CONCEPTS

# What is the humidity?

We explain what humidity is, what types exist and how it is measured. In addition, humidity in the weather and how clouds form.

1. ### What is the humidity?

Humidity is the amount of water vapor that the air contains . There is always water vapor in the air and the amount varies according to various factors, for example, if it has just rained, if it is near the sea, whether or not there is vegetation on the ground, the air temperature , among others.

This means that any place that has a presence of water with the possibility of heating and evaporating is a source of moisture , such as that which comes from the surface of rivers, lakes, wetlands and plants , where water can occur in solid state (frozen), liquid and gas (vapor).

1. ### Humidity in the climate

The climate is the result of numerous factors that act together. Geographical accidents, such as mountains and seas, have a decisive influence on their characteristics. Therefore, to determine the climate it is essential to analyze the temperature, air pressure and humidity .

Hygrometry is the part of physics that studies the causes of moisture in the atmosphere and the measure of its variations. Its name derives from the Greek, hygroscopy , higro which means “wet” and scopia which means “examination”.

1. ### Moisture types

The types of humidity can be:

• RH. It is the ability of the air to store water, which depends on the saturation point (limit of that air to hold water) and a certain temperature. Its calculation is defined by the ratio between the amount of steam present in the atmosphere, divided by the maximum amount it could contain, multiplied by one hundred (and the result is expressed as a percentage). A relative humidity of 100% indicates that it has reached its saturation limit point and, from there, all surplus water vapor condenses (becomes liquid).
• Absolute humidity It is the mass of water vapor that is present in a certain volume of air, before it is condensed (relative humidity). It is important to note that the temperature conditions absolute humidity: hot air masses have a greater capacity to store water vapor than cold air masses. Absolute humidity is expressed in grams per cubic meter.

The difference between relative humidity and absolute humidity is that the first corresponds to a percentage measure (how much percent of the water that the air can contain is stored there), and the second corresponds to a measure of the amount of water in weight that contains the air (calculated in grams or kilograms).

1. ### Humidity sensor

Humidity can be measured with sensors. Among them, they stand out:

• The hygrometer It allows determining the degree of humidity of the air or other gases. In meteorology, it measures the moisture content in the atmosphere.
• The psychometer It allows to determine the amount of steam that must be added to humid air to saturate it, that is, it indirectly measures humidity.
1. ### Clouds

The clouds are formed by drops of water and other particles that are suspended in the air . These drops come from the condensation of water vapor. If there are clouds in the sky, a mass of moist air cooled enough to saturate and begin condensation.

If there is no presence of clouds, it does not mean that there is no humidity: the air always contains some water vapor, but sometimes it does not contain enough to condense.