Humidity definitions and measurement devices

In summary, there are three definitions of humidity: absolute, relative, and specific. When measured as a percentage, it is typically referring to relative humidity, which compares the actual water content to the maximum water content at a given temperature. In non-tropical climates, 100% usually means it is raining, but in tropical climates, it can be as high as 95-100% without rain. The amount of moisture air can hold as invisible vapor is affected by air temperature and pressure.
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Delta2
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I know there are three definitions of humidity. Absolute , relative and specific. Can you tell me if on a typical commercial device (such as the one i have in a clock i have) that measures humidity as percentage is it the relative humidity that it measures? Can the percentage become greater than 100%?
 
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Delta² said:
Can you tell me if on a typical commercial device (such as the one i have in a clock i have) that measures humidity as percentage is it the relative humidity that it measures?

When measured as a percentage, its a reference to RH - relative humidity its measuring the relative difference between absolute humidity ( actual water content) and the maximum water content that the air can have at a given temperature

Delta² said:
Can the percentage become greater than 100%?

not that I have ever seen or heard of

... in non tropical climates, 100% would usually mean its raining. In tropical climates, I have often seen 95 - 100% and still not raining, but ohhhh gosh, the air is just so unbearable and "sticky"
Air temperature and pressure have a large bearing on this

It never ceases to amaze me how much moisture the air can hold as invisible vapour

Dave
 
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davenn said:
relative humidity its measuring the relative difference between absolute humidity ( actual water content) and the maximum water content that the air can have at a given temperature

More precisely, it's the ratio of the water vapor partial pressure in the air to the equilibrium vapor pressure of water at the air temperature.

Chet
 
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Likes davenn
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LOL yup ... didn't want to go too deep :wink:
 

1. What is humidity and why is it important in scientific research?

Humidity refers to the amount of water vapor present in the air. It is an important factor in scientific research as it can affect various processes such as chemical reactions, plant growth, and weather patterns. It is also crucial in determining the comfort level and health of humans and other living organisms.

2. What is the difference between relative humidity and absolute humidity?

Relative humidity is the ratio of water vapor present in the air to the maximum amount of water vapor that can be held at a specific temperature. It is expressed as a percentage and is dependent on temperature. Absolute humidity, on the other hand, is the actual amount of water vapor present in the air regardless of temperature. It is expressed in grams of water vapor per cubic meter of air.

3. How is humidity measured?

Humidity can be measured using various devices such as a hygrometer, psychrometer, or a dew point monitor. These instruments work by either measuring the change in electrical resistance of materials in response to humidity or by using a wet and dry bulb thermometer to calculate relative humidity.

4. What is a dew point and why is it important?

Dew point is the temperature at which water vapor in the air condenses into liquid water. It is an important measure of humidity as it indicates the point at which water vapor begins to form dew or fog. It is also a good indicator of how comfortable the air will feel, as higher dew points can lead to a feeling of stickiness.

5. How does humidity affect air quality?

High humidity can contribute to poor air quality by promoting the growth of mold, bacteria, and other harmful organisms. It can also increase the concentration of pollutants in the air, as water vapor can act as a carrier for these particles. Low humidity, on the other hand, can cause dryness and irritation in the respiratory system, making it easier for pollutants to enter the body.

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