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Q74 (IAS/2012) Geography › World Physical Geography › Atmospheric structure Answer Verified

Normally, the temperature decreases with the increase in height from the Earth’s surface, because 1. the atmosphere can be heated upwards only from the Earth’s surface 2. there is more moisture in the upper atmosphere 3. the air is less dense in the upper atmosphere Select the correct answer using the codes given below :

Result
Your answer:  ·  Correct: C
Explanation

The temperature decrease with altitude in the troposphere, known as the normal lapse rate, is primarily due to two factors. First, the atmosphere is mainly heated from below by the Earth's surface through conduction and radiation [2]. As air moves away from this heat source, it cools. Second, air density and pressure decrease with height. When air rises, it expands due to lower pressure, which leads to internal cooling through adiabatic processes. Statement 2 is incorrect because moisture content actually decreases with height; the upper atmosphere is drier, and the presence of moisture (latent heat) would actually slow down the rate of cooling rather than cause it [5]. Therefore, only statements 1 and 3 are correct explanations for the normal decrease in temperature with altitude.

Sources

  1. [2] https://www.sciencedirect.com/topics/earth-and-planetary-sciences/troposphere
  2. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 22: Vertical Distribution of Temperature > Dry Adiabatic Lapse Rate (DALR) > p. 298
  3. [5] https://www.weather.gov/source/zhu/ZHU_Training_Page/thunderstorm_stuff/Thunderstorms/thunderstorms.htm
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