RAS question
Inversion of temperature occurs when:
Correct answer: (D) Temperature increases with altitude instead of decreasing.
Temperature inversion occurs when temperature increases with altitude instead of decreasing.
Explanation
Temperature inversion is the reversal of the usual vertical pattern of temperature. The NOAA/NCEI algorithm document defines an inversion as a region of the atmosphere where temperature increases with height; in such conditions, the normal relationship between temperature and height no longer works in the usual way. That is exactly why option D is right: the key test is not that the air merely cools, or that pressure changes, but that higher air is warmer than the air below it. In geography, a warm layer above cooler air suppresses vertical movement, so pollutants can remain trapped, especially in winter valley or basin conditions such as Delhi smog episodes.
Why the other options are wrong
- (A) A rapid fall in temperature describes cooling, not inversion, because inversion specifically requires temperature to rise with height.
- (B) Pressure increasing with height is not the defining feature here; the question is about the vertical temperature pattern, not pressure.
- (C) A reversal of wind direction is a wind-pattern change, while temperature inversion is defined by warmer air lying above cooler air.
Concept
This tests the climatology concept of lapse rate and its reversal. It recurs in RAS because inversion links physical geography with winter smog, valley climates and urban air-pollution questions.