What best defines the saturation temperature of water vapor in the atmosphere?

The saturation temperature of water vapor in the atmosphere is best defined by the dew-point temperature. This temperature represents the point at which air becomes saturated with moisture; that is, the temperature at which water vapor in the air begins to condense into liquid water. When the air temperature decreases to the dew point, the air can no longer hold all its water vapor, resulting in condensation, which is critical for understanding weather phenomena and humidity levels.

The other options, while related to temperature and humidity, do not specifically define the saturation point of water vapor in the same way. Absolute temperature refers to a measurement scale (Kelvin) that does not directly relate to moisture content. Wet-bulb temperature incorporates both temperature and humidity but primarily measures cooling potential due to evaporation rather than the saturation point of vapor. Dry-bulb temperature simply indicates the air temperature without considering moisture content. Thus, dew-point temperature is the most accurate descriptor of the saturation temperature of water vapor.