Final answer:
Evaporation and transpiration are processes that increase humidity by adding water vapor to the atmosphere. High humidity can lead to a reduced rate of these processes due to a smaller difference in water vapor pressure.
Step-by-step explanation:
The processes that would lead to an increase in humidity include evaporation and transpiration. Evaporation is the process where liquid water is converted into water vapor and added to the atmosphere. Transpiration occurs when plants release water vapor into the air through their leaves. When these processes contribute more water vapor into the air, the humidity increases. Conversely, condensation would decrease humidity by converting water vapor back into liquid form.
It's important to note that high humidity can actually reduce the rate of evaporation and transpiration because the difference in water vapor pressure between the leaf and the atmosphere decreases. This means on humid days, water will evaporate more slowly from surfaces or transpire less quickly from plants compared to dry days.