Examkin

Question

Difficulty: MediumAtmosphere and Weather

As evening approaches, the ambient air temperature over a grassy field cools until it reaches the dew point, bringing the relative humidity of the air to 100%. Which atmospheric process occurs as a direct result of reaching this saturation point?

  1. A
    Heat is conducted directly from the cooler air into the warmer ground below.
  2. Water vapor condenses out of the saturated air to form liquid water droplets.Answer
  3. C
    Liquid water on the surface rapidly evaporates into the saturated air mass.
  4. D
    The cooled air parcel rises rapidly to generate a localized low-pressure system.

Answer

Water vapor condenses out of the saturated air to form liquid water droplets.
The correct answer is that water vapor condenses out of the saturated air to form liquid water droplets. The dew point is defined as the temperature at which a parcel of air reaches 100%100\% relative humidity (saturation). When the air cools to this threshold, the air parcel can no longer hold all of its water in the vapor state, forcing the excess moisture to undergo condensation into liquid water droplets (such as dew or fog).

Step-by-Step Solution

1
Analyze the relationship between air temperature, dew point, and relative humidity.
When air temperature cools to the dew point, the relative humidity reaches 100%100\%, meaning the air is completely saturated with moisture.
Dew point represents the temperature to which air must be cooled at constant pressure to become fully saturated with water vapor.
2
Determine the thermodynamic phase change that occurs upon reaching saturation.
Excess water vapor undergoes a phase transition from gas to liquid (condensation), producing dew on surfaces or suspended droplets (fog/clouds).
Air at or below its dew point cannot maintain water in the gaseous phase above its saturation vapor pressure.

Key Concept

Dew point temperature and atmospheric moisture saturation causing condensation
Estimated Time:1m 0s
Rate this question

Topics

Atmosphere and Weather

More questions from this topic