Which layer of the atmosphere has the lowest temperature?
2023
Which layer of the atmosphere has the lowest temperature?
Answer: C. mesosphere — Concept: The atmosphere is divided into layers by the way its temperature changes with height. Inside any one layer the temperature moves in a single…
- A.
stratosphere
- B.
troposphere
- C.
mesosphere
- D.
More than one of the above
- E.
None of the above
Attempted by 50 students.
Show answer & explanation
Correct answer: C
Concept: The atmosphere is divided into layers by the way its temperature changes with height. Inside any one layer the temperature moves in a single consistent direction — falling in some layers, rising in others — so the boundary at the top of each layer (the tropopause, the stratopause, the mesopause) is a turning point at which that layer reaches its extreme temperature. To find the coldest layer, therefore, compare the layers' turning-point temperatures, not their heights.
Application: Reading the three named layers upwards from the ground:
Layer | Approximate height | Temperature as height increases | Temperature at its upper boundary |
|---|---|---|---|
Troposphere | surface to about 8–18 km | falls, at roughly 6.5 °C per km | about −60 °C at the tropopause |
Stratosphere | about 18–50 km | rises, because ozone absorbs ultraviolet radiation | about −3 °C at the stratopause |
Mesosphere | about 50–85 km | falls, as it absorbs very little solar radiation while its carbon dioxide radiates energy to space | about −90 °C at the mesopause |
Cross-check: Set the three turning-point values side by side: −60 °C, −3 °C and −90 °C. The mesopause value is the lowest of the three, and it is in fact the coldest region of the whole atmosphere; above it the thermosphere warms sharply again because its extremely thin gas absorbs high-energy solar radiation. Exactly one of the named layers therefore holds the minimum, so neither “more than one of the above” nor “none of the above” fits.
Answer: the mesosphere, whose upper boundary — the mesopause, near 85 km — is the coldest part of the atmosphere at about −90 °C.