What happens to the relative humidity of a parcel of air when it becomes saturated?

When a parcel of air becomes saturated, its relative humidity reaches 100%. Relative humidity is defined as the amount of water vapor present in the air compared to the maximum amount of water vapor the air can hold at a given temperature. When saturation is achieved, the air cannot hold any more moisture, meaning the relative humidity must be at its maximum of 100%. This is critical in understanding weather patterns and phenomena such as cloud formation and precipitation, as saturation plays a significant role in these processes.

In contrast, other options fail to recognize the nature of saturation and the definition of relative humidity. For example, a decrease in relative humidity would imply that the air can still hold more moisture, which contradicts the concept of saturation. Similarly, if relative humidity were to increase beyond 100%, it would indicate that the air has exceeded its capacity to hold moisture, which is not possible in a saturated state. Fluctuations in relative humidity would mean it is changing over time, but once saturation is reached, it stabilizes at that maximum value.