Question

What happens to the relative humidity if the temperature decreases and the dew point stays the same? Why?

Answer 1

Hint: The relative humidity is the fraction of the actual water vapor to the total amount of water vapor the air can contain. The total amount of water vapor that the air can carry depends on the temperature of the air. So, if the air chills the total amount of water vapor, it can hold drops, and hence the relative humidity rises.

Complete step-by-step solution:
The relative humidity depends on temperature, and it is the ratio of the actual water vapor to the total amount of water vapor the air can contain. The total amount of water vapor depends on the temperature of the air. The dew point is the temperature measurement to which the atmosphere would have to be cooled to convert saturated. When moisture is high, the dew point temperature is only a few degrees below, or equal to, air temperature and it is not changed by a variation in air temperature and does not hesitate much throughout the day.
Suppose the water vapor remains the same and the temperature falls, the relative humidity rises. If the water vapor remains the same and the temperature increases, the relative humidity decreases because cooler air does not need as much moisture to convert saturated as more heated air. In summer, the relative humidity is more in the morning than in the afternoon; This is because the colder morning air is nearer to saturation than the warm afternoon air, even with an equal amount of water vapor. However, there is no notable variation in regular average relative humidity between winter and summer. Since hot air is less dull than cool air, there is more vacancy for water vapor in hot summer air than cool winter air.
Hence, relative humidity increases if the temperature decreases and the dew point stays the same.
Additional Information: - The dew point is a more stable indicator of humidity than relative humidity because the dew point is not changed by a variation in air temperature and does not change much throughout the day. Under the dew point, water will condense outside of the air on surfaces. In the fresh and early morning, grass surfaces will be covered with water if the night temperature has fallen under the dew point.

Note: When the air temperature rises, and dew point temperature stays the same, relative humidity decreases. When the air temperature remains the same, and relative humidity rises, dew point temperature rises; when the air temperature is constant and relative humidity increments, actual vapor pressure increases.