and no convectional currents. Weather and turbulence stay in the troposphere, which is why jets fly smoothly in the lower stratosphere.
Sources
- NASA Science – Earth's Atmosphere: A Multi-layered Cake ↗ “The stratosphere is nearly cloud- and weather-free, but polar stratospheric clouds are sometimes present in its lowest, coldest altitudes. It’s also the highest part of the atmosphere that jet planes can reach.”
- US National Weather Service (Shreveport) – Layers of the Atmosphere, Teacher's Guide ↗ “This layer holds 19 percent of the atmosphere's gases but very little water vapor. … The increasing temperature also makes it a calm layer with movements of the gases slow.”
Question: UPSC Civil Services (Preliminary) 2011, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·