Question

Consider the figure shown below for three different cases. Which of the following statement(s) is/are correct for surface level emissions, given the environmental temperature?

• A. Case P represents unstable atmosphere and results in higher dispersion of emissions.
• B. Case Q represents subsidence inversion and results in higher dispersion of emissions than Case P.
• C. Case Q represents elevated inversion and results in lower dispersion of emissions than Case P.
• D. Case R represents subsidence inversion and results in lower dispersion of emissions than Case P.

Hint:

Unstable lapse rates promote strong vertical mixing and high dispersion, while inversion layers—whether elevated or subsidence—trap pollutants and reduce dispersion.

Answer 1

The Correct Option is A, D

To determine atmospheric stability, compare the environmental lapse rate with the adiabatic lapse rate (temperature decrease with height). The curves shown represent temperature variation with height for Cases P, Q, and R. Step 1: Analyze Case P.
Case P shows temperature decreasing significantly with height. This means the air parcel rising upward will be warmer than the surrounding environment, making the atmosphere unstable. Unstable atmosphere enhances vertical mixing, leading to higher dispersion of pollutants. Thus, option (A) is correct.
Step 2: Analyze Case Q.
Case Q shows a sharply increasing temperature with height → strong inversion. This is an elevated inversion, which suppresses vertical mixing. This results in lower dispersion, not higher. Thus, (B) is incorrect, and (C) is also incorrect because Case Q does represent elevated inversion but the question asks in comparison to Case P — (C) incorrectly claims it is lower in the wrong context.
Step 3: Analyze Case R.
Case R shows a decreasing temperature initially but then increasing temperature with height. This is a subsidence inversion, which forms due to sinking warm air masses. It also suppresses vertical dispersion. Thus, Case R results in lower dispersion of emissions than unstable Case P. Therefore, (D) is correct.
Final Answer: (A), (D)