Question

Consider the statements regarding Water Vapor and Dust:

I. The amount of water vapor increases as one moves from the equator toward the poles.

II. Dust particles are typically found closest to the Earth's surface.

III. Water vapor helps maintain Earth's temperature by trapping terrestrial radiation.

Which of the following is/are true?

• A. II and III only
• B. I and II only
• C. I and III only
• D. II only

Answer 1

Answer:

A. II and III only

Atmospheric Composition: Water Vapor and Dust

Water Vapor Distribution:

• The concentration of water vapor in the atmosphere is not uniform.
• It is highest in the tropics (near the equator) and decreases significantly as one moves towards the poles. This is due to higher temperatures near the equator leading to more evaporation.
• Therefore, statement I, which suggests an increase in water vapor towards the poles, is incorrect.

Dust Particles in the Atmosphere:

• Dust particles, along with other aerosols like salt, smoke, and pollutants, are a crucial component of the atmosphere.
• These particles are generally found in the lower atmosphere, primarily in the troposphere, because they originate from surface sources (like soil erosion, volcanic eruptions, and human activities).
• While some particles can be transported to higher altitudes, their highest concentration is typically closest to the Earth's surface.
• Therefore, statement II, indicating that dust particles are closest to the Earth's surface, is correct.

Role of Water Vapor in Temperature Regulation:

• Water vapor is a potent greenhouse gas.
• It plays a vital role in maintaining the Earth's temperature by absorbing and re-emitting terrestrial radiation (heat radiated from the Earth's surface).
• This process traps heat in the atmosphere, preventing it from escaping directly into space, thus contributing to the Earth's overall warmth. This is often referred to as the natural greenhouse effect.
• Therefore, statement III, highlighting water vapor's role in trapping terrestrial radiation, is correct.