Author Question: Define relative humidity and dew point, and then explain why the latter is a better indicator of ... (Read 54 times)

DyllonKazuo · **on:** Jul 14, 2018

Define relative humidity and dew point, and then explain why the latter is a better indicator of water vapor content.

What will be an ideal response?

Question 2

What is specific humidity and why is it such a useful measure of water vapor content?

What will be an ideal response?

elizabethrperez · **Reply #1 on:** Jul 14, 2018

Answer to Question 1

Answer: Relative humidity: relates the amount of water vapor in the air to the maximum possible at the current temperature. The World Meteorological Organization defines the relative humidity as
RH = (mixing ratio/saturation mixing ratio) x 100. Because of its dependence on temperature, the relative humidity will change throughout the course of the day even if the amount of moisture in the air is unchanged. Dew point: the temperature at which saturation occurs. It is a simple index to use and easy to interpret. And it is dependent almost exclusively on the amount of water vapor present.

Answer to Question 2

Answer: Specific humidity expresses the mass of water vapor existing in a given mass of air. Specific humidity has the advantage of not changing as air expands or contracts. When a kilogram of air expands, its mass is unchanged (it is still 1 kg), and the proportion that is water vapor is unchanged. As a result, the specific humidity is unaffected. Likewise, specific humidity is not temperature dependent. If a kilogram of air contains 1 g of water vapor, it still contains 1 g after heating. For this reason, specific humidity is a good indicator for comparing water vapor in the air at different locations whose air temperatures might be different from each other.