GATE CE 2017 Set 2 — Question 9
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Environmental Engineering → Air Pollution
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Question
Following observations have been made for the elevation and temperature to ascertain the stability of the atmosphere:
The atmosphere is classified as
| Elevation (in m) | Temperature (in C) |
|---|---|
| 10 | 15.5 |
| 60 | 15.0 |
| 130 | 14.3 |
Correct answer
(B) Unstable
Solution
To classify the stability of the atmosphere, we calculate the Environmental Lapse Rate (ELR) and compare it with the Dry Adiabatic Lapse Rate (DALR).
The observed ELR is .
1.Calculate ELR:
The lapse rate is defined as the rate of decrease of temperature with height: .- Between 10 m and 60 m:
- Between 60 m and 130 m:
The observed ELR is .
2.Compare with DALR:
The standard Dry Adiabatic Lapse Rate (DALR) is approximately .3.Classification:
- Since (), the atmosphere is super-adiabatic.
- In a super-adiabatic environment, a parcel of air that is displaced upwards will continue to rise because it remains warmer (and thus less dense) than the surrounding air. This condition is defined as Unstable.
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