What is the humidity?

Generally speaking, the humidity is 100% when it is impossible to contain more water vapor in the air at the current temperature.

Absolute humidity is the pressure generated by water vapor in the air. There is an upper limit of absolute humidity at a certain temperature, which is called saturation pressure, and the saturation pressure increases with the increase of temperature. The saturated pressure of water vapor at 100℃ is 10 1kPa( 1 standard atmospheric pressure).

Relative humidity is the ratio of absolute humidity to saturated air pressure at current temperature.

Usually, humidity in weather forecast refers to relative humidity.

At a certain temperature, the less water vapor in a certain volume of air, the drier the air; The more water vapor, the wetter the air. In this sense, physical quantities such as absolute humidity, relative humidity, relative humidity, mixing ratio, saturation deficit and dew point are often used to express.

If the weight of liquid water in wet steam accounts for the percentage of the total weight of steam, it is called the humidity of steam.

Extended data:

At a certain temperature, a certain volume of air can only hold a certain amount of water vapor. If the amount of water vapor reaches the limit that air can hold water vapor, the air is saturated at this time, and the relative humidity is 100%. In a saturated state, water no longer evaporates.

In this hot summer weather, the sweat secreted by the human body is difficult to evaporate, and it feels sultry. On the other hand, autumn sometimes meets the "autumn tiger" with high temperature, but due to the obvious decrease of humidity, people are sweating all over but seldom feel "sultry".

If we encounter low temperature and high humidity in winter, people will feel wet and cold. Too low air humidity can also make people feel uncomfortable. When southerners first arrive in the north, coastal people often feel thirsty and even have nosebleeds when they go to the northwest. Of course, this is a question of human adaptability.

There are three basic forms of humidity, namely water vapor pressure, relative humidity and dew point temperature.

Water vapor pressure (once called absolute humidity) indicates the pressure of water vapor in the air, and the unit is hectopascals (hPa), with one decimal place reserved;

Relative humidity is expressed as the percentage of the ratio of actual water vapor pressure to saturated water vapor pressure in the air at the current temperature, taking an integer;

Dew point temperature refers to the temperature when the water vapor content in the air and the air pressure reach saturation during cooling. Units are expressed in degrees Celsius (℃), with one decimal place reserved. When equipped with a hygrometer, it can also measure the continuous record of relative humidity and minimum relative humidity.

References:

Baidu encyclopedia-air humidity