Final answer:
The relative humidity of air can be increased either by adding moisture to the air or by decreasing its temperature. Adding moisture increases water vapor content, whereas decreasing temperature lowers the air's capacity to hold water vapor, thus increasing relative humidity percentage compared to its maximum capacity. Therefore, the correct answer is 2) By decreasing the temperature of the air.
Step-by-step explanation:
Two different ways that the relative humidity of a parcel of air can be increased are:
- By adding moisture to the air.
- By decreasing the temperature of the air.
The concept of relative humidity is important as it indicates the quantity of water vapor that the air currently contains in relation to the maximum it can hold at that temperature. When you add moisture to the air, it increases the water vapor content hence raising the relative humidity.
Conversely, by decreasing the temperature of the air, the capacity to hold water vapor drops, and therefore, without adding or removing water, the relative humidity percentage increases.
It is critical to note that relative humidity is not increased by raising temperature or by lowering pressure, as higher temperatures allow the air to hold more moisture, and lower pressures can lead to increased evaporation, thus reducing relative humidity.