What happens to the relative humidity if the temperature decreases and the dew point stays the same? Why?
1 Answer
It increases
Explanation:
Relative humidity is the ratio of the actual water vapor to the total amount of water vapor the air can hold. The total amount of water vapor the air can hold is based on the temperature of the air. So if the air cools the total amount of water vapor it can hold drops and therefore the relative humidity increases.
This chart shows the amount of water in grams on the side and the temperature on the bottom. At 20 degrees C the air can hold 16 grams of water per kilogram of air. At that point it is 100% relative humidity. If the amount is only 8 grams then the relative humidity is 50%.
So if the temperature is 25 degrees and the relative humidity is 50% (10 grams of water per kilogram of air) and the temperature drops to 15 degrees without any removal of water vapor (so still 10 grams), the relative humidity increases to 100%
