Humidity / humidity is defined as the proportion of water vapor in the air. Conceptually, several terms have to be distinguished from each other:
Absolute humidity: indicates how many grams of water per cubic meter (m³) of air are contained (water vapor density).
Maximum humidity: indicates how many grams of water per cubic meter (m³), taking into account the maximum temperature, can be recorded. The maximum humidity always corresponds to 100% of the relative humidity.
Relative humidity: indicates the saturation ratio of the air, taking into account the temperature, in percent (%). A humidity of 100% means that the air is maximally saturated. The relative humidity results from the division of absolute humidity and the maximum air humidity.
The humidity in the formation of the weather plays a not insignificant role. With a hygrometer (ancient Greek hygros = "damp" and metron = "scale") meteorologists measure the humidity. Condensation processes (see: state of matter) are related to the formation of clouds, dew or fog.
Humidity and temperature
How much water vapor the air can absorb depends on the air temperature. Warm air can absorb more water than cold air. The diagram on the right shows this clearly. On the abscissa (X-axis) is the temperature, on the ordinate (Y-axis), the water content is entered in g / m³. With increasing temperature, air can absorb more water vapor. And this relationship does not grow linearly, but exponentially. If the air is supersaturated, ie more water molecules are present than could be absorbed, the excess water condenses and settles. As a result, the relative humidity remains at a maximum of 100%.
One cubic meter of air can absorb a maximum of x grams of water at the following ambient temperatures:
0 ° C about 5g of water
10 ° C approx. 9g water
20 ° C approx. 17g water
30 ° C approx. 30g water
40 ° C approx. 50g water
50 ° C approx. 80g water
60 ° C approx. 120g water
80 ° C approx. 300g water
100 ° C approx. 580g water